Pressure-induced transformation of CH₃NH₃PbI₃: the role of the noble-gas pressure transmitting media

The photovoltaic perovskite, methyl­ammonium lead triiodide [CH₃NH₃PbI₃ (MAPbI₃)], is one of the most efficient materials for solar energy conversion. Various kinds of chemical and physical modifications have been applied to MAPbI₃ towards better understanding of the relation between composition, structure, electronic properties and energy conversion efficiency of this material. Pressure is a particularly useful tool, as it can substantially reduce the interatomic spacing in this relatively soft material and cause significant modifications to the electronic structure. Application of high pressure induces changes in the crystal symmetry up to a threshold level above which it leads to amorphization. Here, a detailed structural study of MAPbI₃ at high hydro­static pressures using Ne and Ar as pressure transmitting media is reported. Single-crystal X-ray diffraction experiments with synchrotron radiation at room temperature in the 0–20 GPa pressure range show that atoms of both gaseous media, Ne and Ar, are gradually incorporated into MAPbI₃, thus leading to marked structural changes of the material. Specifically, Ne stabilizes the high-pressure phase of Ne_xMAPbI₃ and prevents amorphization up to 20 GPa. After releasing the pressure, the crystal has the composition of Ne_0.97MAPbI₃, which remains stable under ambient conditions. In contrast, above 2.4 GPa, Ar accelerates an irreversible amorphization. The distinct impacts of Ne and Ar are attributed to differences in their chemical reactivity under pressure inside the restricted space between the PbI₆ octahedra.

1. Introduction

MAPbI₃ is currently considered as one of the most promising compounds in photovoltaic technologies for making cheap and highly efficient solar cells (Green et al., 2014; Weber et al., 2015). One of the hurdles which reduces the enthusiasm for practical applications of MAPbI₃ is its content of lead which confers toxicity on this material (Benmessaoud et al., 2016). Therefore, it would be highly desirable to replace lead with a non-toxic element, while still preserving the high light conversion efficiency. The conditio sine qua non for achieving this goal is a better understanding of the microscopic origin of this high energy conversion efficiency. There are opinions that the rotation or other type of motion of methyl­ammonium cations (MA) introduces a slightly indirect band gap in this material, which extends the lifetime of photoelectrons (Motta et al., 2015), helping them to flow out of the material as a current. Valuable information about the role of the cation can be obtained by studying its behaviour in the lattice under high pressure (Ou et al., 2016). The perovskite crystal structure of MAPbI₃ is very flexible due to a large interstitial space (of ∼8 Å in diameter), where the small (∼1.5 Å) linear cation is located. The PbI₆ octahedra and the cations interact via weak hydrogen bonds. The strength and the conformation of the hydrogen bonds can be influenced either by the presence of captured exogenous substances, such as water (Arakcheeva et al., 2016), or by external factors such as pressure or temperature, leading to changes in the symmetry of the unit cell. A recently published extended review (Lü et al., 2017) on the pressure-induced evolution of the structure and the physical properties of organic–inorganic halide perovskites demonstrates a poor reproducibility of the changes. This calls for more investigations to uncover the underlying mechanisms. Fig. 1 shows a schematic representation of the two major pressure-induced structural transformations in MAPbI₃, a phase transition and amorphization, reported in the literature together with the ones obtained in the present study. At very low pressures (0.1–0.3 GPa), a first-order phase transition from the tetragonal body-centred to the body-centred (pseudo) cubic unit cell takes place (Fig. 1, blue to red lines). The amorphization of the compound occurs after the structural phase transition (Fig. 1, black line). However, in different experiments the onset of the amorphization has been observed under different pressures, and the pressure transmitting medium (PTM) could be considered as a factor affecting the pressure-induced transformation of MAPbI₃ (Fig. 1). Such an effect has already been observed in organic compounds (Zakharov et al., 2016) and also in some minerals (Ardit et al., 2014; Sato et al., 2013; Guńka et al., 2015; Lobban et al., 2002). This provided the motivation for the present work on studying the influence of PTM on the structure of MAPbI₃. We have chosen two noble gaseous media, Ne and Ar, which are among the most hydro­static PTMs and have distinct atomic radii: Ne (0.38 Å) and Ar (0.71 Å). Single-crystal synchrotron X-ray diffraction (XRD) measurements provided a precise data set, which allowed structure determination as a function of pressure with the best precision. Surprisingly, we found that under high pressure both Ar and Ne were incorporated into the structure. Moreover, the pressure-induced phase of Ne_0.97MAPbI₃ remained stable and highly crystalline after decompression.

Figure 1 Schematic overview of the pressure-induced transformation of MAPbI3 at room temperature. Top panel: influence of the PTM on the transformation. The thickness of the red and black lines represents schematically the relative content of the (pseudo) cubic and amorphous phases shown, respectively, in the bottom panel. Bottom panel: relations between the unit cells of different phases. Unit-cell parameters: apr ≃ 6.4 Å for the primitive perovskite cubic cell (green line); a = b ≃ apr ≃ 8.8 Å and c ≃ 2apr ≃ 12.7 Å for the tetragonal body-centred cell (blue) under ambient condition; a ≃ b ≃ c ≃ 2apr ≃ 12.3 Å for the body-centred (pseudo)cubic cell (red) under high pressure. The data are taken from: Capitani et al. (2016) and Jaffe et al. (2016) for He; Ou et al. (2016) and Jiang et al. (2016) for no PTM (None); Jiang et al. (2016) for silicon oil (Si-oil); Wang et al. (2015) for non-specified PTM (Unknown); Szafrański & Katrusiak (2016) for propanol. Data corresponding to Ar and Ne (yellow background) are from the present work.

2. Experimental

2.1. Synthesis and crystallization

The preparation of MAPbI₃ single crystals has been reported elsewhere (Arakcheeva et al., 2016). Several crystals were initially tested for their crystal structure and crystal quality at ambient conditions. All of them showed the space group I422 crystal symmetry with the unit-cell parameters and the atomic coordinates identical to those reported by Arakcheeva et al. (2016). Preliminary diffraction measurements under high pressure showed as expected that the starting quality of the crystal (degree of mosaic and strains) has a significant effect on the high-pressure transformation (Fig. S1). Therefore, only the highest quality crystals have been selected for the final diffraction experiments.

2.2. Single-crystal synchrotron XRD experiments

Room-temperature (293 K) high-pressure (up to 20.27 GPa) XRD data were collected at the ID27 High Pressure Beamline of the European Synchrotron Radiation Facility (ESRF) in Grenoble. Diamond anvil cells were used with rhenium gaskets and Ne or Ar gases as the PTM to generate hydro­static conditions. The X-ray wavelength was set to 0.3738 Å. The minimal linear size of the crystals was about 10 µm. Diffraction data were recorded with a Mar165 CCD detector and the pressure was measured using the ruby fluorescence technique (Syassen, 2008). After decompression, additional measurements were conducted on the Ne-containing crystal to determine its structure under ambient conditions. CrysAlis PRO (Rigaku Oxford Diffraction, 2014) and JANA2006 (Petříček et al., 2014) software packages were used for data processing and structural refinement, respectively. Experimental details are listed in Tables S1 and S2 and are illustrated in Fig. 2 and also in Figs. S1, S2 and S3.

Figure 2 The XRD patterns illustrating the pressure-induced transformation of MAPbI3 with (a) Ne and (b) Ar as PTM. The powder XRD patterns calculated from the single-crystal experiments are presented at the logarithmic scale. Sections of the reciprocal space are shown for l = 0. The axes h, k (H, K) specific only for the tetragonal (pseudo-cubic) modification are emphasized in blue (red).

2.2.1. Structure determination

The general scheme of the structure determination is illustrated in Fig. 3 using the example of the crystal at ambient conditions and under 0.69 GPa up to 20.27 GPa pressures with Ne as the PTM. The starting (pristine) and the released (after exposure to the highest pressure) crystals are shown next to each other for comparison. The most probable symmetry of the structure at each pressure was determined by testing the inorganic framework for all possible space groups in all possible crystallographic systems (cubic, tetragonal, trigonal and ortho­rhombic). Next, after the refinement of the atomic positions of Pb and I [Fig. 3(a)], difference electron density maps were calculated for each case [Fig. 3(b)]. The pristine crystal can be characterized by the maxima in the expected MA positions [dark-blue circles in Fig. 3(b)]. These maxima are also perfectly identified at 0.69 GPa and for the released crystal, whereas they are absent at 20.27 GPa. However, even stronger and more localized maxima [cyan circles in Fig. 3(b)] are clearly visible for each pressure, with the exception of the starting (pristine) case. These additional maxima are attributed to Ne atoms, giving a compatible electron density contribution [Fig. 3(c)]. At 20.27 GPa, the usual MA positions show nearly zero electron density and only the Ne-attributed maxima are observable. We have to emphasize that these maxima could not be fitted with displaced MA cations. The schematic diagrams of the crystal structure for each pressure after including MA and/or Ne in the refined models are shown in Fig. 3(c). The residual electron density maps calculated after the refinements have values close to zero [Fig. 3(d)], this supports the models.

Figure 3 Determination of the MA and Ne positions in the crystal structure of MAPbI3 at selected pressures. Projections of the relevant fragments of the structure onto the ac plane are in (a) and (c). Small dots indicate I atoms in the plane for which the difference electron density maps are shown in (b) and (d) with positive (red) and negative (blue) areas. (b) The maps were calculated using only Pb and I atoms. The maxima of the difference electron densities are identified with MA cations (dark-blue circles) and Ne atoms (cyan circles). The density varies: from −0.32 to 1.58 e Å^−3 for the released crystal at P = 1 atm; from 0.20 to 0.41 e Å^−3 for the pristine crystal at P = 1 atm; from −1.44 to 1.97 e Å^−3 for P = 0.69 GPa; from −1.13 to 1.86 e Å^−3 for P = 20.27 GPa. (d) The residual electron density maps were calculated using all atoms of the structure. The residual electron density varies: from −0.3 to 0.51 e Å^−3 atm for the released crystal at P = 1; from −0.27 to 0.23 e Å^−3 for the pristine crystal at P = 1 atm; from −1.06 to 1.07 e Å^−3 for P = 0.69 GPa; from −0.54 to 0.56 e Å^−3 for P = 20.27 GPa.

Refinement of all atomic parameters for MA and Ne helped to confirm or correct the space group selected previously for the framework at each pressure. A similar procedure for the structure determination was used for all applied pressures for both Ne and Ar as the PTM.

As expected, the inclusion of Ne and Ar in the structure has a varying effect on the symmetry and the bulk modulus at different pressures. The resulting structures made it possible to determine the interatomic distances, and consequently the nature and hierarchy of interactions between various components of each structure.

The basic crystallographic information for eight different pressures with Ne as the PTM and six different pressures with Ar as the PTM is provided in Tables 1 and 2, respectively, and is visualized in Fig. 4. Further details are listed in Tables S1 and S2. It should be noted that, despite the reflections-to-parameters ratio which is 5.6 and 4.1 for the Ne-containing crystal at 16.43 and 20.27 GPa, respectively, the criteria R, wR, S = 0.051, 0.057, 1.44 for 16.43 GPa and 0.043, 0.064, 1.49 for 20.27 GPa, and the residual electron density ρ_max, ρ_min = 0.58, −0.60 e Å⁻³ for 16.43 GPa and 1.06, −1.25 e Å⁻³ for 20.27 GPa (column VI and VII in Table S1) show that the corresponding structure solutions are correct. These structures obtained at the highest pressures are essential for understanding the Ne intercalation, which is also confirmed by the presence of Ne in the released crystal under ambient conditions.

Table 1
Crystallographic data and composition for Ne-MAPbI₃ in the 0–20 GPa pressure range

	NexMAPbI3	NexMAPbI3	NexMAPbI3	Ne0.97MAPbI3
P (GPa)	0.69 → 1.5 → 2.69	4.56 → 7.4	16.43 → 20.27	1 atm (released)
Crystal system	Trigonal	Orthorhombic	Tetragonal	Tetragonal
Space group		Im2m	I4/mmm	I422
a (Å)	17.3128 (9) → 17.0325 (9) → 16.7757 (9)	11.435 (3) → 11.196 (3)	10.700 (5) → 10.538 (5)	8.876 (1)
b (Å)	= a	11.437 (3) → 11.197 (3)	= a	= a
c (Å)	10.6019 (5) → 10.4338 (5) → 10.2267 (5)	11.442 (3) → 11.201 (3)	10.620 (10) → 10.3793 (11)	12.672 (1)
x in Nex	0.42 (1) → 0.60 (1) → 0.91 (1)	1.10 (1) → 1.41 (1)	2.17 (1) → 2.50 (1)	0.97

Table 2
Crystallographic data and composition for Ar-containing MAPbI₃ in the 0–2.4 GPa pressure range

	ArxMAPbI3	ArxMAPbI3
P (GPa)	0.18 → 0.49 → 0.98	1.34 → 2.10 → 2.39
Crystal system	Tetragonal	Orthorhombic
Space group	P42bc	Immm
a (Å)	8.850 (5) → 8.7468 (15) → 8.7222 (15)	12.1294 (12) → 12.0192 (10) →11.900 (11)
b (Å)	= a	12.1415 (12) → 12.0195 (10) → 11.990 (1)
c (Å)	12.520 (5) → 12.398 (10) → 11.9979 (15)	12.1734 (15) → 12.0213 (10) → 11.920 (1)
x in Arx	0.76 (1) → 1.00 (1) → 1.34 (1)	1.40 (1) → 1.78 (1) → 1.75 (1)

Figure 4 Evolution of crystallographic characteristics of MAPbI3 under pressure with (a) Ne and (b) Ar as the pressure transmitting media (PTM). Panels a(i) and b(i) show the symmetry transformation of the unit cell. Unit cells are shown in different colours for different crystallographic systems in relation to a primitive perovskite cube (green line). Panels a(ii), b(ii) show the pressure dependence of the unit-cell volume and crystal density. Points in the diagrams are coloured according to the unit cells in panels (i). Green and black points correspond to the pristine and released crystals, respectively.

3. Results and discussion

3.1. The high-pressure NeMAPbI₃ compounds

The crystal structure at room temperature (293 K) was determined for 0.69, 1.5, 2.69, 4.56, 7.4, 16.43 and 20.27 GPa pressures and for ambient pressure after decompression (Table 1). Above 4 GPa an amorphous phase appears, coexisting with the crystalline one. The amorphous contribution slowly grows upon further increase of pressure and completely disappears after pressure is released (Fig. S1).

The XRD data obtained at 0.11 GPa indicate the coexistence of two phases: a tetragonal phase, characteristic of ambient pressure, and a pseudo-cubic phase, which is typical for higher pressures (Fig. S3). This is consistent with the first-order phase transition, which was reported before between 0.3 GPa and 0.4 GPa (Capitani et al., 2016; Szafrański & Katrusiak, 2016; Francisco-López et al., 2018). However, for the pseudo-cubic phase, we found the space group , which differs from the cubic and orthorhombic Imm2 reported previously by Szafrański & Katrusiak (2016) and Capitani et al. (2016), respectively. We observed a second phase transformation between 2.69 GPa and 4.56 GPa. It is also in good agreement with the literature value of 2.5 GPa (Szafrański & Katrusiak, 2016) and 2.7 GPa (Francisco-López et al., 2018). Even so, in contrast to the reported space group (Szafrański & Katrusiak, 2016), only its orthorhombic subgroup, Im2m, was found to describe the symmetry of the phase above 4.56 GPa. Furthermore, for the first time we observed a third transformation, from the orthorhombic to a tetragonal phase (space group I4/mmm) between 7.4 GPa and 16.43 GPa. The unit cells and space groups corresponding to each phase are shown in Fig. 4(a)(i). We explain the difference in the symmetry, the presence of a third phase transition and the lack of amorphization up to 20 GPa by the intercalation of Ne, which we found for the high-pressure phases.

Fig. 5 illustrates the evolution of the NeMAPbI₃ structure under compression.

Figure 5 Schematic diagram of the NeMAPbI3 structure evolution under compression and after pressure release. Panel (a) indicates the arrangement of Ne atoms at the faces of the primitive perovskite cubic unit cell. These faces are represented by cyan squares formed by I atoms. Depending on pressure, some of the Ne sites can be empty or partially occupied. Panel (b) shows a pressure-induced change of the crystal composition. In the chemical formula, y and(1 − y) refer to MA at the long-range-ordered and the non-localized (non-periodic) positions, respectively. Panel (c) presents the shortest interatomic distances for Ne–I, Ne–MA and I–MA under different pressures. Panel (d) demonstrates the main trend of the pressure-induced structure evolution, that is of a gradual increase in the number and occupancy of Ne sites, indicated in (a). Unexpectedly, all these sites are also partially occupied in the released crystal.

First, we observe evolution of the compound composition [Fig. 5(b)]: (i) a gradual pressure-induced growth in the Ne content and (ii) a gradual disappearance of the MA cation from the detectable, i.e. periodic over a long range, positions.

The observation (i) concerns positions of Ne atoms and their corresponding site occupancies. The intercalated Ne atoms are located in large voids of the inorganic framework, more precisely at the faces of the primitive perovskite cube [Fig. 5(a)], with a gradual increase in the occupancy of these sites upon compression [Fig. 5(d) and Figs. S4a and S5 in the supporting information]. The four neighbouring I atoms surround each Ne atom. The average occupancy of Ne sites starts at approximately one-third in the low-pressure phases and goes up with pressure, eventually approaching one when Ne atoms sit at each face. At 20.27 GPa, Ne sites are fully occupied for the faces of only four out of six possible orientations, and the remaining two are half occupied. One can therefore expect that even higher pressure is required in order to achieve the full occupancy. The corresponding composition, Ne₃PbI₃(MA), reflects the maximum possible Ne content in the structure.

The observation (ii) needs some extended explanation. A reversible transformation, which restores all the long-range-ordered positions of MA in the released crystal at ambient pressure (Fig. 3), indicates that this cation can be in two different states in the high-pressure crystal: the long-range-ordered state (i.e. periodic) and the randomly distributed one (i.e. non-periodic). In order to emphasize these two states of MA, we use the Ne_xMA_yPbI₃(MA)_1–y designation for the chemical formula, where indices y and (1 − y) denote the relative quantities of the long-range-ordered and the randomly distributed MA, respectively. The presence of two states for the MA cation is a direct confirmation of the assumption that the long-range ordering of MA is violated under high pressure, proposed by Ou et al. (2016), Capitani et al. (2016) and Szafrański & Katrusiak (2016). According to this assumption, a lack of long-range ordering of MA leads to destruction of the inorganic (Pb,I)-framework, which is kept by the I–MA periodic interactions. Indeed, a decrease in the amount for long-range-ordered MA leads to a huge increase in the atomic displacement parameters for I atoms (Fig. 6), which is a sign of the destruction of the inorganic framework. Destruction of the inorganic framework leads to compound amorphization. However, we observed that with the Ne PTM, the periodic crystal structure still exists up to 20 GPa. The reasons of this can be understood from the analysis of the Ne–I, Ne–AM and I–MA interatomic distances found for the long-range-ordered MA cation [Fig. 5(c)]. The short distances MA—Ne of ∼1.9 Å indicating the corresponding interaction at P < 3 GPa can be recognized as unstable with respect to pressure, since the content of the long-range-ordered MA rapidly reduces from 0.5 (4.56 GPa) to 0.25 (7.4 GPa) per chemical formula, and the long-range-ordered MA is no longer observed for P ≥ 16.3 GPa. If the expected rapid amorphization does not appear, it means that stabilization of the (Pb,I)-framework is kept by another stabilizer, which is different from MA; it is Ne atoms in the considered case. Indeed, for P > 4 GPa, the loss of the long-range order for more than 50% of MA switches the shortest interatomic distance (i.e. the strongest interaction of Ne) from Ne—MA to Ne—I [Fig. 5(c)]. Consequently, the Ne—I interactions can be considered as the cause of stabilization of the framework, preventing the amorphization.

Figure 6 Pressure-dependent atomic displacement parameters (ADP) of I atoms for the representative fragment of the inorganic framework. Panel (a) shows the fragment under three pressures with the long-range-ordered MA cation. Panel (b) shows the fragment under two pressures with the partially long-range ordered MA cation. Panel (c) presents the fragment corresponding to the absence of the long-range-ordered MA cation. The ADP ellipsoids are shown with 50% probability for each pressure.

