Crystal structures of two new high-pressure oxynitrides with composition SnGe₄N₄O₄, from single-crystal electron diffraction

SnGe₄N₄O₄ was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large-volume press. Powder X-ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X-ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe₄N₄O₄ were detected and investigated using automated diffraction tomography (ADT), a three-dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P6₃mc, exhibiting a nolanite-type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe₄N₄O₄ could be found together with the nolanite-type SnGe₄N₄O₄. The structure of this polymorph was solved as well using ADT.

1. Introduction

Germanium and tin are Group 14 elements, capable of forming nitrides and oxynitrides (Bhat et al., 2020; Jorgensen et al., 1979; Labbe & Billy, 1977) with remarkable thermomechanical and optoelectronic properties. Spinel-type germanium and tin nitrides were synthesized long ago (Serghiou et al., 1999; Scotti et al., 1999). Their solid solutions are predicted to form wide direct bandgap semiconductors (Boyko et al., 2013, 2010). Sinoite-type germanium oxynitride Ge₂N₂O has been reported with orthorhombic symmetry (Labbe & Billy, 1977). Tin oxynitride Sn₂N₂O has been found to form a Rh₂S₃-type structure in space group Pbcn, synthesized at high-pressure high-temperature (HP-HT) conditions (Bhat et al., 2020).

GeO₂ and SnO₂ crystallize in the rutile structure type (Haines & Léger, 1997; Shiraki et al., 2003) at ambient conditions and show the same structure types under high pressure. No solid solutions of these compounds are known. Only a limited maximum solubility of 4 mol% GeO₂ in rutile-type SnO₂ at 1250°C has been reported (Watanabe et al., 1983). Mixed GeSn nitrides or oxynitrides are unreactive at ambient conditions and have not been reported up to now, nor are there any computational studies on mixed GeSn oxynitride compounds to the best of our knowledge. This can be explained by Goldschmidt's ninth rule, which postulates that isomorphic substitution between different ions is only possible if the difference in ionic radii is less than 15% of the smaller ion (Goldschmidt, 1926). For Ge and Sn this difference is 30% [taking the ionic radii for octahedral coordination from Shannon, (1976)].

In the case of alloys, bulk Ge–Sn solutions with diamond structure were synthesized at HP-HT conditions by Serghiou et al. (2021). This particularly highlights the high-pressure requirement for the compatibility of Ge and Sn.

Here we report for the first time a GeSn oxynitride, SnGe₄N₄O₄, with a nolanite-type crystal structure and a rhombohedral polytype. Nolanite is an oxide mineral with a hexagonal crystal structure, space group P6₃mc and composition (V, Fe, Ti, Al)₅O₇OH (Gatehouse et al., 1983; Hanson, 1958). Other minerals with a nolanite-type structure have also been described, e.g. akdalaite (= thodite) Al₅O₇OH (Yamaguchi et al., 1969) or rinmanite (Sb, Zn, Mn, Mg)₂(Fe,Mg)₃O₇OH (Holtstam et al., 2001). The crystal chemistry of nolanite-type molybdates A₂Mo₃O₈ has been investigated in detail for a wide range of metals, with A = Mg, Mn, Fe, Co, Ni, Zn, Cd by McCarroll et al. (1957) and A = Mg, Co, Zn, Mn by Abe et al. (2010). Hitherto, no nitrides or oxynitrides with nolanite-type structure were reported. In this work, we focus on the novel phase SnGe₄N₄O₄, which was detected in three different HP-HT experiments.

2. Experimental

2.1. Synthesis

HP-HT synthesis experiments were performed using `Aster-15', the large-volume press installed at the P61B beamline of PETRA III (Farla et al., 2022) at DESY, Hamburg. All HP-HT experiments were carried out using the 14 mm or 10 mm MgO (Cr₂O₃-doped) octahedron and 7 mm or 4 mm truncated tungsten carbide (Fujilloy, 32 mm) anvils. Lanthanum chromite was used as a resistive heater material. Actual pressure and temperature exerted on the sample were calculated from the calibrated relationships between oil pressure (bar) and pressure (GPa), and between heating power (W) and temperature (°C). The starting materials were amorphous oxygen-containing Sn–Ge–N precursors, which had been prepared by the polymer-derived ceramic route (Riedel, 2023), inspired by previously established reactions between Sn(NEt₂)₄ or Hf(NEtMe)₄ and condensed NH₃ (Li et al., 2016; Salamat et al., 2013) (Fig. S1). The HP-HT conditions were ∼20 GPa, ∼1500°C (run #HH228, Pt capsule) and ∼16 GPa, ∼1200°C (run #HH266, graphite capsule). In contrast to sample #HH228, the transfer of the precursor material to the HP capsule was performed for sample #HH266 in a glovebox under an inert gas atmosphere to prevent oxygen contamination. In both experiments, a mixture of several different crystalline phases was formed. One of these phases, common to both samples, is the novel oxynitride SnGe₄N₄O₄ described in this work. To confirm the formation and reproducibility of the novel oxynitride phase, a follow-up HP-HT synthesis experiment (run #HH670, 15.6 GPa, ∼1200°C, graphite capsule) was conducted, using a mechanical mixture of Ge₂N₂O and SnO₂ (2:1 molar ratio) as the starting material.

2.2. Synchrotron powder X-ray diffraction

A qualitative phase analysis, including the refinement of the unit-cell parameters, was performed by angle-dispersive powder X-ray diffraction, using synchrotron radiation at the powder diffraction and total scattering beamline P02.1 of PETRA III at DESY (Hamburg, Germany). P02.1 operates at a fixed energy of 60 keV (∼0.207 Å). The samples were recovered chunks from the HP-HT runs. They were mounted in tight-fitting kapton capillaries with diameters of 0.8 mm to 1.2 mm. The samples were always spun during measurement to avoid any texture effect. The diffraction patterns with an angular range of 1° to 16° were recorded in transmission geometry on an area detector.

2.3. TEM, ADT and TEM-EDX

Three-dimensional electron diffraction (3D ED) and energy-dispersive X-ray spectroscopy (EDX) measurements were conducted using a Tecnai F30 ST instrument with an acceleration voltage of 300 kV (wavelength 0.0197 Å) at the University of Mainz. For 3D ED the illumination system was set to μ-STEM mode with a beam diameter of 200 nm (gun lens 8, spot size 6, C2 condenser aperture 10 µm). The high-angle annular dark-field (HAADF) images for crystal tracking were measured with a Fischione detector. The diffraction patterns were acquired in nanobeam electron diffraction (NBED) mode, with additional electron beam precession (semi-angle of 1° and frequency of 100 Hz (Nanomegas Digistar). A single tilt holder with a tilt range of ±70° from Fischione allowed for the acquisition of 3D ED data on a Gatan US4000 4k × 4k 16-bit CCD camera. To control the 3D ED measurement the Fast