The stabilizing role of Ne under high pressure is also confirmed by the distortions observed in the (Pb,I)-framework: the minimal distortions (the I—Pb—I angle ≃ 88.4–90.3° instead of the ideal 90° and the Pb—I—Pb angle ≃ 178–180° instead of the ideal 180°) were found in tetragonal structures at the highest pressure, when the long-range order MA is lost and the content of Ne is maximal (Table S3).

Thus, the progressive intercalation of Ne is the general trend in the pressure evolution of the NeMAPbI₃. The phenomenon is driven by the Ne—I interaction, which is substantially enhanced above 4 GPa.

Surprisingly, the occupation of Ne sites in all directions is preserved in the released structure under ambient pressure, but with a much smaller probability of approximately one-third [Fig. 5(d)]. The mean Ne–MA and Ne–I distances in the released structure, 2.83 Å and 2.78 Å, respectively, are very similar [Fig. 5(c)]. The minimum Ne–MA distance of approximately 2.3 Å in the released crystal can be responsible for this stabilization. However, this is the distance between the partially occupied Ne and MA sites, so it is problematic to say with certainty whether such separation is indeed realized.

In the 0–20 GPa pressure range the bulk modulus B₀, calculated using the Birch−Murnaghan model (Birch, 1947), varies from 5.3 GPa at the lowest to 10.6 GPa at the highest pressure. These numbers fall within the spread of values in the literature (Capitani et al., 2016; Jaffe et al., 2016) even for the crystalline phase at 20 GPa, which was absent for other PTMs.

3.2. The high-pressure ArMAPbI₃ compounds

The structure was determined at pressures of 0.18, 0.49, 0.98, 1.34, 2.1, and 2.39 GPa at room temperature (Table 2). Above 1.34 GPa an amorphous phase appears, coexisting with the crystalline one. The amorphous contribution grows rapidly with increasing pressure until no crystalline phase can be observed above 3.6 GPa (Fig. S2). This amorphization is irreversible in our experiments.

The tetragonal unit-cell parameters, characteristic for the ambient conditions, have been identified in the ArMAPbI₃ structure up to 1 GPa [Table 2 and Fig. 4(b)(i)]. The space group P4₂bc, which is new for the title compound, turned out to be the best fit in the 0.18–0.98 GPa pressure range. Only one transformation of this unit cell was detected for ArMAPbI₃, happening between 1 GPa and 1.3 GPa. The pseudo-cubic orthorhombic unit cell [Fig. 4(b)(i)] and the Immm space group are characteristic for the lattice for P > 1 GPa (Table 2). No distortion in the long-range order was detected for the MA cation. In comparison to NeMAPbI₃, growth in the Ar content as a function of pressure is 5.5 times larger, reaching the composition Ar_1.4MAPbI₃ at 1.34 GPa. In the case of Ne PTM, the nearly equivalent composition, Ne_1.41MA_0.25­PbI₃(MA)_0.75, occurs at 7.4 GPa (Tables 1 and 2). This indicates a much stronger interaction of MAPbI₃ with Ar than with Ne.

The pressure-induced structural evolution of ArMAPbI₃ (Fig. 7) is associated with a gradual growth in the Ar content [Fig. 7(b)], accompanied by the contraction of the Ar–I and Ar–MA distances [Fig. 7(c)]. For P < 1 GPa, the MA cations, Ar and I atoms closest to each other are arranged into chains, which polymerize in two dimensions upon further compression [Fig. 7(d)]. Influence of the lattice contraction on the chain geometry is illustrated in Fig. 8.

Figure 7 Sketch of the ArMAPbI3 structure evolution under compression. Panel (a) schematically shows a plane (pinkish grey square) where the Ar atoms are located. The plane is defined by I atoms and the centre of the MA cation. Panel (b) shows the pressure-induced change of the crystal composition. Panel (c) presents the shortest interatomic distances for Ar–I, Ar–MA and I–MA under different pressures. Panel (d) demonstrates the main trend of the pressure-induced structure evolution: below 1 GPa, Ar, MA and I atoms are arranged in chains, along the shortest Ar–I and Ar–MA distances, shown in (c); under increasing pressure, the number of the Ar positions rises, and the crossing chains form a layer. Each pinkish grey rectangle corresponds to the one shown in (a). Pinkish grey-coloured segments indicate the occupancies of the Ar sites.

Figure 8 Pressure-induced transformation of the tetragonal ArMAPbI3 phase. (a) Position of the I–Ar–MA–Ar– group within the (Pb,I)-framework. (b) Deformation of the group configuration and its connection to I atoms. Pink-coloured segments indicate the occupancies of the Ar sites. The MA–Ar and Ar–I interatomic distances are given in Å.

The shortest interatomic distances of ∼2 Å found for Ar–I and Ar–N (MA) at 2.1 and 2.39 GPa can be considered as a reasonable approximation if two arguments are taken into account. First, the value of 1.84 Å was theoretically predicted for the Ar–N separation for ambient pressure (Novak & Fortenberry, 2016). Second, large and prolate ADP ellipsoids of the I atoms imply an anharmonic character of the atomic displacements, which indicates that the actual Ar–I distances are longer.

Nevertheless, we consider the dramatic reduction of the minimum Ar–MA and Ar–I distances at P ≥ 2 GPa [circled by red line in Fig. 7(c)] as a trigger for the complete and irreversible structure amorphization. In fact, we recorded a crystalline state at the time of its destruction.

Thus, the pressure-induced formation of the stable I–Ar–MA–Ar– chains and their polymerization [Fig. 7(d)] is at the origin of the structural evolution and amorphization of ArMAPbI₃.

Detailed characteristics of the progressive changes in the ArMAPbI₃ structure under pressure are also given in the supporting information (Figs. S4b, S6 and S7).

3.3. Different impact of Ne and Ar as a pressure transmitting medium

The present results show that both Ne and Ar interact with MAPbI₃, but in different ways. Interactions between Ne and I atoms stabilize the inorganic (Pb,I)-framework up to 20 GPa and suppress amorphization of the crystal, despite the vanishing of the long-range ordering of MA. Ne serves as a structural stabilizer instead of MA for pressures higher than 4 GPa. Unlike Ne, Ar interacts with both I and MA even under low pressure of 0.18 GPa. These interactions accelerate the irreversible amorphization, which starts at P > 2 GPa. The difference between the influences of Ne and Ar is clearly related to the difference in their chemical activities, which are defined by their electronic configurations, i.e. their atomic radii being 0.38 Å for Ne and 0.71 Å for Ar.

The photo-luminescence (PL) microscopy images and steady-state PL spectra acquired under ambient pressure revealed that the PL properties were strongly dependent on the type of PTM and on the maximum pressure attained. Using the dual wavelength excitation technique (Mor et al., 2016) these observations, described in detail in Section S6, point to a markedly higher degree of amorphization for MAPbI₃ single crystals exposed to high pressure in Ar than in Ne. Thus, the optical characterization of MAPbI₃ supports the conclusions of the X-ray study that the large difference in the atomic radii of Ar and Ne leads to significantly different effects of high pressure on the crystallinity of MAPbI₃ after pressure release.

3.4. Influence of Ne and Ar on the methylammonium cation mobility

The role of the mobility of the MA cation is often discussed (Motta et al., 2015; Ou et al., 2016; Capitani et al., 2016; Szafrański & Katrusiak, 2016). The high-pressure amorphization is also directly linked to this phenomenon. According to Ou et al. (2016), Capitani et al. (2016) and Szafrański & Katrusiak (2016), the strong pressure-induced interaction between the MA cations and I atoms leads to the absence of the MA periodicity, which was considered as a template for the stability of the (Pb,I)-framework. Following this interpretation, our results support the following scenarios of the influence of Ne and Ar on the MA cation behaviour. In both cases, Ne–MA and Ar–MA interactions minimize the MA mobility by fixing the position of the MA dumbbell (the log-range-ordered form of MA). In particular, this explains the absence of cubic symmetry for the high-pressure phases.

In the case of Ne–PTM, up to ∼3 GPa, MA interacts with both Ne and I; that stabilizes its long-range ordering. For P > 3 GPa, intensifying interaction between MA and 12 neighbouring I atoms forces this cation to lose its long-range periodicity, first partially (for 3 GPa < P < 8 GPa) then completely (for P > 8 GPa). However, the Ne–I interaction becomes sufficiently strong to stabilize the (Pb,I)-framework. This prevents amorphization and maintains the crystalline state up to 20.27 GPa. These pressure-induced Ne–I interactions remain after decompression.

In the case of Ar PTM, MA cations interact with Ar to form –I–Ar–MA–Ar– chains as Ar enters the crystal. Formation of the chains prevents strong interaction between MA and I and, consequently, stabilizes the long-range periodicity of MA. At 1.34 GPa, some of the cations still exist outside of the chains. The uncovered cations stimulate additional absorption of Ar by the crystal, and all MA cations are involved in the polymerized chains at 2.39 GPa, but some of the Ar–MA and Ar–I distances are too short. On the one hand, it points to strong MA–Ar interactions, which benefit from the competition with the MA–I ones. On the other hand, the I–Ar–MA–Ar– chains get crowded in the restricted space between the PbI₆ octahedra and they crush the structure. This means collapse of the structure. Despite somewhat speculative character, this scenario can explain both the small observed contribution of the crystalline phase at 2.39 GPa and the rapid irreversible amorphization upon further pressure increase.

4. Conclusions

Using single-crystal synchrotron diffraction data, the crystal structure of CH₃NH₃PbI₃ (MAPbI₃) was studied under different pressures with noble gases, Ne and Ar, as pressure transmitting media creating hydro­static conditions. The following main conclusions have been drawn from the study.

(i) In the case of MAPbI₃ compression up to 20.3 GPa, the noble gas atoms of the pressure transmitting media are not inert, but rather they form NeMAPbI₃ and ArMAPbI₃ high-pressure-induced compounds.

(ii) Ne mainly interacts with I atoms, preventing amorphization and stabilizing the high-pressure crystalline state up to 20.27 GPa, despite the migration of MA cations to non-periodic positions. This means a loss of the long-range ordering of MA within the crystal lattice. The high-pressure transformation is reversible and the Ne_0.97MAPbI₃ compound is stable at ambient conditions after decompression.

(iii) Ar interacts with both MA and I, thus forming chains and driving their pressure-induced polymerization up to P = 2.39 GPa. Compression of the (Pb, I)-framework destroys the polymerized structure and, consequently, the framework itself, initiating the irreversible and rapid amorphization of the compound.

(iv) The difference between the pressure-induced impacts of Ne and Ar is related to the difference in their atomic radii and, consequently, their propensity towards interatomic interactions in the restricted space between the PbI₆ octahedra.

We believe that the findings presented can encourage the research community to conduct deeper experimental and theoretical studies of plausible chemical reactions of noble gases in the interstitial compartments of other compounds under high pressure.

5. Related literature

References cited in the supporting information include: Bruce et al. (2011), Derenzo et al. (2013), Innocenzo et al. (2014), Klintenberg et al. (2003) and Wright et al. (2016).

Supporting information

Computing details

neon methylammonium lead iodide (I)

Crystal data

CH6I3NNe0.424Pb	F(000) = 3099
Mr = 628.5	Dx = 4.551 Mg m^−3
Trigonal, R3	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: -R 3	Cell parameters from 1677 reflections
a = 17.3128 (9) Å	θ = 2.8–12.8°
c = 10.6019 (9) Å	µ = 5.25 mm^−1
V = 2752.0 (4) Å^3	T = 293 K
Z = 12	Irregular

Data collection

Abstract diffractometer	392 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.055
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 12.8°, θmin = 2.8°
	h = −20→20
1677 measured reflections	k = −14→16
799 independent reflections	l = −11→12

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.070	8 constraints
wR(F^2) = 0.078	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 1.69	(Δ/σ)max = 0.048
799 reflections	Δρmax = 1.87 e Å^−3
44 parameters	Δρmin = −1.68 e Å^−3

Special details

Experimental. High pressure P = 0.69 GPa. Ne-PTM.

Refinement. No H atoms are included into the model; Twined structure. C, N and Ne atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	0	0.0476 (8)
Pb2	0	0	0	0.0495 (9)
I1	0.3105 (2)	0.4087 (3)	0.1193 (4)	0.117 (3)
I2	0.0477 (3)	0.1643 (3)	0.1698 (5)	0.117 (3)
N1	−0.148 (3)	0.206 (2)	0.201 (4)	0.095 (10)*	0.5
C1	−0.148 (3)	0.206 (2)	0.201 (4)	0.095 (10)*	0.5
Ne1	0.416 (4)	−0.156 (3)	0.358 (5)	0.019 (12)*	0.1583
N2	0.036 (4)	0.029 (4)	0.442 (6)	0.031 (16)*	0.1667
C2	0.036 (4)	0.029 (4)	0.442 (6)	0.031 (16)*	0.1667
Ne2	0.359 (7)	−0.074 (8)	0.617 (10)	0.06 (2)*	0.124

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0515 (10)	0.0510 (11)	0.0382 (8)	0.0241 (9)	−0.0013 (6)	0.0001 (7)
Pb2	0.0547 (11)	0.0547 (11)	0.0391 (13)	0.0273 (6)	0	0
I1	0.068 (2)	0.171 (5)	0.076 (2)	0.034 (3)	0.0446 (19)	0.023 (2)
I2	0.125 (4)	0.089 (3)	0.128 (3)	0.046 (3)	−0.035 (3)	−0.072 (3)

Geometric parameters (Å, º)

Pb1—I1^i	3.131 (4)	I1—Ne2^ix	2.81 (17)
Pb1—I1^ii	3.111 (7)	I2—Ne1^x	2.60 (6)
Pb1—I1^iii	3.131 (4)	I2—Ne2^xi	2.98 (12)
Pb1—I1^iv	3.111 (7)	N1—C1^xii	1.38 (5)
Pb1—I2^i	3.128 (5)	N1—Ne1^xiii	2.79 (9)
Pb1—I2^iii	3.128 (5)	N1—Ne1^x	2.94 (10)
Pb2—I2	3.108 (6)	N1—Ne2^xiii	1.76 (11)
Pb2—I2^v	3.108 (5)	N1—Ne2^x	3.14 (11)
Pb2—I2^vi	3.108 (8)	Ne1—C2^xiv	3.18 (10)
Pb2—I2^vii	3.108 (6)	Ne1—C2^xv	2.55 (7)
Pb2—I2^iv	3.108 (5)	N2—C2^xvi	1.35 (10)
Pb2—I2^viii	3.108 (8)	N2—C2^xvii	1.35 (10)
I1—Ne1^iii	2.61 (7)
I1^i—Pb1—I1^ii	90.37 (13)	Ne1^xiii—C1—Ne1^x	152 (2)
I1^i—Pb1—I1^iii	180.0 (5)	Ne1^xiii—C1—Ne2^xiii	96 (6)
I1^i—Pb1—I1^iv	89.63 (13)	Ne1^xiii—C1—Ne2^x	83 (3)
I1^i—Pb1—I2^i	90.14 (12)	Ne1^x—C1—Ne2^xiii	112 (6)
I1^i—Pb1—I2^iii	89.86 (12)	Ne1^x—C1—Ne2^x	69 (3)
I1^ii—Pb1—I1^iii	89.63 (13)	Ne2^xiii—C1—Ne2^x	179 (5)
I1^ii—Pb1—I1^iv	180.0 (5)	I1^iii—Ne1—I2^xiv	171.8 (19)
I1^ii—Pb1—I2^i	89.47 (15)	I1^iii—Ne1—C1^xx	88 (2)
I1^ii—Pb1—I2^iii	90.53 (15)	I1^iii—Ne1—C1^xiv	86.9 (19)
I1^iii—Pb1—I1^iv	90.37 (13)	I1^iii—Ne1—C2^xiv	106 (2)
I1^iii—Pb1—I2^i	89.86 (12)	I1^iii—Ne1—C2^xv	92 (3)
I1^iii—Pb1—I2^iii	90.14 (12)	I2^xiv—Ne1—C1^xx	89.0 (19)
I1^iv—Pb1—I2^i	90.53 (15)	I2^xiv—Ne1—C1^xiv	86.7 (18)
I1^iv—Pb1—I2^iii	89.47 (15)	I2^xiv—Ne1—C2^xiv	78 (2)
I2^i—Pb1—I2^iii	180.0 (5)	I2^xiv—Ne1—C2^xv	93 (3)
I2—Pb2—I2^v	89.82 (16)	N1^xx—Ne1—C2^xiv	164 (3)
I2—Pb2—I2^vi	89.82 (16)	N1^xx—Ne1—C2^xv	167 (3)
I2—Pb2—I2^vii	180.0 (5)	N1^xiv—Ne1—C2^xiv	156 (3)
I2—Pb2—I2^iv	90.18 (16)	N1^xiv—Ne1—C2^xv	165 (3)
I2—Pb2—I2^viii	90.18 (16)	C1^xx—Ne1—C2^xiv	164 (3)
I2^v—Pb2—I2^vi	89.82 (17)	C1^xx—Ne1—C2^xv	167 (3)
I2^v—Pb2—I2^vii	90.18 (16)	C1^xiv—Ne1—C2^xiv	156 (3)
I2^v—Pb2—I2^iv	180.0 (5)	C1^xiv—Ne1—C2^xv	165 (3)
I2^v—Pb2—I2^viii	90.18 (17)	Ne1^ix—N2—Ne1^x	106 (3)
I2^vi—Pb2—I2^vii	90.18 (16)	Ne1^ix—N2—C2^v	145 (6)
I2^vi—Pb2—I2^iv	90.18 (17)	Ne1^ix—N2—C2^vi	121 (8)
I2^vi—Pb2—I2^viii	180.0 (5)	Ne1^ix—N2—C2^xxi	159 (5)
I2^vii—Pb2—I2^iv	89.82 (16)	Ne1^ix—N2—C2^xvi	124 (5)
I2^vii—Pb2—I2^viii	89.82 (16)	Ne1^ix—N2—C2^xvii	141 (4)
I2^iv—Pb2—I2^viii	89.82 (17)	Ne1^x—N2—C2^vi	95 (7)
Pb1^xviii—I1—Pb1^xix	157.44 (14)	Ne1^x—N2—C2^xxi	94 (4)
Ne1^x—I2—Ne2^xi	113 (3)	Ne1^x—N2—C2^xvi	129 (5)
C1^xii—N1—Ne1^xiii	82 (3)	Ne1^x—N2—C2^xvii	92 (6)
C1^xii—N1—Ne1^x	70 (3)	I1^xv—Ne2—I2^xxii	135 (4)
C1^xii—N1—Ne2^xiii	178 (5)	I1^xv—Ne2—C1^xx	115 (6)
N1^xii—C1—Ne1^xiii	82 (3)	I1^xv—Ne2—C1^xiv	115 (4)
N1^xii—C1—Ne1^x	70 (3)	I2^xxii—Ne2—C1^xx	108 (6)
N1^xii—C1—Ne2^xiii	178 (5)	I2^xxii—Ne2—C1^xiv	109 (4)

Symmetry codes: (i) x+1/3, y−1/3, z−1/3; (ii) −y+1, x−y, z; (iii) −x+2/3, −y+1/3, −z+1/3; (iv) y, −x+y, −z; (v) −y, x−y, z; (vi) −x+y, −x, z; (vii) −x, −y, −z; (viii) x−y, x, −z; (ix) y+1/3, −x+y+2/3, −z+2/3; (x) x−y−2/3, x−1/3, −z+2/3; (xi) x−1/3, y+1/3, z−2/3; (xii) −x−1/3, −y+1/3, −z+1/3; (xiii) −x+y+1/3, −x+2/3, z−1/3; (xiv) y+1/3, −x+y−1/3, −z+2/3; (xv) x−y+1/3, x−1/3, −z+2/3; (xvi) y, −x+y, −z+1; (xvii) x−y, x, −z+1; (xviii) x−1/3, y+1/3, z+1/3; (xix) −x+y+1, −x+1, z; (xx) −y+2/3, x−y+1/3, z+1/3; (xxi) −x, −y, −z+1; (xxii) x+1/3, y−1/3, z+2/3.

neon methylammonium lead iodide (II)

Crystal data

CH6I3NNe0.601Pb	F(000) = 3120
Mr = 632.1	Dx = 4.805 Mg m^−3
Trigonal, R3	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: -R 3	Cell parameters from 1449 reflections
a = 17.0325 (9) Å	θ = 2.8–12.8°
c = 10.4338 (5) Å	µ = 13.41 mm^−1
V = 2621.4 (4) Å^3	T = 293 K
Z = 12	Irregular

Data collection

Abstract diffractometer	427 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.048
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 12.8°, θmin = 2.8°
	h = −16→12
1449 measured reflections	k = −20→20
673 independent reflections	l = −9→11

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.049	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.059	(Δ/σ)max = 0.048
S = 1.73	Δρmax = 1.00 e Å^−3
673 reflections	Δρmin = −0.89 e Å^−3
40 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
1 restraint	Extinction coefficient: 140.2 (10)

Special details

Experimental. High pressure P = 1.5 GPa. Ne-PTM.

Refinement. No H atoms are included into the model; Twined structure. C, N and Ne atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	0	0.0490 (6)
Pb2	0	0	0	0.0502 (8)
I1	0.30622 (18)	0.4074 (3)	0.1121 (3)	0.1047 (19)
I2	0.0411 (2)	0.1639 (3)	0.1723 (5)	0.1023 (18)
N1	−0.1481 (18)	0.2047 (16)	0.202 (3)	0.074 (6)*	0.5
C1	−0.1481 (18)	0.2047 (16)	0.202 (3)	0.074 (6)*	0.5
N2	0.05 (5)	−0.04 (5)	0.47 (4)	0.3932*	0.1667
C2	0.05 (5)	−0.04 (5)	0.47 (4)	0.3932*	0.1667
Ne1	0.362 (5)	−0.074 (5)	0.654 (8)	0.23 (3)*	0.4005

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0480 (8)	0.0474 (8)	0.0512 (8)	0.0236 (7)	−0.0002 (5)	0.0013 (5)
Pb2	0.0489 (9)	0.0489 (9)	0.0529 (16)	0.0244 (4)	0	0
I1	0.0533 (15)	0.149 (3)	0.083 (2)	0.0293 (19)	0.0301 (14)	0.0158 (18)
I2	0.086 (2)	0.0826 (19)	0.134 (3)	0.0391 (17)	−0.0327 (19)	−0.070 (2)

Geometric parameters (Å, º)

Pb1—I1^i	3.094 (3)	Pb2—I2^iv	3.092 (4)
Pb1—I1^ii	3.089 (6)	Pb2—I2^viii	3.092 (6)
Pb1—I1^iii	3.094 (3)	I1—N2^ix	3.1 (12)
Pb1—I1^iv	3.089 (6)	I1—Ne1^ix	2.90 (11)
Pb1—I2^i	3.091 (4)	I2—Ne1^x	2.60 (9)
Pb1—I2^iii	3.091 (4)	N1—C1^xi	1.34 (4)
Pb2—I2	3.092 (5)	C1—Ne1^xii	1.92 (8)
Pb2—I2^v	3.092 (4)	N2—C2^xiii	1.5 (9)
Pb2—I2^vi	3.092 (6)	N2—C2^xiv	1.5 (10)
Pb2—I2^vii	3.092 (5)
I1^i—Pb1—I1^ii	90.43 (11)	I2^vi—Pb2—I2^viii	180.0 (5)
I1^i—Pb1—I1^iii	180.0 (5)	I2^vii—Pb2—I2^iv	89.61 (12)
I1^i—Pb1—I1^iv	89.57 (11)	I2^vii—Pb2—I2^viii	89.61 (12)
I1^i—Pb1—I2^i	90.40 (10)	I2^iv—Pb2—I2^viii	89.61 (13)
I1^i—Pb1—I2^iii	89.60 (10)	Pb1^xv—I1—Pb1^xvi	153.84 (12)
I1^ii—Pb1—I1^iii	89.57 (11)	Pb1^xv—I1—N2^ix	76 (10)
I1^ii—Pb1—I1^iv	180.0 (5)	Pb1^xv—I1—Ne1^ix	95.0 (15)
I1^ii—Pb1—I2^i	89.60 (12)	Pb1^xvi—I1—N2^ix	102 (13)
I1^ii—Pb1—I2^iii	90.40 (12)	Pb1^xvi—I1—Ne1^ix	93.7 (15)
I1^iii—Pb1—I1^iv	90.43 (11)	N2^ix—I1—Ne1^ix	161 (14)
I1^iii—Pb1—I2^i	89.60 (10)	Pb1^xv—I2—Pb2	153.83 (16)
I1^iii—Pb1—I2^iii	90.40 (10)	Pb1^xv—I2—Ne1^x	93.1 (15)
I1^iv—Pb1—I2^i	90.40 (12)	Pb2—I2—Ne1^x	94.6 (18)
I1^iv—Pb1—I2^iii	89.60 (12)	C1^xi—N1—Ne1^xii	173 (3)
I2^i—Pb1—I2^iii	180.0 (5)	N1^xi—C1—Ne1^xii	173 (3)
I2—Pb2—I2^v	89.61 (12)	I1^xvii—N2—C2^v	120 (30)
I2—Pb2—I2^vi	89.61 (12)	I1^xvii—N2—C2^vi	163 (19)
I2—Pb2—I2^vii	180.0 (5)	I1^xvii—N2—C2^xviii	138 (20)
I2—Pb2—I2^iv	90.39 (12)	I1^xvii—N2—C2^xiii	130 (50)
I2—Pb2—I2^viii	90.39 (12)	I1^xvii—C2—N2^v	120 (30)
I2^v—Pb2—I2^vi	89.61 (13)	I1^xvii—C2—N2^vi	163 (19)
I2^v—Pb2—I2^vii	90.39 (12)	I1^xvii—C2—N2^xviii	138 (20)
I2^v—Pb2—I2^iv	180.0 (5)	I1^xvii—C2—N2^xiii	130 (50)
I2^v—Pb2—I2^viii	90.39 (13)	I1^xvii—Ne1—I2^xix	139 (3)
I2^vi—Pb2—I2^vii	90.39 (12)	I1^xvii—Ne1—C1^xx	104 (4)
I2^vi—Pb2—I2^iv	90.39 (13)	I2^xix—Ne1—C1^xx	117 (4)

Symmetry codes: (i) x+1/3, y−1/3, z−1/3; (ii) −y+1, x−y, z; (iii) −x+2/3, −y+1/3, −z+1/3; (iv) y, −x+y, −z; (v) −y, x−y, z; (vi) −x+y, −x, z; (vii) −x, −y, −z; (viii) x−y, x, −z; (ix) y+1/3, −x+y+2/3, −z+2/3; (x) x−1/3, y+1/3, z−2/3; (xi) −x−1/3, −y+1/3, −z+1/3; (xii) −x+y+1/3, −x+2/3, z−1/3; (xiii) y, −x+y, −z+1; (xiv) x−y, x, −z+1; (xv) x−1/3, y+1/3, z+1/3; (xvi) −x+y+1, −x+1, z; (xvii) x−y+1/3, x−1/3, −z+2/3; (xviii) −x, −y, −z+1; (xix) x+1/3, y−1/3, z+2/3; (xx) −y+2/3, x−y+1/3, z+1/3.

neon methylammonium lead iodide (III)

Crystal data

CH6I3NNe0.91Pb	F(000) = 3157
Mr = 638.3	Dx = 5.103 Mg m^−3
Trigonal, R3	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: -R 3	Cell parameters from 703 reflections
a = 16.7757 (9) Å	θ = 2.9–13.7°
c = 10.2267 (5) Å	µ = 5.63 mm^−1
V = 2492.5 (3) Å^3	T = 293 K
Z = 12	Irregular

Data collection

Abstract diffractometer	239 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.090
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.7°, θmin = 2.9°
	h = −18→19
703 measured reflections	k = −20→18
387 independent reflections	l = −9→10

Refinement

Refinement on F	2 restraints
R[F^2 > 2σ(F^2)] = 0.084	0 constraints
wR(F^2) = 0.083	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 2.27	(Δ/σ)max = 0.050
387 reflections	Δρmax = 2.31 e Å^−3
40 parameters	Δρmin = −1.20 e Å^−3

Special details

Experimental. High pressure P=2.69 GPa. Ne-PTM.

Refinement. No H atoms are included into the model. C, N and Ne atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	0	0.078 (3)
Pb2	0	0	0	0.080 (6)
I1	0.3056 (5)	0.4070 (9)	0.1119 (12)	0.162 (8)
I2	0.0436 (8)	0.1664 (9)	0.1765 (18)	0.155 (7)
N1	−0.147 (5)	0.204 (3)	0.209 (6)	0.047 (17)*	0.5
C1	−0.147 (5)	0.204 (3)	0.209 (6)	0.047 (17)*	0.5
N2	0.044 (12)	0.005 (17)	0.434 (6)	0.07 (9)*	0.1667
C2	0.044 (12)	0.005 (17)	0.434 (6)	0.07 (9)*	0.1667
Ne1	0.983 (3)	0.732 (6)	0.014 (7)	0.15 (3)*	0.607 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.084 (4)	0.071 (4)	0.084 (7)	0.042 (3)	0.001 (4)	0.001 (5)
Pb2	0.090 (5)	0.090 (5)	0.060 (15)	0.045 (2)	0	0
I1	0.102 (6)	0.206 (11)	0.138 (14)	0.047 (9)	0.036 (6)	0.008 (12)
I2	0.147 (8)	0.130 (6)	0.163 (14)	0.051 (7)	−0.029 (10)	−0.101 (8)

Geometric parameters (Å, º)

Pb1—I1^i	3.035 (10)	Pb2—I2^viii	3.09 (2)
Pb1—I1^ii	3.048 (19)	I1—Ne1^ii	2.56 (12)
Pb1—I1^iii	3.035 (10)	I2—N2^v	3.23 (19)
Pb1—I1^iv	3.048 (19)	I2—Ne1^ix	2.77 (10)
Pb1—I2^i	2.983 (14)	N1—C1^x	1.39 (7)
Pb1—I2^iii	2.983 (14)	C1—Ne1^xi	1.99 (8)
Pb2—I2	3.090 (16)	N2—C2^v	1.2 (5)
Pb2—I2^v	3.090 (14)	N2—C2^vi	1.2 (3)
Pb2—I2^vi	3.09 (2)	N2—C2^xii	1.9 (2)
Pb2—I2^vii	3.090 (16)	N2—C2^xiii	1.51 (16)
Pb2—I2^iv	3.090 (14)	N2—C2^xiv	1.5 (2)
I1^i—Pb1—I1^ii	90.2 (4)	I2^vi—Pb2—I2^vii	90.7 (4)
I1^i—Pb1—I1^iii	180.0 (5)	I2^vi—Pb2—I2^iv	90.7 (5)
I1^i—Pb1—I1^iv	89.8 (4)	I2^vi—Pb2—I2^viii	180.0 (5)
I1^i—Pb1—I2^i	90.7 (4)	I2^vii—Pb2—I2^iv	89.3 (4)
I1^i—Pb1—I2^iii	89.3 (4)	I2^vii—Pb2—I2^viii	89.3 (4)
I1^ii—Pb1—I1^iii	89.8 (4)	I2^iv—Pb2—I2^viii	89.3 (5)
I1^ii—Pb1—I1^iv	180.0 (5)	Pb1^xv—I1—Pb1^xvi	153.6 (4)
I1^ii—Pb1—I2^i	89.2 (4)	Pb1^xv—I1—Ne1^ii	97.6 (18)
I1^ii—Pb1—I2^iii	90.8 (4)	Pb1^xvi—I1—Ne1^ii	92 (2)
I1^iii—Pb1—I1^iv	90.2 (4)	Pb1^xv—I2—Pb2	154.5 (5)
I1^iii—Pb1—I2^i	89.3 (4)	Pb1^xv—I2—N2^v	91 (4)
I1^iii—Pb1—I2^iii	90.7 (4)	Pb1^xv—I2—Ne1^ix	92.7 (17)
I1^iv—Pb1—I2^i	90.8 (4)	Pb2—I2—N2^v	91 (5)
I1^iv—Pb1—I2^iii	89.2 (4)	Pb2—I2—Ne1^ix	96 (2)
I2^i—Pb1—I2^iii	180.0 (5)	N2^v—I2—Ne1^ix	156 (6)
I2—Pb2—I2^v	89.3 (4)	C1^x—N1—Ne1^xi	175 (6)
I2—Pb2—I2^vi	89.3 (4)	I2^vi—N2—C2^v	125 (6)
I2—Pb2—I2^vii	180.0 (5)	I2^vi—N2—C2^vi	108 (11)
I2—Pb2—I2^iv	90.7 (4)	I2^vi—N2—C2^xii	159 (9)
I2—Pb2—I2^viii	90.7 (4)	I2^vi—N2—C2^xiii	140 (20)
I2^v—Pb2—I2^vi	89.3 (5)	I2^vi—N2—C2^xiv	162 (15)
I2^v—Pb2—I2^vii	90.7 (4)	I1^xvi—Ne1—I2^ix	144 (2)
I2^v—Pb2—I2^iv	180.0 (5)	I1^xvi—Ne1—C1^xvii	112 (4)
I2^v—Pb2—I2^viii	90.7 (5)	I2^ix—Ne1—C1^xvii	103 (4)

Symmetry codes: (i) x+1/3, y−1/3, z−1/3; (ii) −y+1, x−y, z; (iii) −x+2/3, −y+1/3, −z+1/3; (iv) y, −x+y, −z; (v) −y, x−y, z; (vi) −x+y, −x, z; (vii) −x, −y, −z; (viii) x−y, x, −z; (ix) −x+1, −y+1, −z; (x) −x−1/3, −y+1/3, −z+1/3; (xi) x−y−1/3, x−2/3, −z+1/3; (xii) −x, −y, −z+1; (xiii) y, −x+y, −z+1; (xiv) x−y, x, −z+1; (xv) x−1/3, y+1/3, z+1/3; (xvi) −x+y+1, −x+1, z; (xvii) y+2/3, −x+y+1/3, −z+1/3.

neon methylammonium lead iodide (IV)

Crystal data

CH6I3NNe1.098Pb	F(000) = 2069
Mr = 642.13	Dx = 5.701 Mg m^−3
Orthorhombic, Im2m	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: I -2 -2	Cell parameters from 780 reflections
a = 11.435 (3) Å	θ = 2.7–10.7°
b = 11.437 (3) Å	µ = 15.66 mm^−1
c = 11.442 (3) Å	T = 293 K
V = 1496.4 (7) Å^3	Irregular
Z = 8

Data collection

Abstract diffractometer	269 reflections with I > 2σ(I)
Radiation source: synchrotron	Rint = 0.119
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 10.7°, θmin = 2.7°
	h = −6→7
783 measured reflections	k = −10→11
783 independent reflections	l = −10→11

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.058	Weighting scheme based on measured s.u.'s w = 1/(σ^2(I) + 0.0016I^2)
wR(F^2) = 0.073	(Δ/σ)max = 0.041
S = 0.88	Δρmax = 0.40 e Å^−3
783 reflections	Δρmin = −0.42 e Å^−3
59 parameters	Absolute structure: 310 of Friedel pairs used in the refinement
2 restraints	Absolute structure parameter: 0.26 (8)

Special details

Experimental. High pressure P = 4.56 GPa. Ne-PTM.

Refinement. No H atoms are included into the model,Twined structure. A half of the CH3NH3 content is in the randomly distributed and non-detectable positions. C, N and Ne atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.7587 (12)	0.75	0.7371 (15)	0.501 (12)
I1	0.225 (3)	0.801 (3)	0	0.43 (2)
I2	0.769 (4)	0.205 (6)	0	0.74 (8)
I3	0	0.7464 (19)	0.797 (3)	0.425 (15)
I4	0	0.2255 (19)	0.694 (3)	0.415 (19)
I5	0.7406 (9)	0.0043 (10)	0.7368 (12)	0.326 (9)
Ne1	0	0.809 (4)	0.593 (5)	0.087 (14)*	0.5
Ne2	0.748 (5)	−0.001 (7)	0	0.20 (2)*	0.6965
Ne3	0.2439 (18)	0.0469 (18)	0.5	0.051 (4)*
C1	0	0.5775 (19)	0	0.021 (5)*
N1	0	0.4708 (19)	0	0.021 (5)*
N2	0	−0.011 (2)	0	0.021 (5)*
C2	0	0.096 (2)	0	0.021 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.351 (10)	0.255 (5)	0.90 (3)	−0.075 (5)	0.196 (17)	−0.045 (7)
I1	0.49 (5)	0.40 (3)	0.41 (4)	0.05 (3)	0	0
I2	0.44 (4)	0.68 (10)	1.1 (2)	0.20 (6)	0	0
I3	0.224 (11)	0.364 (19)	0.69 (4)	0	0	−0.39 (3)
I4	0.272 (15)	0.233 (12)	0.74 (5)	0	0	−0.06 (2)
I5	0.301 (11)	0.131 (4)	0.55 (3)	0.025 (8)	−0.090 (14)	0.027 (6)

Geometric parameters (Å, º)

Pb1—I1^i	3.069 (18)	I3—Ne1	2.45 (6)
Pb1—I2^ii	2.78 (2)	I3—C1^ix	3.02 (3)
Pb1—I3^iii	2.844 (16)	I5—Ne2^ix	3.013 (14)
Pb1—I4^iv	3.074 (16)	I5—Ne3^i	2.759 (14)
Pb1—I5^v	2.916 (12)	Ne2—N2^iii	2.88 (6)
Pb1—I5^vi	2.825 (12)	Ne2—C2^iii	3.09 (6)
Pb1—Ne1^iii	3.29 (3)	Ne3—C1^x	2.95 (2)
I1—Ne2^vii	2.29 (8)	Ne3—N1^x	3.05 (2)
I1—Ne3^viii	2.92 (4)	C1—N1	1.22 (3)
I2—Ne2	2.38 (10)	N2—C2	1.22 (3)
I2—C2^iii	2.92 (5)
I1^i—Pb1—I2^ii	177.0 (13)	I5^v—Pb1—Ne1^iii	81.6 (8)
I1^i—Pb1—I3^iii	72.9 (10)	I5^vi—Pb1—Ne1^iii	104.8 (8)
I1^i—Pb1—I4^iv	80.0 (10)	Pb1^i—I1—Pb1^xi	157.1 (12)
I1^i—Pb1—I5^v	79.5 (7)	Pb1^xii—I2—Pb1^xiii	155 (3)
I1^i—Pb1—I5^vi	94.8 (8)	Pb1^xiv—I3—Pb1^xv	152.0 (13)
I1^i—Pb1—Ne1^iii	113.7 (11)	Pb1^xvi—I4—Pb1^xvii	148.5 (12)
I2^ii—Pb1—I3^iii	110.2 (13)	Pb1^xviii—I5—Pb1^xix	172.6 (7)
I2^ii—Pb1—I4^iv	97.1 (12)	I1^xx—Ne2—I2	166 (3)
I2^ii—Pb1—I5^v	100.0 (15)	I1^xx—Ne2—I5^xxi	91.4 (14)
I2^ii—Pb1—I5^vi	85.5 (14)	I1^xx—Ne2—I5^xxii	91.4 (14)
I3^iii—Pb1—I4^iv	150.5 (10)	I2—Ne2—I5^xxi	88.9 (14)
I3^iii—Pb1—I5^v	94.8 (6)	I2—Ne2—I5^xxii	88.9 (14)
I3^iii—Pb1—I5^vi	87.5 (6)	I5^xxi—Ne2—I5^xxii	176 (3)
I4^iv—Pb1—I5^v	91.3 (5)	I1^xxiii—Ne3—I5^i	99.6 (5)
I4^iv—Pb1—I5^vi	83.4 (5)	I1^xxiii—Ne3—I5^xv	99.6 (5)
I4^iv—Pb1—Ne1^iii	162.8 (11)	I5^i—Ne3—I5^xv	158.3 (9)
I5^v—Pb1—I5^vi	172.8 (7)

Symmetry codes: (i) −x+1, y, −z+1; (ii) −x+3/2, y+1/2, −z+1/2; (iii) x+1, y, z; (iv) −x+1/2, y+1/2, −z+3/2; (v) x, y+1, z; (vi) −x+3/2, y+1/2, −z+3/2; (vii) −x+1, y+1, −z; (viii) −x+1/2, y+1/2, −z+1/2; (ix) x, y, z+1; (x) x+1/2, y−1/2, z+1/2; (xi) −x+1, y, z−1; (xii) −x+3/2, y−1/2, −z+1/2; (xiii) −x+3/2, y−1/2, z−1/2; (xiv) x−1, y, z; (xv) −x+1, y, z; (xvi) −x+1/2, y−1/2, −z+3/2; (xvii) x−1/2, y−1/2, −z+3/2; (xviii) x, y−1, z; (xix) −x+3/2, y−1/2, −z+3/2; (xx) −x+1, y−1, −z; (xxi) x, y, z−1; (xxii) x, y, −z+1; (xxiii) −x+1/2, y−1/2, −z+1/2.

neon methylammonium lead iodide (V)

Crystal data

C0.25I3N0.25Ne1.412Pb	F(000) = 2067
Mr = 622.9	Dx = 5.893 Mg m^−3
Orthorhombic, Im2m	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: I -2 -2	Cell parameters from 1125 reflections
a = 11.196 (3) Å	θ = 2.7–8.3°
b = 11.197 (3) Å	µ = 16.68 mm^−1
c = 11.201 (3) Å	T = 293 K
V = 1404.2 (7) Å^3	Irregular
Z = 8

Data collection

Abstract diffractometer	163 reflections with I > 2σ(I)
Radiation source: synchrotron	Rint = 0.061
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 8.3°, θmin = 2.7°
	h = −5→5
1125 measured reflections	k = −8→8
335 independent reflections	l = −8→8

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.057	Weighting scheme based on measured s.u.'s w = 1/(σ^2(I) + 0.0016I^2)
wR(F^2) = 0.068	(Δ/σ)max = 0.046
S = 0.87	Δρmax = 0.29 e Å^−3
335 reflections	Δρmin = −0.32 e Å^−3
34 parameters	Absolute structure: 103 of Friedel pairs used in the refinement
1 restraint	Absolute structure parameter: 0.25 (6)

Special details

Experimental. High pressure P = 7.4 GPa. Ne-PTM.

Refinement. No H atoms are included into the model;Twin. 0.75 of the CH3NH3 content is in the randomly distributed and non-detectable positions. The corresponding atoms are not included into refinement. C, N and Ne atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Pb1	0.7344 (12)	0.75 (1)	0.7218 (8)	0.343 (5)*
I1	0.2554 (13)	0.7785 (15)	0	0.153 (3)*
I2	0.763 (5)	0.273 (4)	0	0.425 (13)*
I3	0	0.755 (3)	0.8147 (18)	0.342 (12)*
I4	0	0.216 (5)	0.702 (6)	0.60 (4)*
I5	0.749 (2)	0.001 (2)	0.7252 (19)	0.299 (8)*
Ne1	0	0.798 (6)	0.599 (4)	0.164 (15)*
Ne2	0.744 (13)	−0.008 (9)	0	0.24 (4)*
Ne3	0.277 (4)	0.026 (3)	0.5	0.083 (14)*
C1	0	0.551 (5)	0	0.0012*
N1	0	0.442 (5)	0	0.0012*

Geometric parameters (Å, º)

Pb1—I1^i	3.135 (10)	I2—Ne2	3.16 (11)
Pb1—I2^ii	2.498 (10)	I2—Ne3^xi	2.84 (6)
Pb1—I3^iii	3.151 (15)	I3—Ne1	2.46 (5)
Pb1—I4^iv	2.79 (2)	I3—C1^xii	3.08 (5)
Pb1—I5^v	2.81 (3)	I5—Ne2^xii	3.08 (2)
Pb1—I5^vi	2.86 (3)	I5—Ne3^i	2.56 (2)
I1—Ne2^vii	2.39 (10)	Ne3—C1^xiii	2.51 (5)
I1—Ne3^viii	2.85 (4)	Ne3—N1^xiii	2.67 (5)
I2—Ne1^ix	3.16 (5)	C1—N1	1.22 (8)
I2—Ne1^x	3.16 (5)
I1^i—Pb1—I2^ii	167.8 (11)	Ne1^x—I2—Ne2	91 (3)
I1^i—Pb1—I3^iii	68.6 (5)	Ne1^x—I2—Ne3^xi	88.2 (19)
I1^i—Pb1—I4^iv	75.1 (13)	Ne2—I2—Ne3^xi	179 (3)
I1^i—Pb1—I5^v	83.3 (5)	Pb1^xvii—I3—Pb1^xviii	141.4 (7)
I1^i—Pb1—I5^vi	83.7 (6)	Pb1^xix—I4—Pb1^xx	141 (2)
I2^ii—Pb1—I3^iii	108.3 (13)	Pb1^xxi—I5—Pb1^xxii	168.8 (9)
I2^ii—Pb1—I4^iv	109.5 (18)	I2^xxiii—Ne1—I2^viii	137.4 (17)
I2^ii—Pb1—I5^v	84.7 (11)	I2^xxiii—Ne1—I3	109.2 (10)
I2^ii—Pb1—I5^vi	107.9 (11)	I2^viii—Ne1—I3	109.2 (10)
I3^iii—Pb1—I4^iv	142.1 (13)	I1^xxiv—Ne2—I2	176 (6)
I3^iii—Pb1—I5^v	85.5 (9)	I1^xxiv—Ne2—I5^xxv	91.8 (19)
I3^iii—Pb1—I5^vi	83.6 (9)	I1^xxiv—Ne2—I5^xxvi	91.8 (19)
I4^iv—Pb1—I5^v	101.0 (13)	I2—Ne2—I5^xxv	88.1 (19)
I4^iv—Pb1—I5^vi	82.0 (13)	I2—Ne2—I5^xxvi	88.1 (19)
I5^v—Pb1—I5^vi	165.4 (8)	I5^xxv—Ne2—I5^xxvi	176 (4)
Pb1^i—I1—Pb1^xiv	167.6 (6)	I1^x—Ne3—I2^xxvii	169 (2)
Ne2^vii—I1—Ne3^viii	173 (4)	I1^x—Ne3—I5^i	95.6 (11)
Pb1^xv—I2—Pb1^xvi	168 (2)	I1^x—Ne3—I5^xviii	95.6 (11)
Ne1^ix—I2—Ne1^x	41.3 (13)	I2^xxvii—Ne3—I5^i	83.1 (11)
Ne1^ix—I2—Ne2	91 (3)	I2^xxvii—Ne3—I5^xviii	83.1 (11)
Ne1^ix—I2—Ne3^xi	88.2 (19)	I5^i—Ne3—I5^xviii	161 (2)

Symmetry codes: (i) −x+1, y, −z+1; (ii) −x+3/2, y+1/2, −z+1/2; (iii) x+1, y, z; (iv) −x+1/2, y+1/2, −z+3/2; (v) x, y+1, z; (vi) −x+3/2, y+1/2, −z+3/2; (vii) −x+1, y+1, −z; (viii) −x+1/2, y+1/2, −z+1/2; (ix) x+1/2, y−1/2, z−1/2; (x) −x+1/2, y−1/2, −z+1/2; (xi) x+1/2, y+1/2, z−1/2; (xii) x, y, z+1; (xiii) x+1/2, y−1/2, z+1/2; (xiv) −x+1, y, z−1; (xv) −x+3/2, y−1/2, −z+1/2; (xvi) −x+3/2, y−1/2, z−1/2; (xvii) x−1, y, z; (xviii) −x+1, y, z; (xix) −x+1/2, y−1/2, −z+3/2; (xx) x−1/2, y−1/2, −z+3/2; (xxi) x, y−1, z; (xxii) −x+3/2, y−1/2, −z+3/2; (xxiii) x−1/2, y+1/2, z+1/2; (xxiv) −x+1, y−1, −z; (xxv) x, y, z−1; (xxvi) x, y, −z+1; (xxvii) x−1/2, y−1/2, z+1/2.

neon lead iodide (VI)

Crystal data

I3Ne2.166Pb	F(000) = 2101
Mr = 631.6	Dx = 6.901 Mg m^−3
Tetragonal, I4/mmm	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: -I 4 2	Cell parameters from 481 reflections
a = 10.701 (5) Å	θ = 2.8–9.6°
c = 10.622 (5) Å	µ = 19.27 mm^−1
V = 1216.3 (13) Å^3	T = 293 K
Z = 8	Irregular

Data collection

Abstract diffractometer	39 reflections with I > 2σ(I)
Radiation source: synchrotron	Rint = 0.088
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 9.6°, θmin = 2.8°
	h = −9→9
481 measured reflections	k = −9→9
100 independent reflections	l = −6→5

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.051	0 constraints
wR(F^2) = 0.057	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 1.44	(Δ/σ)max = 0.047
100 reflections	Δρmax = 0.58 e Å^−3
18 parameters	Δρmin = −0.60 e Å^−3

Special details

Experimental. High pressure P = 16.43 GPa. Ne-PTM.

Refinement. No H atoms are included into the model; Twin. CH3NH3 content is in the randomly distributed and non-detectable positions. The corresponding atoms are not included into refinement. All atoms have been refined with only isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
I4	0	0	0	0.279 (10)*
Pb2	0.5	0	0.75	0.454 (9)*
I1	0.7299 (15)	0.5	0.7429 (11)	0.426 (8)*
I2	0.5	0	0.5	0.502 (18)*
I3	0	0	0.5	0.65 (4)*
Pb1	0	0	0.7269 (14)	0.511 (12)*
Ne1	0.762 (3)	0.5	0	0.140 (10)*
Ne2	0.7123 (19)	0.7123 (19)	0.710 (4)	0.109 (10)*	0.5
Ne3	0.5	0.738 (7)	0.5	0.009 (17)*	0.1659

Geometric parameters (Å, º)

I4—Pb1^i	2.900 (16)	I1—Ne2	2.31 (3)
I4—Pb1^ii	2.900 (16)	I1—Ne2^viii	2.31 (3)
I4—Ne3^iii	2.54 (8)	I1—Ne3^viii	2.581 (13)
I4—Ne3^iv	2.54 (8)	I2—Ne1^xiv	2.55 (4)
I4—Ne3^v	2.54 (8)	I2—Ne1^xv	2.55 (4)
I4—Ne3^vi	2.54 (8)	I2—Ne3^xvi	2.81 (8)
Pb2—I1^vii	2.89 (3)	I2—Ne3^xvii	2.81 (8)
Pb2—I1^viii	2.89 (3)	I3—Pb1	2.410 (15)
Pb2—I1^ix	2.89 (3)	I3—Pb1^ii	2.410 (15)
Pb2—I1^x	2.89 (3)	I3—Ne1^xiv	2.80 (4)
Pb2—I2	2.6555 (13)	I3—Ne1^xviii	2.80 (4)
Pb2—I2^xi	2.6555 (13)	I3—Ne1^xi	2.80 (4)
I1—Pb1^xii	2.48 (3)	I3—Ne1^xix	2.80 (4)
I1—Ne1^xiii	2.751 (13)
Pb1^i—I4—Pb1^ii	180.0 (5)	Pb2^v—I2—Ne3^xvii	90
Pb1^i—I4—Ne3^iii	90	Ne1^xiv—I2—Ne1^xv	180.0 (5)
Pb1^i—I4—Ne3^iv	90	Ne1^xiv—I2—Ne3^xvi	90
Pb1^i—I4—Ne3^v	90	Ne1^xiv—I2—Ne3^xvii	90
Pb1^i—I4—Ne3^vi	90	Ne1^xv—I2—Ne3^xvi	90
Pb1^ii—I4—Ne3^iii	90	Ne1^xv—I2—Ne3^xvii	90
Pb1^ii—I4—Ne3^iv	90	Ne3^xvi—I2—Ne3^xvii	180.0 (5)
Pb1^ii—I4—Ne3^v	90	Pb1—I3—Pb1^ii	180.0 (5)
Pb1^ii—I4—Ne3^vi	90	Pb1—I3—Ne1^xiv	90
Ne3^iii—I4—Ne3^iv	180.0 (5)	Pb1—I3—Ne1^xviii	90
Ne3^iii—I4—Ne3^v	90	Pb1—I3—Ne1^xi	90
Ne3^iii—I4—Ne3^vi	90	Pb1—I3—Ne1^xix	90
Ne3^iv—I4—Ne3^v	90	Pb1^ii—I3—Ne1^xiv	90
Ne3^iv—I4—Ne3^vi	90	Pb1^ii—I3—Ne1^xviii	90
Ne3^v—I4—Ne3^vi	180.0 (5)	Pb1^ii—I3—Ne1^xi	90
I1^vii—Pb2—I1^viii	177.0 (3)	Pb1^ii—I3—Ne1^xix	90
I1^vii—Pb2—I1^ix	90.038 (8)	Ne1^xiv—I3—Ne1^xviii	180.0 (5)
I1^vii—Pb2—I1^x	90.038 (8)	Ne1^xiv—I3—Ne1^xi	90
I1^vii—Pb2—I2	88.5 (2)	Ne1^xiv—I3—Ne1^xix	90
I1^vii—Pb2—I2^xi	91.5 (2)	Ne1^xviii—I3—Ne1^xi	90
I1^viii—Pb2—I1^ix	90.038 (8)	Ne1^xviii—I3—Ne1^xix	90
I1^viii—Pb2—I1^x	90.038 (8)	Ne1^xi—I3—Ne1^xix	180.0 (5)
I1^viii—Pb2—I2	88.5 (2)	I4^xiii—Pb1—I1^xxi	82.6 (4)
I1^viii—Pb2—I2^xi	91.5 (2)	I4^xiii—Pb1—I1^x	82.6 (4)
I1^ix—Pb2—I1^x	177.0 (3)	I4^xiii—Pb1—I1^xxii	82.6 (4)
I1^ix—Pb2—I2	91.5 (2)	I4^xiii—Pb1—I1^xxiii	82.6 (4)
I1^ix—Pb2—I2^xi	88.5 (2)	I4^xiii—Pb1—I3	180.0 (5)
I1^x—Pb2—I2	91.5 (2)	I1^xxi—Pb1—I1^x	165.2 (8)
I1^x—Pb2—I2^xi	88.5 (2)	I1^xxi—Pb1—I1^xxii	89.05 (10)
I2—Pb2—I2^xi	180.0 (5)	I1^xxi—Pb1—I1^xxiii	89.05 (10)
Pb2^xx—I1—Pb1^xii	171.1 (6)	I1^xxi—Pb1—I3	97.4 (4)
Pb2^xx—I1—Ne1^xiii	81.4 (7)	I1^x—Pb1—I1^xxii	89.05 (10)
Pb2^xx—I1—Ne2	94.9 (7)	I1^x—Pb1—I1^xxiii	89.05 (10)
Pb2^xx—I1—Ne2^viii	94.9 (7)	I1^x—Pb1—I3	97.4 (4)
Pb2^xx—I1—Ne3^viii	89.6 (17)	I1^xxii—Pb1—I1^xxiii	165.2 (8)
Pb1^xii—I1—Ne1^xiii	89.7 (8)	I1^xxii—Pb1—I3	97.4 (4)
Pb1^xii—I1—Ne2	86.5 (7)	I1^xxiii—Pb1—I3	97.4 (4)
Pb1^xii—I1—Ne2^viii	86.5 (7)	I1^i—Ne1—I1^xxiv	165.8 (13)
Pb1^xii—I1—Ne3^viii	99.3 (18)	I1^i—Ne1—I2^xxv	97.1 (7)
Ne1^xiii—I1—Ne2	99.2 (10)	I1^i—Ne1—I3^xxv	82.9 (7)
Ne1^xiii—I1—Ne2^viii	99.2 (10)	I1^xxiv—Ne1—I2^xxv	97.1 (7)
Ne1^xiii—I1—Ne3^viii	171.0 (19)	I1^xxiv—Ne1—I3^xxv	82.9 (7)
Ne2—I1—Ne2^viii	160.3 (14)	I2^xxv—Ne1—I3^xxv	180.0 (5)
Ne2—I1—Ne3^viii	81.5 (10)	I1—Ne2—I1^xx	98.0 (10)
Ne2^viii—I1—Ne3^viii	81.5 (10)	I1—Ne2—Ne2^xxvi	115 (2)
Pb2—I2—Pb2^v	180.0 (5)	I1^xx—Ne2—Ne2^xxvi	115 (2)
Pb2—I2—Ne1^xiv	90	I4^xxvii—Ne3—I1^xx	88.1 (17)
Pb2—I2—Ne1^xv	90	I4^xxvii—Ne3—I1^xxviii	88.1 (17)
Pb2—I2—Ne3^xvi	90	I4^xxvii—Ne3—I2^xxix	180.0 (5)
Pb2—I2—Ne3^xvii	90	I1^xx—Ne3—I1^xxviii	176 (3)
Pb2^v—I2—Ne1^xiv	90	I1^xx—Ne3—I2^xxix	91.9 (17)
Pb2^v—I2—Ne1^xv	90	I1^xxviii—Ne3—I2^xxix	91.9 (17)
Pb2^v—I2—Ne3^xvi	90

Symmetry codes: (i) x, y, z−1; (ii) −x, y, −z+1; (iii) x−1/2, y−1/2, z−1/2; (iv) −x+1/2, −y+1/2, z−1/2; (v) −y+1/2, x−1/2, z−1/2; (vi) y−1/2, −x+1/2, z−1/2; (vii) −y+1, x−1, z; (viii) y, −x+1, z; (ix) −x+3/2, y−1/2, −z+3/2; (x) x−1/2, −y+1/2, −z+3/2; (xi) −y+1/2, x−1/2, z+1/2; (xii) −x+1/2, y+1/2, −z+3/2; (xiii) x, y, z+1; (xiv) x−1/2, y−1/2, z+1/2; (xv) −x+3/2, −y+1/2, z+1/2; (xvi) x, y−1, z; (xvii) −x+1, −y+1, z; (xviii) −x+1/2, −y+1/2, z+1/2; (xix) y−1/2, −x+1/2, z+1/2; (xx) −y+1, x, z; (xxi) −x+1/2, y−1/2, −z+3/2; (xxii) y−1/2, x−1/2, −z+3/2; (xxiii) −y+1/2, −x+1/2, −z+3/2; (xxiv) x, −y+1, −z+1; (xxv) x+1/2, y+1/2, z−1/2; (xxvi) −y+3/2, −x+3/2, −z+3/2; (xxvii) x+1/2, y+1/2, z+1/2; (xxviii) y, x, −z+1; (xxix) x, y+1, z.

neon lead iodide (VII)

Crystal data

I3Ne2.5Pb	F(000) = 2128
Mr = 638.4	Dx = 7.357 Mg m^−3
Tetragonal, I4/mmm	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: -I 4;-2	Cell parameters from 380 reflections
a = 10.538 (5) Å	θ = 2.9–8.8°
c = 10.379 (5) Å	µ = 20.34 mm^−1
V = 1152.6 (12) Å^3	T = 293 K
Z = 8	Irregular

Data collection

Abstract diffractometer	32 reflections with I > 2σ(I)
Radiation source: synchrotron	Rint = 0.082
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 8.8°, θmin = 2.9°
	h = −8→8
380 measured reflections	k = −8→8
78 independent reflections	l = −5→5

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.043	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.058	(Δ/σ)max = 0.049
S = 1.52	Δρmax = 0.81 e Å^−3
78 reflections	Δρmin = −1.35 e Å^−3
19 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 2400 (900)

Special details

Experimental. High pressure P = 20.27 GPa. Ne-PTM.

Refinement. CH3NH3 is in the randomly distributed positions. No H, C and N atoms are included into the model; Twin. All atoms have been refined with only isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
I4	0	0	0	0.166 (15)*
Pb2	0.5	0	0.75	0.254 (14)*
I1	0.740 (2)	0.5	0.7575 (15)	0.254 (14)*
I2	0.5	0	0.5	0.8 (2)*	0.5
I3	0	0	0.5	0.40 (6)*
Pb1	0	0	0.745 (2)	0.367 (15)*
Ne1	0.787 (4)	0.5	0	0.089 (18)*
Ne2	0.7143 (18)	0.7143 (18)	0.657 (7)	0.002 (14)*	0.5
Ne3	0.5	0.751 (11)	0.5	0.17 (5)*	0.5

Geometric parameters (Å, º)

I4—Pb1^i	2.65 (2)	I1—Ne1^xiii	2.566 (18)
I4—Pb1^ii	2.65 (2)	I1—Ne2	2.50 (3)
I4—Ne3^iii	2.65 (11)	I1—Ne2^viii	2.50 (3)
I4—Ne3^iv	2.65 (11)	I1—Ne3^viii	2.675 (17)
I4—Ne3^v	2.65 (11)	I2—Ne1^xiv	2.24 (4)
I4—Ne3^vi	2.65 (11)	I2—Ne1^xv	2.24 (4)
Pb2—I1^vii	2.74 (2)	I2—Ne3^xvi	2.62 (11)
Pb2—I1^viii	2.74 (2)	I2—Ne3^xvii	2.62 (11)
Pb2—I1^ix	2.74 (2)	I3—Pb1	2.54 (2)
Pb2—I1^x	2.74 (2)	I3—Pb1^ii	2.54 (2)
Pb2—I2	2.595 (3)	Ne2—Ne3	2.81 (5)
Pb2—I2^xi	2.595 (3)	Ne2—Ne3^viii	2.81 (5)
I1—Pb1^xii	2.53 (2)
Pb1^i—I4—Pb1^ii	180.0 (5)	Ne1^xv—I2—Ne3^xvii	90
Pb1^i—I4—Ne3^iii	90	Ne3^xvi—I2—Ne3^xvii	180.0 (5)
Pb1^i—I4—Ne3^iv	90	Pb1—I3—Pb1^ii	180.0 (5)
Pb1^i—I4—Ne3^v	90	I4^xiii—Pb1—I1^xix	90.5 (6)
Pb1^i—I4—Ne3^vi	90	I4^xiii—Pb1—I1^x	90.5 (6)
Pb1^ii—I4—Ne3^iii	90	I4^xiii—Pb1—I1^xx	90.5 (6)
Pb1^ii—I4—Ne3^iv	90	I4^xiii—Pb1—I1^xxi	90.5 (6)
Pb1^ii—I4—Ne3^v	90	I4^xiii—Pb1—I3	180.0 (5)
Pb1^ii—I4—Ne3^vi	90	I1^xix—Pb1—I1^x	179.0 (11)
Ne3^iii—I4—Ne3^iv	180.0 (5)	I1^xix—Pb1—I1^xx	89.995 (10)
Ne3^iii—I4—Ne3^v	90	I1^xix—Pb1—I1^xxi	89.995 (10)
Ne3^iii—I4—Ne3^vi	90	I1^xix—Pb1—I3	89.5 (6)
Ne3^iv—I4—Ne3^v	90	I1^x—Pb1—I1^xx	89.995 (10)
Ne3^iv—I4—Ne3^vi	90	I1^x—Pb1—I1^xxi	89.995 (10)
Ne3^v—I4—Ne3^vi	180.0 (5)	I1^x—Pb1—I3	89.5 (6)
I1^vii—Pb2—I1^viii	176.7 (5)	I1^xx—Pb1—I1^xxi	179.0 (11)
I1^vii—Pb2—I1^ix	90.047 (13)	I1^xx—Pb1—I3	89.5 (6)
I1^vii—Pb2—I1^x	90.047 (13)	I1^xxi—Pb1—I3	89.5 (6)
I1^vii—Pb2—I2	91.6 (3)	I1^i—Ne1—I1^xxii	157.6 (19)
I1^vii—Pb2—I2^xi	88.4 (3)	I1^i—Ne1—I2^xxiii	101.2 (10)
I1^viii—Pb2—I1^ix	90.047 (13)	I1^xxii—Ne1—I2^xxiii	101.2 (10)
I1^viii—Pb2—I1^x	90.047 (13)	I1—Ne2—I1^xviii	91.2 (16)
I1^viii—Pb2—I2	91.6 (3)	I1—Ne2—Ne2^xxiv	84 (2)
I1^viii—Pb2—I2^xi	88.4 (3)	I1—Ne2—Ne3	117 (2)
I1^ix—Pb2—I1^x	176.7 (5)	I1^xviii—Ne2—Ne2^xxiv	84 (2)
I1^ix—Pb2—I2	88.4 (3)	I1^xviii—Ne2—Ne3^viii	117 (2)
I1^ix—Pb2—I2^xi	91.6 (3)	Ne2^xxiv—Ne2—Ne3	137 (2)
I1^x—Pb2—I2	88.4 (3)	Ne2^xxiv—Ne2—Ne3^viii	137 (2)
I1^x—Pb2—I2^xi	91.6 (3)	Ne3—Ne2—Ne3^viii	84 (3)
I2—Pb2—I2^xi	180.0 (5)	I4^xxv—Ne3—I1^xviii	87 (2)
Pb2^xviii—I1—Pb1^xii	177.9 (8)	I4^xxv—Ne3—I1^xxvi	87 (2)
Pb2^xviii—I1—Ne1^xiii	80.4 (10)	I4^xxv—Ne3—I2^xxvii	180.0 (5)
Pb2^xviii—I1—Ne2	95.6 (7)	I4^xxv—Ne3—Ne2	82 (2)
Pb2^xviii—I1—Ne2^viii	95.6 (7)	I4^xxv—Ne3—Ne2^xviii	82 (2)
Pb2^xviii—I1—Ne3^viii	86 (2)	I4^xxv—Ne3—Ne2^xxviii	82 (2)
Pb1^xii—I1—Ne1^xiii	101.7 (12)	I4^xxv—Ne3—Ne2^xxvi	82 (2)
Pb1^xii—I1—Ne2	83.5 (7)	I1^xviii—Ne3—I1^xxvi	175 (5)
Pb1^xii—I1—Ne2^viii	83.5 (7)	I1^xviii—Ne3—I2^xxvii	93 (2)
Pb1^xii—I1—Ne3^viii	92 (3)	I1^xviii—Ne3—Ne2^xxviii	124.9 (15)
Ne1^xiii—I1—Ne2	115.5 (15)	I1^xviii—Ne3—Ne2^xxvi	124.9 (15)
Ne1^xiii—I1—Ne2^viii	115.5 (15)	I1^xxvi—Ne3—I2^xxvii	93 (2)
Ne1^xiii—I1—Ne3^viii	166 (3)	I1^xxvi—Ne3—Ne2	124.9 (15)
Ne2—I1—Ne2^viii	129 (2)	I1^xxvi—Ne3—Ne2^xviii	124.9 (15)
Pb2—I2—Pb2^v	180.0 (5)	I1^xxvi—Ne3—Ne2^xxviii	54.3 (12)
Pb2—I2—Ne1^xiv	90	I1^xxvi—Ne3—Ne2^xxvi	54.3 (12)
Pb2—I2—Ne1^xv	90	I2^xxvii—Ne3—Ne2	98 (2)
Pb2—I2—Ne3^xvi	90	I2^xxvii—Ne3—Ne2^xviii	98 (2)
Pb2—I2—Ne3^xvii	90	I2^xxvii—Ne3—Ne2^xxviii	98 (2)
Pb2^v—I2—Ne1^xiv	90	I2^xxvii—Ne3—Ne2^xxvi	98 (2)
Pb2^v—I2—Ne1^xv	90	Ne2—Ne3—Ne2^xviii	107.0 (18)
Pb2^v—I2—Ne3^xvi	90	Ne2—Ne3—Ne2^xxviii	164 (5)
Pb2^v—I2—Ne3^xvii	90	Ne2—Ne3—Ne2^xxvi	70.7 (17)
Ne1^xiv—I2—Ne1^xv	180.0 (5)	Ne2^xviii—Ne3—Ne2^xxviii	70.7 (17)
Ne1^xiv—I2—Ne3^xvi	90	Ne2^xviii—Ne3—Ne2^xxvi	164 (5)
Ne1^xiv—I2—Ne3^xvii	90	Ne2^xxviii—Ne3—Ne2^xxvi	107.0 (18)
Ne1^xv—I2—Ne3^xvi	90

Symmetry codes: (i) x, y, z−1; (ii) −x, y, −z+1; (iii) x−1/2, y−1/2, z−1/2; (iv) −x+1/2, −y+1/2, z−1/2; (v) −y+1/2, x−1/2, z−1/2; (vi) y−1/2, −x+1/2, z−1/2; (vii) −y+1, x−1, z; (viii) y, −x+1, z; (ix) −x+3/2, y−1/2, −z+3/2; (x) x−1/2, −y+1/2, −z+3/2; (xi) −y+1/2, x−1/2, z+1/2; (xii) −x+1/2, y+1/2, −z+3/2; (xiii) x, y, z+1; (xiv) x−1/2, y−1/2, z+1/2; (xv) −x+3/2, −y+1/2, z+1/2; (xvi) x, y−1, z; (xvii) −x+1, −y+1, z; (xviii) −y+1, x, z; (xix) −x+1/2, y−1/2, −z+3/2; (xx) y−1/2, x−1/2, −z+3/2; (xxi) −y+1/2, −x+1/2, −z+3/2; (xxii) x, −y+1, −z+1; (xxiii) x+1/2, y+1/2, z−1/2; (xxiv) −y+3/2, −x+3/2, −z+3/2; (xxv) x+1/2, y+1/2, z+1/2; (xxvi) y, x, −z+1; (xxvii) x, y+1, z; (xxviii) −x+1, y, −z+1.

neon methylammonium lead iodide (VIII)

Crystal data

CH6I3NNe0.973Pb	F(000) = 1078
Mr = 639.3	Dx = 4.253 Mg m^−3
Tetragonal, I422	Synchrotron radiation, λ = 0.7153 Å
Hall symbol: I 4 2	Cell parameters from 3819 reflections
a = 8.876 (1) Å	θ = 2.8–31.9°
c = 12.672 (1) Å	µ = 26.32 mm^−1
V = 998.3 (2) Å^3	T = 293 K
Z = 4	Irregular

Data collection

Dectris-CrysAlisPro-abstract goniometer imported dectris images diffractometer	1096 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.029
Synchrotron monochromator	θmax = 31.9°, θmin = 2.8°
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −11→11
	k = −12→12
3819 measured reflections	l = −18→18
1453 independent reflections

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
R[F^2 > 2σ(F^2)] = 0.035	(Δ/σ)max = 0.050
wR(F^2) = 0.049	Δρmax = 1.43 e Å^−3
S = 1.73	Δρmin = −0.87 e Å^−3
1453 reflections	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
76 parameters	Extinction coefficient: 510 (80)
1 restraint	Absolute structure: 319 of Friedel pairs used in the refinement
24 constraints	Absolute structure parameter: 0.48 (2)
H-atom parameters constrained

Special details

Refinement. Twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0	0	0.7481 (3)	0.0793 (11)
I1_1	0	0	0.5	0.104 (3)
I1_2	0	0	0	0.224 (8)
I2	0.2794 (4)	0.7794 (4)	0.75	0.1378 (17)
C	1.002 (8)	0.465 (5)	0.531 (3)	0.10 (2)*	0.25
N	0.941 (5)	0.615 (4)	0.513 (3)	0.095 (14)*	0.25
H1n	0.95179	0.676224	0.578975	0.1137*	0.25
H2n	0.83164	0.606715	0.494402	0.1137*	0.25
H3n	0.996441	0.664975	0.454213	0.1137*	0.25
H1c	0.918286	0.390407	0.535278	0.1141*	0.25
H2c	1.061096	0.464058	0.598032	0.1141*	0.25
H3c	1.070306	0.437611	0.470671	0.1141*	0.25
Ne	0	0.5	0.25	0.102 (14)*	0.277 (15)
Ne2	−0.223 (4)	0.685 (5)	0.498 (2)	0.113 (12)*	0.174 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0720 (15)	0.0720 (15)	0.094 (2)	0	0	0
I1_1	0.122 (5)	0.122 (5)	0.068 (5)	0	0	0
I1_2	0.303 (16)	0.303 (16)	0.066 (6)	0	0	0
I2	0.120 (2)	0.120 (2)	0.174 (4)	0.035 (2)	−0.0028 (12)	0.0028 (12)

Geometric parameters (Å, º)

Pb1—I1_1	3.144 (4)	I2—Ne2^xvi	3.29 (3)
Pb1—I1_2^i	3.192 (4)	I2—Ne2^xvii	3.29 (3)
Pb1—I2^ii	3.160 (4)	I2—Ne2^xviii	3.21 (3)
Pb1—I2^iii	3.160 (4)	C—N	1.46 (7)
Pb1—I2^iv	3.160 (4)	C—N^xix	1.53 (6)
Pb1—I2^v	3.160 (4)	C—Ne^xx	2.80 (4)
I1_2—Ne2^vi	2.96 (4)	C—Ne2^xxi	2.83 (7)
I1_2—Ne2^vii	2.96 (4)	C—Ne2^xxii	2.41 (7)
I1_2—Ne2^viii	2.96 (4)	C—Ne2^xxiii	2.79 (7)
I1_2—Ne2^ix	2.96 (4)	C—Ne2^xxiv	2.43 (8)
I1_2—Ne2^x	2.96 (4)	N—Ne^xx	3.21 (4)
I1_2—Ne2^xi	2.96 (4)	N—Ne2^xxiii	2.59 (6)
I1_2—Ne2^xii	2.96 (4)	N—Ne2^xxiv	3.04 (6)
I1_2—Ne2^xiii	2.96 (4)	N—Ne2^xxv	2.69 (6)
I2—Ne^xiv	2.770 (4)	Ne2—Ne2^xxvi	3.29 (6)
I2—Ne2^xv	3.21 (3)
I1_1—Pb1—I1_2^i	180.0 (5)	C^xxviii—N—Ne^xx	55 (3)
I1_1—Pb1—I2^ii	90.43 (8)	C^xxviii—N—Ne2^xxi	148 (6)
I1_1—Pb1—I2^iii	90.43 (8)	C^xxviii—N—Ne2^xxiii	70 (5)
I1_1—Pb1—I2^iv	90.43 (8)	C^xxviii—N—Ne2^xxiv	66 (5)
I1_1—Pb1—I2^v	90.43 (8)	C^xxviii—N—Ne2^xxv	155 (5)
I1_2^i—Pb1—I2^ii	89.57 (8)	C^xix—N—Ne^xx	91 (2)
I1_2^i—Pb1—I2^iii	89.57 (8)	C^xix—N—Ne2^xxi	127 (4)
I1_2^i—Pb1—I2^iv	89.57 (8)	C^xix—N—Ne2^xxiii	83 (3)
I1_2^i—Pb1—I2^v	89.57 (8)	C^xix—N—Ne2^xxv	137 (3)
I2^ii—Pb1—I2^iii	179.13 (15)	C^xxvi—N—Ne^xx	101 (3)
I2^ii—Pb1—I2^iv	90.00 (10)	C^xxvi—N—Ne2^xxi	132 (5)
I2^ii—Pb1—I2^v	90.00 (10)	C^xxvi—N—Ne2^xxiii	68 (4)
I2^iii—Pb1—I2^iv	90.00 (10)	C^xxvi—N—Ne2^xxiv	69 (4)
I2^iii—Pb1—I2^v	90.00 (10)	C^xxvi—N—Ne2^xxv	140 (4)
I2^iv—Pb1—I2^v	179.13 (15)	I2^xxix—Ne—C^xxx	94.8 (13)
Pb1—I1_1—Pb1^xvii	180.0 (5)	I2^xxix—Ne—C^xxxi	85.2 (13)
Pb1^xxvii—I1_2—Pb1^xvii	180.0 (5)	I2^xxix—Ne—C^xxiii	85.2 (13)
Ne2^vi—I1_2—Ne2^vii	178.8 (7)	I2^xxix—Ne—C^xxxii	94.8 (13)
Ne2^vi—I1_2—Ne2^viii	90.0 (11)	I2^xxix—Ne—N^xxx	70.1 (7)
Ne2^vi—I1_2—Ne2^ix	90.0 (11)	I2^xxix—Ne—N^xxxi	109.9 (7)
Ne2^vi—I1_2—Ne2^x	112.4 (11)	I2^xxix—Ne—N^xxiii	109.9 (7)
Ne2^vi—I1_2—Ne2^xi	67.6 (11)	I2^xxix—Ne—N^xxxii	70.1 (7)
Ne2^vi—I1_2—Ne2^xiii	157.6 (11)	I2^xxxiii—Ne—C^xxx	85.2 (13)
Ne2^vii—I1_2—Ne2^viii	90.0 (11)	I2^xxxiii—Ne—C^xxxi	94.8 (13)
Ne2^vii—I1_2—Ne2^ix	90.0 (11)	I2^xxxiii—Ne—C^xxiii	94.8 (13)
Ne2^vii—I1_2—Ne2^x	67.6 (11)	I2^xxxiii—Ne—C^xxxii	85.2 (13)
Ne2^vii—I1_2—Ne2^xi	112.4 (11)	I2^xxxiii—Ne—N^xxx	109.9 (7)
Ne2^vii—I1_2—Ne2^xii	157.6 (11)	I2^xxxiii—Ne—N^xxxi	70.1 (7)
Ne2^viii—I1_2—Ne2^ix	178.8 (7)	I2^xxxiii—Ne—N^xxiii	70.1 (7)
Ne2^viii—I1_2—Ne2^xi	157.6 (11)	I2^xxxiii—Ne—N^xxxii	109.9 (7)
Ne2^viii—I1_2—Ne2^xii	67.6 (11)	C^xxx—Ne—N^xxiii	155.2 (15)
Ne2^viii—I1_2—Ne2^xiii	112.4 (11)	C^xxx—Ne—N^xxxii	161.6 (16)
Ne2^ix—I1_2—Ne2^x	157.6 (11)	C^xxxi—Ne—N^xxiii	161.6 (16)
Ne2^ix—I1_2—Ne2^xii	112.4 (11)	C^xxxi—Ne—N^xxxii	155.2 (15)
Ne2^ix—I1_2—Ne2^xiii	67.6 (11)	C^xxiii—Ne—N^xxx	155.2 (15)
Ne2^x—I1_2—Ne2^xi	178.8 (7)	C^xxiii—Ne—N^xxxi	161.6 (16)
Ne2^x—I1_2—Ne2^xii	90.0 (11)	C^xxxii—Ne—N^xxx	161.6 (16)
Ne2^x—I1_2—Ne2^xiii	90.0 (11)	C^xxxii—Ne—N^xxxi	155.2 (15)
Ne2^xi—I1_2—Ne2^xii	90.0 (11)	I1_2^xxxiv—Ne2—I2^viii	91.4 (8)
Ne2^xi—I1_2—Ne2^xiii	90.0 (11)	I1_2^xxxiv—Ne2—I2^xxxv	92.9 (9)
Ne2^xii—I1_2—Ne2^xiii	178.8 (7)	I1_2^xxxiv—Ne2—C^xxxvi	101.7 (18)
Ne^xiv—I2—Ne2^xv	86.3 (7)	I1_2^xxxiv—Ne2—C^xxii	111 (2)
Ne^xiv—I2—Ne2^xvi	106.7 (7)	I1_2^xxxiv—Ne2—C^xxiii	101.3 (19)
Ne^xiv—I2—Ne2^xvii	106.7 (7)	I1_2^xxxiv—Ne2—C^xxxii	112 (2)
Ne^xiv—I2—Ne2^xviii	86.3 (7)	I1_2^xxxiv—Ne2—N^xxxvi	123 (3)
Ne2^xv—I2—Ne2^xvi	167.0 (10)	I1_2^xxxiv—Ne2—N^xxiii	132.2 (19)
Ne2^xv—I2—Ne2^xviii	172.6 (10)	I1_2^xxxiv—Ne2—N^xxxii	84.9 (14)
Ne2^xvi—I2—Ne2^xvii	146.6 (10)	I1_2^xxxiv—Ne2—N^xxxvii	91.5 (13)
Ne2^xvii—I2—Ne2^xviii	167.0 (10)	I2^viii—Ne2—I2^xxxv	157.9 (15)
N—C—Ne^xx	93 (2)	I2^viii—Ne2—C^xxxvi	115.1 (13)
N—C—Ne2^xxii	142 (4)	I2^viii—Ne2—C^xxii	115.5 (15)
N—C—Ne2^xxiii	67 (3)	I2^viii—Ne2—C^xxiii	99.3 (12)
N—C—Ne2^xxiv	100 (4)	I2^viii—Ne2—C^xxxii	97.1 (13)
N^xxviii—C—Ne^xx	110 (4)	I2^viii—Ne2—N^xxxvi	110.9 (18)
N^xxviii—C—Ne2^xxi	155 (5)	I2^viii—Ne2—N^xxiii	99.1 (12)
N^xxviii—C—Ne2^xxiii	97 (6)	I2^viii—Ne2—N^xxxii	104.6 (11)
N^xxviii—C—Ne2^xxiv	90 (5)	I2^viii—Ne2—N^xxxvii	69.9 (11)
N^xix—C—Ne^xx	106 (3)	I2^xxxv—Ne2—C^xxxvi	85.1 (11)
N^xix—C—Ne2^xxi	65 (3)	I2^xxxv—Ne2—C^xxii	82.8 (13)
N^xix—C—Ne2^xxii	99 (4)	I2^xxxv—Ne2—C^xxiii	101.0 (13)
N^xix—C—Ne2^xxiv	134 (4)	I2^xxxv—Ne2—C^xxxii	101.2 (14)
N^xxvi—C—Ne^xx	126 (4)	I2^xxxv—Ne2—N^xxxvi	84.8 (17)
N^xxvi—C—Ne2^xxi	91 (5)	I2^xxxv—Ne2—N^xxiii	94.0 (12)
N^xxvi—C—Ne2^xxii	88 (4)	I2^xxxv—Ne2—N^xxxii	97.3 (12)
N^xxvi—C—Ne2^xxiii	140 (4)	I2^xxxv—Ne2—N^xxxvii	88.4 (12)
C—N—Ne^xx	60 (2)	C^xxxvi—Ne2—N^xxxvii	166 (2)
C—N—Ne2^xxi	136 (4)	C^xxii—Ne2—N^xxxvii	156 (2)
C—N—Ne2^xxiii	82 (3)	C^xxiii—Ne2—N^xxxvii	164 (2)
C—N—Ne2^xxv	144 (4)	C^xxxii—Ne2—N^xxxvii	154 (2)

Symmetry codes: (i) x, y, z+1; (ii) x, y−1, z; (iii) −x, −y+1, z; (iv) −y+1, x, z; (v) y−1, −x, z; (vi) x+1/2, y−1/2, z−1/2; (vii) −x−1/2, −y+1/2, z−1/2; (viii) −y+1/2, x+1/2, z−1/2; (ix) y−1/2, −x−1/2, z−1/2; (x) −x−1/2, y−1/2, −z+1/2; (xi) x+1/2, −y+1/2, −z+1/2; (xii) y−1/2, x+1/2, −z+1/2; (xiii) −y+1/2, −x−1/2, −z+1/2; (xiv) x+1/2, y+1/2, z+1/2; (xv) −y+1, x+1, z; (xvi) y−1/2, −x+1/2, z+1/2; (xvii) −x, y, −z+1; (xviii) x+1/2, −y+3/2, −z+3/2; (xix) −x+2, y, −z+1; (xx) −y+3/2, x+1/2, z+1/2; (xxi) x+1, y, z; (xxii) −x+1, −y+1, z; (xxiii) −x+1, y, −z+1; (xxiv) x+1, −y+1, −z+1; (xxv) y, x+1, −z+1; (xxvi) x, −y+1, −z+1; (xxvii) x, y, z−1; (xxviii) −x+2, −y+1, z; (xxix) x−1/2, y−1/2, z−1/2; (xxx) −y+1/2, x−1/2, z−1/2; (xxxi) y−1/2, −x+3/2, z−1/2; (xxxii) x−1, −y+1, −z+1; (xxxiii) −x+1/2, −y+3/2, z−1/2; (xxxiv) x−1/2, y+1/2, z+1/2; (xxxv) y−1, −x+1, z; (xxxvi) x−1, y, z; (xxxvii) y−1, x, −z+1.

argon methylammonium lead iodide (IX)

Crystal data

I3Pb·(CN)·0.756(Ar)	F(000) = 1070
Mr = 650.2	Dx = 4.404 Mg m^−3
Tetragonal, P42bc	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: P 4c -2ab	Cell parameters from 887 reflections
a = 8.850 (5) Å	θ = 2.7–13.5°
c = 12.520 (5) Å	µ = 4.95 mm^−1
V = 980.6 (12) Å^3	T = 293 K
Z = 4	Irregular

Data collection

Abstract diffractometer	95 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.098
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.5°, θmin = 2.7°
	h = −9→9
887 measured reflections	k = −9→9
211 independent reflections	l = −14→14

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
R[F^2 > 2σ(F^2)] = 0.049	(Δ/σ)max = 0.047
wR(F^2) = 0.073	Δρmax = 2.62 e Å^−3
S = 1.44	Δρmin = −2.36 e Å^−3
211 reflections	Absolute structure: 211 of Friedel pairs used in the refinement
28 parameters	Absolute structure parameter: 0.076 (12)
1 restraint

Special details

Experimental. High pressure P = 0.18 GPa; Ar-PTM

Refinement. No H atoms are included into the model; Twin. C , N and Ar atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	0.0000 (12)	0.092 (6)
I2	0.7430 (19)	0.258 (2)	0.005 (5)	0.22 (3)
I1	0	0.5	0.752 (5)	0.24 (8)
C1	0.5	0.5	0.247 (16)	0.15 (4)*
N1	0.5	0.5	0.343 (16)	0.15 (4)*
Ar	0.847 (7)	0.277 (6)	0.227 (6)	0.041 (19)*	0.378 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.205 (16)	0.030 (4)	0.043 (5)	0.062 (4)	0	0
I2	0.19 (5)	0.24 (5)	0.25 (4)	−0.13 (4)	−0.06 (3)	−0.07 (3)
I1	0.40 (18)	0.30 (14)	0.018 (14)	0.08 (4)	0	0

Geometric parameters (Å, º)

Pb1—I2	3.136 (18)	I1—Ar^vi	2.41 (6)
Pb1—I2^i	3.136 (18)	I1—Ar^vii	2.41 (6)
Pb1—I2^ii	3.126 (18)	C1—N1	1.2 (3)
Pb1—I2^iii	3.126 (18)	C1—Ar^ii	2.82 (6)
Pb1—I1^iv	3.17 (7)	C1—Ar^viii	2.82 (6)
Pb1—I1^v	3.09 (7)	N1—Ar^ii	3.16 (11)
I2—Ar	2.93 (9)	N1—Ar^viii	3.16 (11)
I2—Pb1—I2^i	177.3 (17)	Pb1^x—I1—Pb1^xi	180.0 (5)
I2—Pb1—I2^ii	90.0 (5)	Pb1^x—I1—Ar^vi	82 (2)
I2—Pb1—I2^iii	90.0 (5)	Pb1^x—I1—Ar^vii	82 (2)
I2—Pb1—I1^iv	88.7 (12)	Pb1^xi—I1—Ar^vi	98 (2)
I2—Pb1—I1^v	91.3 (12)	Pb1^xi—I1—Ar^vii	98 (2)
I2^i—Pb1—I2^ii	90.0 (5)	Ar^vi—I1—Ar^vii	165 (4)
I2^i—Pb1—I2^iii	90.0 (5)	N1—C1—Ar^ii	95 (4)
I2^i—Pb1—I1^iv	88.7 (12)	N1—C1—Ar^viii	95 (4)
I2^i—Pb1—I1^v	91.3 (12)	Ar^ii—C1—Ar^viii	170 (8)
I2^ii—Pb1—I2^iii	177.3 (17)	C1—N1—Ar^ii	63 (3)
I2^ii—Pb1—I1^iv	88.6 (12)	C1—N1—Ar^viii	63 (3)
I2^ii—Pb1—I1^v	91.4 (12)	Ar^ii—N1—Ar^viii	125 (7)
I2^iii—Pb1—I1^iv	88.6 (12)	I2—Ar—I1^xii	110 (3)
I2^iii—Pb1—I1^v	91.4 (12)	I2—Ar—C1^ix	101 (4)
I1^iv—Pb1—I1^v	180.0 (5)	I2—Ar—N1^ix	122 (4)
Pb1—I2—Pb1^ix	175.7 (15)	I1^xii—Ar—C1^ix	115 (2)
Pb1—I2—Ar	106.3 (19)	I1^xii—Ar—N1^ix	109 (3)
Pb1^ix—I2—Ar	75.7 (15)	C1^ix—Ar—N1^ix	22 (5)

Symmetry codes: (i) −x+1, −y, z; (ii) x−1/2, −y+1/2, z; (iii) −x+3/2, y−1/2, z; (iv) −y+1, x, z−1/2; (v) x+1/2, −y+1/2, z−1; (vi) −y+1/2, −x+3/2, z+1/2; (vii) y−1/2, x−1/2, z+1/2; (viii) −x+3/2, y+1/2, z; (ix) x+1/2, −y+1/2, z; (x) −y, x, z+1/2; (xi) x−1/2, −y+1/2, z+1; (xii) −y+3/2, −x+1/2, z−1/2.

argon methylammonium lead iodide (X)

Crystal data

I3Pb·(CN)·Ar	F(000) = 1088
Mr = 659.9	Dx = 4.621 Mg m^−3
Tetragonal, P42bc	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: P 4c -2ab	Cell parameters from 1057 reflections
a = 8.7468 (15) Å	θ = 2.7–13.6°
c = 12.398 (1) Å	µ = 5.13 mm^−1
V = 948.5 (3) Å^3	T = 293 K
Z = 4	Irregular

Data collection

Abstract diffractometer	99 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.106
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.6°, θmin = 2.7°
	h = −9→9
1057 measured reflections	k = −9→9
210 independent reflections	l = −14→14

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.068	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.086	(Δ/σ)max = 0.047
S = 1.80	Δρmax = 3.78 e Å^−3
210 reflections	Δρmin = −3.57 e Å^−3
28 parameters	Absolute structure: 102 of Friedel pairs used in the refinement
1 restraint	Absolute structure parameter: 0.02 (9)

Special details

Experimental. High pressure P=0.49 GPa; Ar PTM

Refinement. No H atoms are included into the model; Twin C , N and Ar atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	0	0.102 (6)
I2	0.736 (2)	0.252 (2)	−0.040 (3)	0.179 (16)
I1	0	0.5	0.755 (3)	0.45 (9)
N1	0.5	0.5	0.3990 (14)	0.020 (16)*
C1	0.5	0.5	0.3041 (14)	0.020 (16)*
Ar	0.831 (3)	0.278 (3)	0.229 (2)	0.0046 (16)*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.031 (5)	0.234 (16)	0.041 (4)	0.066 (5)	0	0
I2	0.21 (3)	0.13 (2)	0.20 (3)	−0.08 (2)	0.08 (2)	0.08 (2)
I1	0.44 (14)	0.9 (2)	0.011 (10)	0.39 (13)	0	0

Geometric parameters (Å, º)

Pb1—I2	3.06 (2)	I2—Ar	3.45 (4)
Pb1—I2^i	3.06 (2)	I2—Ar^vii	2.96 (4)
Pb1—I2^ii	3.21 (2)	I1—Ar^viii	2.46 (2)
Pb1—I2^iii	3.21 (2)	I1—Ar^ix	2.46 (2)
Pb1—I1^iv	3.16 (4)	N1—C1	1.176 (18)
Pb1—I1^v	3.04 (4)	C1—Ar^ii	2.99 (2)
I2—N1^iv	3.08 (2)	C1—Ar^x	2.99 (2)
I2—N1^vi	3.28 (2)
I2—Pb1—I2^i	161.2 (9)	N1^vi—I2—Ar^vii	81.3 (8)
I2—Pb1—I2^ii	88.4 (5)	Ar—I2—Ar^vii	152.8 (9)
I2—Pb1—I2^iii	88.6 (5)	Pb1^xii—I1—Pb1^xiii	180.0 (5)
I2—Pb1—I1^iv	99.4 (6)	Pb1^xii—I1—Ar^viii	82.5 (11)
I2—Pb1—I1^v	80.6 (6)	Pb1^xii—I1—Ar^ix	82.5 (11)
I2^i—Pb1—I2^ii	88.6 (5)	Pb1^xiii—I1—Ar^viii	97.5 (11)
I2^i—Pb1—I2^iii	88.4 (5)	Pb1^xiii—I1—Ar^ix	97.5 (11)
I2^i—Pb1—I1^iv	99.4 (6)	Ar^viii—I1—Ar^ix	165 (2)
I2^i—Pb1—I1^v	80.6 (6)	I2^xiv—N1—I2^xv	151.8 (8)
I2^ii—Pb1—I2^iii	162.0 (8)	I2^xiv—N1—I2^viii	86.9 (5)
I2^ii—Pb1—I1^iv	99.0 (6)	I2^xiv—N1—I2^xvi	86.7 (5)
I2^ii—Pb1—I1^v	81.0 (6)	I2^xiv—N1—C1	104.1 (6)
I2^iii—Pb1—I1^iv	99.0 (6)	I2^xv—N1—I2^viii	86.7 (5)
I2^iii—Pb1—I1^v	81.0 (6)	I2^xv—N1—I2^xvi	86.9 (5)
I1^iv—Pb1—I1^v	180.0 (5)	I2^xv—N1—C1	104.1 (6)
Pb1—I2—Pb1^xi	161.2 (12)	I2^viii—N1—I2^xvi	153.5 (8)
Pb1—I2—N1^iv	95.5 (5)	I2^viii—N1—C1	103.2 (6)
Pb1—I2—N1^vi	91.5 (5)	I2^xvi—N1—C1	103.2 (6)
Pb1—I2—Ar	92.9 (9)	N1—C1—Ar^ii	108.2 (7)
Pb1—I2—Ar^vii	114.1 (10)	N1—C1—Ar^x	108.2 (7)
Pb1^xi—I2—N1^iv	92.6 (5)	Ar^ii—C1—Ar^x	143.7 (10)
Pb1^xi—I2—N1^vi	89.0 (5)	I2—Ar—I2^xvi	150.5 (10)
Pb1^xi—I2—Ar	68.4 (7)	I2—Ar—I1^vi	108.8 (13)
Pb1^xi—I2—Ar^vii	84.5 (7)	I2—Ar—C1^xi	111.6 (9)
N1^iv—I2—N1^vi	152.5 (11)	I2^xvi—Ar—I1^vi	96.4 (13)
N1^iv—I2—Ar	110.6 (8)	I2^xvi—Ar—C1^xi	73.4 (8)
N1^iv—I2—Ar^vii	71.6 (8)	I1^vi—Ar—C1^xi	107.7 (9)
N1^vi—I2—Ar	95.5 (7)

Symmetry codes: (i) −x+1, −y, z; (ii) x−1/2, −y+1/2, z; (iii) −x+3/2, y−1/2, z; (iv) −y+1, x, z−1/2; (v) x+1/2, −y+1/2, z−1; (vi) −y+3/2, −x+1/2, z−1/2; (vii) y+1/2, x−1/2, z−1/2; (viii) −y+1/2, −x+3/2, z+1/2; (ix) y−1/2, x−1/2, z+1/2; (x) −x+3/2, y+1/2, z; (xi) x+1/2, −y+1/2, z; (xii) −y, x, z+1/2; (xiii) x−1/2, −y+1/2, z+1; (xiv) −y+1, x, z+1/2; (xv) y, −x+1, z+1/2; (xvi) y+1/2, x−1/2, z+1/2.

argon methylammonium lead iodide (XI)

Crystal data

I3Pb·(CN)·1.337(Ar)	High pressure P = 0.98 GPa
Mr = 673.4	Dx = 4.900 Mg m^−3
Tetragonal, P42bc	Synchrotron radiation, λ = 0.3738 Å
Hall symbol: P 4c -2ab	Cell parameters from 1260 reflections
a = 8.7222 (15) Å	θ = 2.8–13.4°
c = 11.9979 (15) Å	µ = 5.35 mm^−1
V = 912.8 (3) Å^3	T = 293 K
Z = 4	Irregular
F(000) = 1112

Data collection

Abstract diffractometer	84 reflections with I > 3σ(I)
Radiation source: synchrotron	Rint = 0.076
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.4°, θmin = 2.8°
	h = −10→10
1260 measured reflections	k = −10→10
247 independent reflections	l = −15→14

Refinement

Refinement on F	2 constraints
R[F^2 > 2σ(F^2)] = 0.079	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.115	(Δ/σ)max = 0.050
S = 1.82	Δρmax = 2.43 e Å^−3
247 reflections	Δρmin = −2.03 e Å^−3
28 parameters	Absolute structure: 189 of Friedel pairs used in the refinement
1 restraint	Absolute structure parameter: 0.001 (14)

Special details

Experimental. High pressure P=0.98 GPa; Ar PTM

Refinement. No H atoms are included into the model; Twin. C , N and Ar atoms have been refined with isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0	−0.0002 (11)	0.125 (6)
I2	0.765 (6)	0.247 (5)	−0.049 (4)	0.188 (19)
I1	0	0.5	0.747 (4)	0.32 (9)
C1	0.5	0.5	0.293 (6)	0.01 (3)*
N1	0.5	0.5	0.393 (6)	0.01 (3)*
Ar	0.861 (7)	0.288 (7)	0.204 (5)	0.09 (2)*	0.67 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.283 (17)	0.040 (5)	0.052 (5)	−0.103 (6)	0	0
I2	0.23 (5)	0.16 (3)	0.165 (19)	−0.12 (3)	0.14 (3)	−0.10 (3)
I1	0.25 (9)	0.70 (11)	0.025 (13)	−0.04 (5)	0	0

Geometric parameters (Å, º)

Pb1—I2	3.21 (3)	I2—N1^vi	3.04 (4)
Pb1—I2^i	3.21 (3)	I2—Ar	3.15 (6)
Pb1—I2^ii	3.07 (3)	I2—Ar^vii	3.13 (6)
Pb1—I2^iii	3.07 (3)	I1—Ar^viii	2.27 (5)
Pb1—I1^iv	2.96 (3)	I1—Ar^ix	2.27 (5)
Pb1—I1^v	3.04 (3)	C1—N1	1.21 (8)
Pb1—Ar^ii	3.32 (5)	C1—Ar^ii	2.98 (6)
Pb1—Ar^iii	3.32 (5)	C1—Ar^x	2.98 (6)
I2—N1^iv	3.27 (4)
I2—Pb1—I2^i	158.8 (9)	Pb1^xi—I2—Ar^vii	85.8 (13)
I2—Pb1—I2^ii	87.9 (9)	N1^iv—I2—N1^vi	155.2 (18)
I2—Pb1—I2^iii	88.1 (9)	N1^iv—I2—Ar	107.8 (16)
I2—Pb1—I1^iv	100.6 (6)	N1^iv—I2—Ar^vii	68.4 (15)
I2—Pb1—I1^v	79.4 (6)	N1^vi—I2—Ar	96.7 (17)
I2—Pb1—Ar^ii	91.5 (11)	N1^vi—I2—Ar^vii	88.4 (16)
I2—Pb1—Ar^iii	104.1 (11)	Ar—I2—Ar^vii	150.2 (18)
I2^i—Pb1—I2^ii	88.1 (9)	Pb1^xii—I1—Pb1^xiii	180.0 (5)
I2^i—Pb1—I2^iii	87.9 (9)	Pb1^xii—I1—Ar^viii	76.8 (15)
I2^i—Pb1—I1^iv	100.6 (6)	Pb1^xii—I1—Ar^ix	76.8 (15)
I2^i—Pb1—I1^v	79.4 (6)	Pb1^xiii—I1—Ar^viii	103.2 (15)
I2^i—Pb1—Ar^ii	104.1 (11)	Pb1^xiii—I1—Ar^ix	103.2 (15)
I2^i—Pb1—Ar^iii	91.5 (11)	Ar^viii—I1—Ar^ix	154 (2)
I2^ii—Pb1—I2^iii	157.8 (9)	N1—C1—Ar^ii	111.5 (14)
I2^ii—Pb1—I1^iv	101.1 (6)	N1—C1—Ar^x	111.5 (14)
I2^ii—Pb1—I1^v	78.9 (6)	Ar^ii—C1—Ar^x	137 (2)
I2^ii—Pb1—Ar^ii	58.8 (11)	I2^xiv—N1—I2^xv	156 (2)
I2^ii—Pb1—Ar^iii	143.2 (11)	I2^xiv—N1—I2^viii	87.5 (10)
I2^iii—Pb1—I1^iv	101.1 (6)	I2^xiv—N1—I2^xvi	87.3 (10)
I2^iii—Pb1—I1^v	78.9 (6)	I2^xiv—N1—C1	101.9 (11)
I2^iii—Pb1—Ar^ii	143.2 (11)	I2^xv—N1—I2^viii	87.3 (10)
I2^iii—Pb1—Ar^iii	58.8 (11)	I2^xv—N1—I2^xvi	87.5 (10)
I1^iv—Pb1—I1^v	180.0 (5)	I2^xv—N1—C1	101.9 (11)
I1^iv—Pb1—Ar^ii	42.9 (9)	I2^viii—N1—I2^xvi	154 (2)
I1^iv—Pb1—Ar^iii	42.9 (9)	I2^viii—N1—C1	102.8 (12)
I1^v—Pb1—Ar^ii	137.1 (9)	I2^xvi—N1—C1	102.8 (12)
I1^v—Pb1—Ar^iii	137.1 (9)	Pb1^xi—Ar—I2	56.7 (11)
Ar^ii—Pb1—Ar^iii	85.8 (13)	Pb1^xi—Ar—I2^xvi	147 (2)
Pb1—I2—Pb1^xi	157.8 (12)	Pb1^xi—Ar—I1^vi	60.3 (14)
Pb1—I2—N1^iv	88.9 (9)	Pb1^xi—Ar—C1^xi	125.6 (18)
Pb1—I2—N1^vi	93.1 (9)	I2—Ar—I2^xvi	146 (2)
Pb1—I2—Ar	94.3 (13)	I2—Ar—I1^vi	116 (2)
Pb1—I2—Ar^vii	114.8 (14)	I2—Ar—C1^xi	112 (2)
Pb1^xi—I2—N1^iv	91.3 (9)	I2^xvi—Ar—I1^vi	89.5 (19)
Pb1^xi—I2—N1^vi	95.9 (10)	I2^xvi—Ar—C1^xi	74.8 (17)
Pb1^xi—I2—Ar	64.5 (12)	I1^vi—Ar—C1^xi	111 (2)

Symmetry codes: (i) −x+1, −y, z; (ii) x−1/2, −y+1/2, z; (iii) −x+3/2, y−1/2, z; (iv) −y+1, x, z−1/2; (v) x+1/2, −y+1/2, z−1; (vi) −y+3/2, −x+1/2, z−1/2; (vii) y+1/2, x−1/2, z−1/2; (viii) −y+1/2, −x+3/2, z+1/2; (ix) y−1/2, x−1/2, z+1/2; (x) −x+3/2, y+1/2, z; (xi) x+1/2, −y+1/2, z; (xii) −y, x, z+1/2; (xiii) x−1/2, −y+1/2, z+1; (xiv) −y+1, x, z+1/2; (xv) y, −x+1, z+1/2; (xvi) y+1/2, x−1/2, z+1/2.

argon methylammonium lead iodide (XII)

Crystal data

I3Pb·(CN)·1.4(Ar)	F(000) = 2234
Mr = 675.9	High pressure P = 1.34 GPa
Orthorhombic, Immm	Dx = 5.008 Mg m^−3
Hall symbol: -I 2 2	Synchrotron radiation, λ = 0.3738 Å
a = 12.1294 (12) Å	Cell parameters from 772 reflections
b = 12.1415 (12) Å	θ = 2.8–13.5°
c = 12.1734 (15) Å	µ = 5.45 mm^−1
V = 1792.8 (3) Å^3	T = 293 K
Z = 8	Irregular

Data collection

Abstract diffractometer	104 reflections with I > 2.5σ(I)
Radiation source: synchrotron	Rint = 0.121
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.5°, θmin = 2.8°
	h = −14→15
772 measured reflections	k = −4→4
237 independent reflections	l = −15→14

Refinement

Refinement on F	4 restraints
R[F^2 > 2σ(F^2)] = 0.086	0 constraints
wR(F^2) = 0.108	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 1.40	(Δ/σ)max = 0.050
237 reflections	Δρmax = 0.86 e Å^−3
35 parameters	Δρmin = −1.10 e Å^−3

Special details

Experimental. High pressure P = 1.34 GPa; Ar PTM

Refinement. No H atoms are included into the model; Twin. All atoms have been refined with only isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.25	0.25	0.25	0.119 (7)
I1	0	0.247 (2)	0.224 (3)	0.123 (13)
I2	0.273 (5)	0.5	0.1947 (17)	0.21 (3)
I3	0.815 (3)	0.3012 (18)	0.5	0.123 (12)
N1	0	0.5	0	0.001 (1)*
C1	0	0.405057	0	0.001 (1)*	0.5
N2	0	0.5	0.267 (13)	0.001 (1)*	0.5
C2	0	0.5	0.361 (14)	0.001 (1)*	0.5
C3	0	0	0.083 (12)	0.001 (1)*	0.5
N3	0	0	0.183 (12)	0.001 (1)*	0.5
N4	0	0	0.5	0.001 (1)*
C4	0	0	0.596 (3)	0.001 (1)*	0.5
Ar1	0.154 (4)	0.171 (7)	0	0.21 (8)*
Ar2	0	0.21167 (12)	0.5	0.20 (7)*	0.801 (7)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.146 (12)	0.117 (14)	0.092 (9)	−0.072 (10)	0.040 (11)	0.014 (9)
I1	0.001 (3)	0.11 (2)	0.26 (3)	0	0	0.08 (3)
I2	0.51 (8)	0.052 (12)	0.069 (12)	0	0.181 (19)	0
I3	0.22 (3)	0.091 (15)	0.061 (11)	−0.06 (2)	0	0

Geometric parameters (Å, º)

Pb1—I1	3.049 (4)	N2—C2	1.1 (2)
Pb1—I1^i	3.049 (4)	C3—C3^ix	2.0 (2)
Pb1—I2	3.122 (7)	C3—N3	1.2 (2)
Pb1—I2^ii	3.122 (7)	C3—N3^ix	3.2 (2)
Pb1—I3^iii	3.204 (10)	C3—Ar1	2.97 (9)
Pb1—I3^iv	3.204 (10)	C3—Ar1^x	2.97 (9)
I1—N2	3.11 (4)	C3—Ar1^ix	2.97 (9)
I1—N3	3.04 (4)	C3—Ar1^xi	2.97 (9)
I2—N3^v	3.13 (9)	N3—C4^xii	2.70 (15)
I2—C4^vi	3.00 (5)	N4—C4	1.16 (4)
I3—Ar1^i	1.98 (6)	N4—C4^xii	1.16 (4)
I3—Ar2^vii	2.50 (3)	N4—Ar2	2.5700 (15)
N1—C1	1.1528 (2)	N4—Ar2^x	2.5700 (15)
N1—C1^viii	1.1528 (2)	C4—C4^xii	2.33 (6)
N1—N2	3.25 (16)	C4—Ar2	2.821 (17)
N1—N2^ix	3.25 (16)	C4—Ar2^x	2.821 (17)
C1—C1^viii	2.3055 (5)
I1—Pb1—I1^i	180.0 (5)	Ar1^x—C3—Ar1^xi	78 (2)
I1—Pb1—I2	94.5 (11)	Ar1^ix—C3—Ar1^xi	140 (5)
I1—Pb1—I2^ii	85.5 (11)	I1—N3—I1^x	161 (6)
I1—Pb1—I3^iii	81.7 (10)	I1—N3—I2^ii	85.5 (17)
I1—Pb1—I3^iv	98.3 (10)	I1—N3—I2^iv	85.5 (17)
I1^i—Pb1—I2	85.5 (11)	I1—N3—C3	100 (3)
I1^i—Pb1—I2^ii	94.5 (11)	I1—N3—C3^ix	100 (3)
I1^i—Pb1—I3^iii	98.3 (10)	I1—N3—C4^xii	80 (3)
I1^i—Pb1—I3^iv	81.7 (10)	I1^x—N3—I2^ii	85.5 (17)
I2—Pb1—I2^ii	180.0 (5)	I1^x—N3—I2^iv	85.5 (17)
I2—Pb1—I3^iii	92.2 (6)	I1^x—N3—C3	100 (3)
I2—Pb1—I3^iv	87.8 (6)	I1^x—N3—C3^ix	100 (3)
I2^ii—Pb1—I3^iii	87.8 (6)	I1^x—N3—C4^xii	80 (3)
I2^ii—Pb1—I3^iv	92.2 (6)	I2^ii—N3—I2^iv	123 (5)
I3^iii—Pb1—I3^iv	180.0 (5)	I2^ii—N3—C3	118 (2)
Pb1—I1—Pb1^iv	168.1 (15)	I2^ii—N3—C3^ix	118 (2)
Pb1—I1—N2	88.4 (7)	I2^ii—N3—C4^xii	62 (2)
Pb1—I1—N3	91.6 (6)	I2^iv—N3—C3	118 (2)
Pb1^iv—I1—N2	88.4 (7)	I2^iv—N3—C3^ix	118 (2)
Pb1^iv—I1—N3	91.6 (6)	I2^iv—N3—C4^xii	62 (2)
N2—I1—N3	180.0 (5)	C3—N3—C4^xii	180.0 (5)
Pb1—I2—Pb1^v	152.9 (10)	C3^ix—N3—C4^xii	180.0 (5)
Pb1—I2—N3^v	88.7 (10)	C4—N4—C4^xii	180.0 (5)
Pb1—I2—C4^vi	99.8 (10)	C4—N4—Ar2	90
Pb1^v—I2—N3^v	88.7 (10)	C4—N4—Ar2^x	90
Pb1^v—I2—C4^vi	99.8 (10)	C4^xii—N4—Ar2	90
N3^v—I2—C4^vi	52 (3)	C4^xii—N4—Ar2^x	90
Pb1^iii—I3—Pb1^i	143.5 (11)	Ar2—N4—Ar2^x	180.0 (5)
Pb1^iii—I3—Ar1^i	78.0 (9)	I2^xiii—C4—I2^xiv	132.6 (16)
Pb1^iii—I3—Ar2^vii	97.8 (6)	I2^xiii—C4—N3^xii	66.3 (9)
Pb1^i—I3—Ar1^i	78.0 (9)	I2^xiii—C4—N4	113.7 (9)
Pb1^i—I3—Ar2^vii	97.8 (6)	I2^xiii—C4—C4^xii	113.7 (9)
Ar1^i—I3—Ar2^vii	164 (3)	I2^xiii—C4—Ar2	99.5 (2)
C1—N1—C1^viii	180.0 (5)	I2^xiii—C4—Ar2^x	99.5 (2)
C1—N1—N2	90	I2^xiv—C4—N3^xii	66.3 (9)
C1—N1—N2^ix	90	I2^xiv—C4—N4	113.7 (9)
C1^viii—N1—N2	90	I2^xiv—C4—C4^xii	113.7 (9)
C1^viii—N1—N2^ix	90	I2^xiv—C4—Ar2	99.5 (2)
N2—N1—N2^ix	180.0 (5)	I2^xiv—C4—Ar2^x	99.5 (2)
I1—N2—I1^viii	161 (6)	N3^xii—C4—N4	180.0 (5)
I1—N2—N1	80 (3)	N3^xii—C4—C4^xii	180.0 (5)
I1—N2—C2	100 (3)	N3^xii—C4—Ar2	114.4 (8)
I1^viii—N2—N1	80 (3)	N3^xii—C4—Ar2^x	114.4 (8)
I1^viii—N2—C2	100 (3)	N4—C4—Ar2	65.6 (8)
N1—N2—C2	180.0 (5)	N4—C4—Ar2^x	65.6 (8)
N3—C3—N3^ix	180.0 (5)	C4^xii—C4—Ar2	65.6 (8)
N3—C3—Ar1	110 (3)	C4^xii—C4—Ar2^x	65.6 (8)
N3—C3—Ar1^x	110 (3)	Ar2—C4—Ar2^x	131.3 (15)
N3—C3—Ar1^ix	110 (3)	I3^iv—Ar1—C3	138 (3)
N3—C3—Ar1^xi	110 (3)	I3^iv—Ar1—C3^ix	138 (3)
N3^ix—C3—Ar1	70 (3)	C3—Ar1—C3^ix	40 (4)
N3^ix—C3—Ar1^x	70 (3)	I3^xv—Ar2—I3^iii	128.3 (8)
N3^ix—C3—Ar1^ix	70 (3)	I3^xv—Ar2—N4	115.8 (6)
N3^ix—C3—Ar1^xi	70 (3)	I3^xv—Ar2—C4	113.4 (5)
Ar1—C3—Ar1^x	140 (5)	I3^xv—Ar2—C4^xii	113.4 (5)
Ar1—C3—Ar1^ix	78 (2)	I3^iii—Ar2—N4	115.8 (6)
Ar1—C3—Ar1^xi	89 (3)	I3^iii—Ar2—C4	113.4 (5)
Ar1^x—C3—Ar1^ix	89 (3)	I3^iii—Ar2—C4^xii	113.4 (5)

Symmetry codes: (i) x+1/2, −y+1/2, −z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) −x+1, y, −z+1; (iv) x−1/2, −y+1/2, −z+1/2; (v) −x+1/2, y+1/2, −z+1/2; (vi) x+1/2, y+1/2, z−1/2; (vii) x+1, y, z; (viii) −x, −y+1, z; (ix) −x, y, −z; (x) −x, −y, z; (xi) x, −y, −z; (xii) −x, y, −z+1; (xiii) x−1/2, y−1/2, z+1/2; (xiv) −x+1/2, −y+1/2, z+1/2; (xv) x−1, y, z.

argon methylammonium lead iodide (XIII)

Crystal data

I3Pb·(CN)·1.781(Ar)	F(000) = 2292
Mr = 692.1	High pressure P = 2.1 GPa
Orthorhombic, Immm	Dx = 5.294 Mg m^−3
Hall symbol: -I 2 2	Synchrotron radiation, λ = 0.3738 Å
a = 12.0192 (10) Å	Cell parameters from 799 reflections
b = 12.0195 (10) Å	θ = 2.8–13.5°
c = 12.0213 (10) Å	µ = 5.65 mm^−1
V = 1736.7 (3) Å^3	T = 293 K
Z = 8	Irregular

Data collection

Abstract diffractometer	78 reflections with I > 2.5σ(I)
Radiation source: synchrotron	Rint = 0.116
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.5°, θmin = 2.8°
	h = −14→14
799 measured reflections	k = −4→4
248 independent reflections	l = −14→14

Refinement

Refinement on F	4 restraints
R[F^2 > 2σ(F^2)] = 0.084	13 constraints
wR(F^2) = 0.124	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 1.01	(Δ/σ)max = 0.047
248 reflections	Δρmax = 2.16 e Å^−3
36 parameters	Δρmin = −1.90 e Å^−3

Special details

Experimental. High pressure P = 2.1 GPa Ar PTM

Refinement. No H atoms are included into the model; Twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.25	0.25	0.25	0.085 (6)
I1	0	0.219 (4)	0.248 (6)	0.24 (3)
I2	0.235 (3)	0.5	0.182 (3)	0.109 (12)
I3	0.812 (2)	0.3029 (14)	0.5	0.105 (13)
C1	0	0.5	0	0.137 (9)*
Ar3	0	0.5	0.338 (4)	0.001 (1)*	0.724 (19)
N2	0.125 (3)	0.5	0.5	0.001 (1)*	0.5
C3	0	0	0.0499 (8)	0.001 (1)*	0.5
N3	0	0	0.0499 (8)	0.001 (1)*	0.5
Ar1	0.160 (2)	0.1570 (16)	0	0.001 (1)*
Ar2	0	0.211 (3)	0.5	0.001 (1)*	0.837 (19)
C2	0	0.5	0.5	0.001 (1)*
N1	0.10 (9)	0.5	0	0.137 (9)*	0.5
N4	−0.0624 (8)	0	0.5	0.187 (9)*	0.5
C4	−0.0624 (8)	0	0.5	0.187 (9)*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.098 (13)	0.085 (8)	0.072 (7)	−0.018 (6)	0.057 (9)	−0.009 (5)
I1	0.07 (2)	0.21 (3)	0.45 (9)	0	0	−0.24 (5)
I2	0.09 (2)	0.102 (16)	0.14 (3)	0	0.03 (3)	0
I3	0.25 (4)	0.054 (9)	0.013 (6)	−0.046 (15)	0	0

Geometric parameters (Å, º)

Pb1—I1	3.028 (5)	Ar3—N2	2.46 (4)
Pb1—I1^i	3.028 (5)	Ar3—N2^viii	2.46 (4)
Pb1—I2	3.118 (9)	Ar3—C2	1.95 (5)
Pb1—I2^ii	3.118 (9)	N2—N2^viii	3.01 (4)
Pb1—I3^iii	3.160 (7)	N2—Ar1^ix	3.20 (3)
Pb1—I3^iv	3.160 (7)	N2—Ar1^x	3.20 (3)
I1—Ar2	3.03 (7)	N2—C2	1.51 (3)
I2—N1	2.7 (7)	C3—N3^xi	1.200 (14)
I2—N4^v	3.27 (3)	C3—Ar1	2.76 (2)
I2—C4^v	3.27 (3)	C3—Ar1^xii	2.76 (2)
I3—N2^vi	2.49 (2)	C3—Ar1^xi	2.76 (2)
I3—Ar1^i	1.89 (3)	C3—Ar1^xiii	2.76 (2)
I3—Ar2^vii	2.52 (3)	Ar2—C4	2.65 (3)
I3—C2^vii	3.28 (2)	Ar2—C4^xii	2.65 (3)
C1—N1	1.2 (11)	N1—N1^viii	2.4 (16)
C1—N1^viii	1.2 (11)	N4—C4^xii	1.500 (14)
I1—Pb1—I1^i	180.0 (5)	I3^iv—Ar1—N3^xi	148.0 (10)
I1—Pb1—I2	93.4 (10)	N2^xv—Ar1—C3	99.1 (7)
I1—Pb1—I2^ii	86.6 (10)	N2^xv—Ar1—C3^xi	99.1 (7)
I1—Pb1—I3^iii	78.5 (13)	N2^xv—Ar1—N3	99.1 (7)
I1—Pb1—I3^iv	101.5 (13)	N2^xv—Ar1—N3^xi	99.1 (7)
I1^i—Pb1—I2	86.6 (10)	I1—Ar2—I1^xiv	176.5 (18)
I1^i—Pb1—I2^ii	93.4 (10)	I1—Ar2—I3^xvi	89.2 (5)
I1^i—Pb1—I3^iii	101.5 (13)	I1—Ar2—I3^iii	89.2 (5)
I1^i—Pb1—I3^iv	78.5 (13)	I1—Ar2—N4	91.7 (10)
I2—Pb1—I2^ii	180.0 (5)	I1—Ar2—N4^xii	91.7 (10)
I2—Pb1—I3^iii	92.3 (7)	I1^xiv—Ar2—I3^xvi	89.2 (5)
I2—Pb1—I3^iv	87.7 (7)	I1^xiv—Ar2—I3^iii	89.2 (5)
I2^ii—Pb1—I3^iii	87.7 (7)	I1^xiv—Ar2—N4	91.7 (10)
I2^ii—Pb1—I3^iv	92.3 (7)	I1^xiv—Ar2—N4^xii	91.7 (10)
I3^iii—Pb1—I3^iv	180.0 (5)	I1^xiv—Ar2—C4	91.7 (10)
Pb1—I1—Pb1^iv	165.9 (16)	I1^xiv—Ar2—C4^xii	91.7 (10)
Pb1—I1—Ar2	89.7 (13)	I3^xvi—Ar2—I3^iii	128.2 (16)
Pb1^iv—I1—Ar2	89.7 (13)	I3^xvi—Ar2—N4	99.5 (7)
Pb1—I2—Pb1^x	149.1 (12)	I3^xvi—Ar2—N4^xii	132.3 (11)
Pb1—I2—N1	104 (2)	I3^xvi—Ar2—C4	99.5 (7)
Pb1—I2—N4^v	97.6 (6)	I3^xvi—Ar2—C4^xii	132.3 (11)
Pb1^x—I2—N1	104 (2)	I3^iii—Ar2—N4	132.3 (11)
Pb1^x—I2—N4^v	97.6 (6)	I3^iii—Ar2—N4^xii	99.5 (7)
N1—I2—N4^v	85 (19)	I3^iii—Ar2—C4	132.3 (11)
Pb1^iii—I3—Pb1^i	144.0 (7)	I3^iii—Ar2—C4^xii	99.5 (7)
Pb1^iii—I3—N2^vi	105.3 (3)	N4—Ar2—N4^xii	32.9 (5)
Pb1^iii—I3—Ar1^i	79.9 (5)	I3^xvi—C2—I3^vi	180.0 (5)
Pb1^iii—I3—Ar2^vii	97.1 (4)	I3^xvi—C2—I3^iii	87.4 (5)
Pb1^iii—I3—C2^vii	107.9 (4)	I3^xvi—C2—I3^xvii	92.6 (5)
Pb1^i—I3—N2^vi	105.3 (3)	I3^xvi—C2—Ar3	90
Pb1^i—I3—Ar1^i	79.9 (5)	I3^xvi—C2—Ar3^xiv	90
Pb1^i—I3—Ar2^vii	97.1 (4)	I3^xvi—C2—N2	133.7 (4)
Pb1^i—I3—C2^vii	107.9 (4)	I3^vi—C2—I3^iii	92.6 (5)
N2^vi—I3—Ar1^i	92.9 (11)	I3^vi—C2—I3^xvii	87.4 (5)
N2^vi—I3—Ar2^vii	98.2 (13)	I3^vi—C2—Ar3	90
Ar1^i—I3—Ar2^vii	168.9 (13)	I3^vi—C2—Ar3^xiv	90
Ar1^i—I3—C2^vii	118.9 (9)	I3^vi—C2—N2^viii	133.7 (4)
Ar2^vii—I3—C2^vii	72.2 (9)	I3^iii—C2—I3^xvii	180.0 (5)
N1—C1—N1^viii	180.0 (5)	I3^iii—C2—Ar3	90
N2—Ar3—N2^viii	75.5 (16)	I3^iii—C2—Ar3^xiv	90
I3^vi—N2—I3^iii	144.5 (15)	I3^iii—C2—N2^viii	133.7 (4)
I3^vi—N2—Ar3	100.7 (4)	I3^xvii—C2—Ar3	90
I3^vi—N2—Ar3^xiv	100.7 (4)	I3^xvii—C2—Ar3^xiv	90
I3^vi—N2—N2^viii	107.7 (9)	I3^xvii—C2—N2	133.7 (4)
I3^vi—N2—Ar1^ix	108.4 (12)	Ar3—C2—Ar3^xiv	180.0 (5)
I3^vi—N2—C2	107.7 (9)	Ar3—C2—N2	90
I3^iii—N2—Ar3	100.7 (4)	Ar3—C2—N2^viii	90
I3^iii—N2—Ar3^xiv	100.7 (4)	Ar3^xiv—C2—N2	90
I3^iii—N2—N2^viii	107.7 (9)	Ar3^xiv—C2—N2^viii	90
I3^iii—N2—Ar1^x	108.4 (12)	N2—C2—N2^viii	180.0 (5)
I3^iii—N2—C2	107.7 (9)	I2—N1—I2^xviii	110 (40)
Ar3—N2—Ar3^xiv	104.5 (15)	I2—N1—C1	127 (19)
Ar3—N2—Ar1^ix	119.6 (6)	I2^xviii—N1—C1	127 (19)
Ar3—N2—Ar1^x	119.6 (6)	I2^xix—N4—I2^iv	84.1 (8)
Ar3^xiv—N2—N2^viii	52.3 (9)	I2^xix—N4—Ar2	102.1 (2)
Ar3^xiv—N2—Ar1^ix	119.6 (6)	I2^xix—N4—Ar2^xii	102.1 (2)
Ar3^xiv—N2—Ar1^x	119.6 (6)	I2^xix—N4—C4^xii	138.0 (6)
N2^viii—N2—Ar1^ix	143.9 (5)	I2^iv—N4—Ar2	102.1 (2)
N2^viii—N2—Ar1^x	143.9 (5)	I2^iv—N4—Ar2^xii	102.1 (2)
Ar1^ix—N2—Ar1^x	72.3 (8)	I2^iv—N4—N4^xii	138.0 (6)
Ar1^ix—N2—C2	143.9 (5)	I2^iv—N4—C4^xii	138.0 (6)
Ar1^x—N2—C2	143.9 (5)	Ar2—N4—Ar2^xii	147.1 (5)
N3^xi—C3—Ar1	77.4 (2)	I2^xix—C4—I2^iv	84.1 (8)
Ar1—C3—Ar1^xii	154.9 (4)	I2^xix—C4—Ar2	102.1 (2)
Ar1—C3—Ar1^xi	88.3 (6)	I2^xix—C4—Ar2^xii	102.1 (2)
Ar1—C3—Ar1^xiii	86.3 (6)	I2^xix—C4—N4^xii	138.0 (6)
Ar1^xii—C3—Ar1^xi	86.3 (6)	I2^xix—C4—C4^xii	138.0 (6)
Ar1^xii—C3—Ar1^xiii	88.3 (6)	I2^iv—C4—Ar2	102.1 (2)
Ar1^xi—C3—Ar1^xiii	154.9 (4)	I2^iv—C4—Ar2^xii	102.1 (2)
C3^xi—N3—Ar1	77.4 (2)	I2^iv—C4—N4^xii	138.0 (6)
I3^iv—Ar1—C3	148.0 (10)	I2^iv—C4—C4^xii	138.0 (6)
I3^iv—Ar1—C3^xi	148.0 (10)	Ar2—C4—Ar2^xii	147.1 (5)
I3^iv—Ar1—N3	148.0 (10)

Symmetry codes: (i) x+1/2, −y+1/2, −z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) −x+1, y, −z+1; (iv) x−1/2, −y+1/2, −z+1/2; (v) x+1/2, y+1/2, z−1/2; (vi) −x+1, −y+1, z; (vii) x+1, y, z; (viii) −x, −y+1, z; (ix) −x+1/2, −y+1/2, z+1/2; (x) −x+1/2, y+1/2, −z+1/2; (xi) −x, y, −z; (xii) −x, −y, z; (xiii) x, −y, −z; (xiv) −x, y, −z+1; (xv) −x+1/2, −y+1/2, z−1/2; (xvi) x−1, y, z; (xvii) x−1, −y+1, −z+1; (xviii) x, −y+1, −z; (xix) x−1/2, y−1/2, z+1/2.

argon methylammonium lead iodide (XIV)

Crystal data

I3Pb·(CN)·1.75(Ar)	F(000) = 2284
Mr = 689.9	High pressure P = 2.39 GPa
Orthorhombic, Immm	Dx = 5.389 Mg m^−3
Hall symbol: -I 2 2	Synchrotron radiation, λ = 0.3738 Å
a = 11.900 (1) Å	Cell parameters from 714 reflections
b = 11.990 (1) Å	θ = 2.8–13.5°
c = 11.920 (1) Å	µ = 5.77 mm^−1
V = 1700.8 (2) Å^3	T = 293 K
Z = 8	Irregular

Data collection

Abstract diffractometer	46 reflections with I > 2.5σ(I)
Radiation source: synchrotron	Rint = 0.124
Absorption correction: empirical (using intensity measurements) CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	θmax = 13.5°, θmin = 2.8°
	h = −14→14
714 measured reflections	k = −4→4
247 independent reflections	l = −14→14

Refinement

Refinement on F	11 constraints
R[F^2 > 2σ(F^2)] = 0.066	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.144	(Δ/σ)max = 0.048
S = 1.08	Δρmax = 1.42 e Å^−3
247 reflections	Δρmin = −1.32 e Å^−3
36 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
4 restraints	Extinction coefficient: 3700 (1300)

Special details

Experimental. High pressure P = 2.39 GPa Ar PTM

Refinement. No H atoms are included into the model; Twin. All atoms have been refined with only isotropic ADP. This is due to the limited number of reflections obtained in the high-pressure experiment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.25	0.25	0.25	0.216 (14)
I1	0	0.203 (6)	0.207 (12)	0.50 (11)
I2	0.256 (2)	0.5	0.218 (3)	0.121 (13)
I3	0.8166 (19)	0.313 (3)	0.5	0.157 (18)
C1	0	0.5	0	0.001 (1)*
N1	0.124 (5)	0.5	0	0.001 (1)*	0.5
Ar3	0	0.5	0.3573 (8)	0.001 (1)*
N2	0.097 (3)	0.5	0.5	0.028 (11)*	0.5
C3	0	0	0	0.001 (1)*
N3	0	0	0.100 (3)	0.001 (1)*	0.5
Ar1	0.1690 (14)	0.1577 (18)	0	0.001 (1)*
N4	0	0	0.5	0.001 (1)*
C4	0	0	0.597 (3)	0.001 (1)*	0.5
C2	0	0.5	0.5	0.028 (11)*
Ar2	0.3582 (16)	0.5	0	0.001 (1)*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.213 (19)	0.27 (3)	0.17 (2)	0.01 (2)	0.05 (2)	−0.04 (2)
I1	0.51 (18)	0.22 (6)	0.8 (3)	0	0	−0.21 (10)
I2	0.126 (17)	0.053 (8)	0.18 (3)	0	0.04 (2)	0
I3	0.099 (17)	0.19 (3)	0.18 (4)	0.01 (2)	0	0

Geometric parameters (Å, º)

Pb1—I1	3.07 (3)	Ar3—N2^ix	2.06 (2)
Pb1—I1^i	3.07 (3)	N2—N2^ix	2.31 (5)
Pb1—I2	3.023 (5)	N2—C2	1.15 (3)
Pb1—I2^ii	3.023 (5)	C3—N3	1.19 (3)
Pb1—I3^iii	3.175 (10)	C3—N3^v	1.19 (3)
Pb1—I3^iv	3.175 (10)	C3—Ar1	2.760 (19)
I1—N3	2.74 (9)	C3—Ar1^x	2.760 (19)
I1—Ar1	3.23 (11)	C3—Ar1^v	2.760 (19)
I1—Ar1^v	3.23 (11)	C3—Ar1^xi	2.760 (19)
I2—N1	3.03 (5)	N3—N3^v	2.39 (5)
I2—C4^vi	3.24 (3)	N3—Ar1	3.01 (2)
I2—Ar2	2.87 (4)	N3—Ar1^x	3.01 (2)
I3—N2^vii	2.47 (4)	N3—Ar1^v	3.01 (2)
I3—Ar1^i	1.79 (3)	N3—Ar1^xi	3.01 (2)
I3—C2^viii	3.13 (3)	N4—C4	1.15 (3)
C1—N1	1.48 (6)	N4—C4^xii	1.15 (3)
C1—N1^ix	1.48 (6)	C4—C4^xii	2.30 (5)
N1—N1^ix	2.96 (9)	C4—Ar2^xiii	2.04 (2)
N1—Ar2	2.78 (6)	C4—Ar2^xiv	2.04 (2)
Ar3—N2	2.06 (2)
I1—Pb1—I1^i	180.0 (5)	I1—N3—C3	118 (3)
I1—Pb1—I2	100.7 (14)	I1—N3—N3^v	118 (3)
I1—Pb1—I2^ii	79.3 (14)	I1—N3—Ar1	68 (2)
I1—Pb1—I3^iii	88 (3)	I1—N3—Ar1^x	137.8 (4)
I1—Pb1—I3^iv	92 (3)	I1—N3—Ar1^v	68 (2)
I1^i—Pb1—I2	79.3 (14)	I1—N3—Ar1^xi	137.8 (4)
I1^i—Pb1—I2^ii	100.7 (14)	I1^x—N3—C3	118 (3)
I1^i—Pb1—I3^iii	92 (3)	I1^x—N3—N3^v	118 (3)
I1^i—Pb1—I3^iv	88 (3)	I1^x—N3—Ar1	137.8 (4)
I2—Pb1—I2^ii	180.0 (5)	I1^x—N3—Ar1^x	68 (2)
I2—Pb1—I3^iii	83.6 (9)	I1^x—N3—Ar1^v	137.8 (4)
I2—Pb1—I3^iv	96.4 (9)	I1^x—N3—Ar1^xi	68 (2)
I2^ii—Pb1—I3^iii	96.4 (9)	Ar1—N3—Ar1^x	133.2 (11)
I2^ii—Pb1—I3^iv	83.6 (9)	Ar1—N3—Ar1^v	83.9 (6)
I3^iii—Pb1—I3^iv	180.0 (5)	Ar1^x—N3—Ar1^xi	83.9 (6)
Pb1—I1—Pb1^iv	151 (4)	Ar1^v—N3—Ar1^xi	133.2 (11)
Pb1—I1—N3	104.0 (16)	I1—Ar1—I1^v	100 (2)
Pb1—I1—Ar1	63.6 (11)	I1—Ar1—I3^iv	125.3 (16)
Pb1—I1—Ar1^v	140 (4)	I1—Ar1—N3^v	89.5 (15)
Pb1^iv—I1—N3	104.0 (16)	I1^v—Ar1—I3^iv	125.3 (16)
Pb1^iv—I1—Ar1	140 (4)	I1^v—Ar1—C3	70.1 (13)
Pb1^iv—I1—Ar1^v	63.6 (11)	I1^v—Ar1—N3	89.5 (15)
N3—I1—Ar1	60 (2)	I3^iv—Ar1—C3	148.1 (15)
N3—I1—Ar1^v	60 (2)	I3^iv—Ar1—N3	141.2 (12)
Ar1—I1—Ar1^v	77 (3)	I3^iv—Ar1—N3^v	141.2 (12)
Pb1—I2—Pb1^xv	165.2 (14)	C4—N4—C4^xii	180.0 (5)
Pb1—I2—N1	95.6 (6)	C4—N4—Ar2^xiii	90
Pb1—I2—C4^vi	94.4 (5)	C4—N4—Ar2^xiv	90
Pb1—I2—Ar2	97.2 (7)	C4^xii—N4—Ar2^xiii	90
Pb1^xv—I2—N1	95.6 (6)	C4^xii—N4—Ar2^xiv	90
Pb1^xv—I2—C4^vi	94.4 (5)	Ar2^xiii—N4—Ar2^xiv	180.0 (5)
Pb1^xv—I2—Ar2	97.2 (7)	I2^xiii—C4—I2^xiv	127.1 (13)
N1—I2—C4^vi	94.7 (15)	I2^xiii—C4—N4	116.4 (8)
Pb1^iii—I3—Pb1^i	139.7 (10)	I2^xiii—C4—C4^xii	116.4 (8)
Pb1^iii—I3—N2^vii	108.7 (6)	I2^xiii—C4—Ar2^xiii	60.8 (7)
Pb1^iii—I3—Ar1^i	78.6 (5)	I2^xiii—C4—Ar2^xiv	172.1 (14)
Pb1^iii—I3—C2^viii	110.2 (5)	I2^xiv—C4—N4	116.4 (8)
Pb1^i—I3—N2^vii	108.7 (6)	I2^xiv—C4—C4^xii	116.4 (8)
Pb1^i—I3—Ar1^i	78.6 (5)	I2^xiv—C4—Ar2^xiii	172.1 (14)
Pb1^i—I3—C2^viii	110.2 (5)	I2^xiv—C4—Ar2^xiv	60.8 (7)
N2^vii—I3—Ar1^i	103.4 (18)	Ar2^xiii—C4—Ar2^xiv	111.4 (15)
Ar1^i—I3—C2^viii	122.9 (17)	I3^xvii—C2—I3^vii	180.0 (5)
N1—C1—N1^ix	180.0 (5)	I3^xvii—C2—I3^iii	88.5 (8)
I2—N1—I2^xvi	118 (2)	I3^xvii—C2—I3^xviii	91.5 (8)
I2—N1—C1	121.1 (11)	I3^xvii—C2—Ar3	90
I2—N1—N1^ix	121.1 (11)	I3^xvii—C2—Ar3^xii	90
I2^xvi—N1—C1	121.1 (11)	I3^xvii—C2—N2	134.2 (5)
I2^xvi—N1—N1^ix	121.1 (11)	I3^vii—C2—I3^iii	91.5 (8)
C1—N1—Ar2	180.0 (5)	I3^vii—C2—I3^xviii	88.5 (8)
N1^ix—N1—Ar2	180.0 (5)	I3^vii—C2—Ar3	90
I3^vii—N2—I3^iii	130.6 (16)	I3^vii—C2—Ar3^xii	90
I3^vii—N2—Ar3	103.5 (3)	I3^vii—C2—N2	45.8 (5)
I3^vii—N2—Ar3^xii	103.5 (3)	I3^vii—C2—N2^ix	134.2 (5)
I3^vii—N2—N2^ix	114.7 (9)	I3^iii—C2—I3^xviii	180.0 (5)
I3^vii—N2—C2	114.7 (9)	I3^iii—C2—Ar3	90
I3^iii—N2—Ar3	103.5 (3)	I3^iii—C2—Ar3^xii	90
I3^iii—N2—Ar3^xii	103.5 (3)	I3^iii—C2—N2	45.8 (5)
I3^iii—N2—N2^ix	114.7 (9)	I3^iii—C2—N2^ix	134.2 (5)
I3^iii—N2—C2	114.7 (9)	I3^xviii—C2—Ar3	90
Ar3—N2—Ar3^xii	111.7 (15)	I3^xviii—C2—Ar3^xii	90
N3—C3—N3^v	180.0 (5)	I3^xviii—C2—N2	134.2 (5)
N3—C3—Ar1	90	Ar3—C2—Ar3^xii	180.0 (5)
N3—C3—Ar1^x	90	Ar3—C2—N2	90
N3—C3—Ar1^v	90	Ar3—C2—N2^ix	90
N3—C3—Ar1^xi	90	Ar3^xii—C2—N2	90
N3^v—C3—Ar1	90	Ar3^xii—C2—N2^ix	90
N3^v—C3—Ar1^x	90	N2—C2—N2^ix	180.0 (5)
N3^v—C3—Ar1^v	90	I2—Ar2—I2^xvi	129.8 (11)
N3^v—C3—Ar1^xi	90	I2—Ar2—N4^vi	115.1 (7)
Ar1—C3—Ar1^x	180.0 (5)	I2—Ar2—C4^vi	80.8 (9)
Ar1—C3—Ar1^v	93.5 (6)	I2—Ar2—C4^xv	149.4 (11)
Ar1—C3—Ar1^xi	86.5 (6)	I2^xvi—Ar2—N4^vi	115.1 (7)
Ar1^x—C3—Ar1^v	86.5 (6)	I2^xvi—Ar2—C4^vi	149.4 (11)
Ar1^x—C3—Ar1^xi	93.5 (6)	N1—Ar2—N4^vi	180.0 (5)
Ar1^v—C3—Ar1^xi	180.0 (5)	N1—Ar2—C4^vi	145.7 (8)
I1—N3—I1^x	125 (4)	N1—Ar2—C4^xv	145.7 (8)

Symmetry codes: (i) x+1/2, −y+1/2, −z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) −x+1, y, −z+1; (iv) x−1/2, −y+1/2, −z+1/2; (v) −x, y, −z; (vi) x+1/2, y+1/2, z−1/2; (vii) −x+1, −y+1, z; (viii) x+1, y, z; (ix) −x, −y+1, z; (x) −x, −y, z; (xi) x, −y, −z; (xii) −x, y, −z+1; (xiii) x−1/2, y−1/2, z+1/2; (xiv) −x+1/2, −y+1/2, z+1/2; (xv) −x+1/2, y+1/2, −z+1/2; (xvi) x, −y+1, −z; (xvii) x−1, y, z; (xviii) x−1, −y+1, −z+1.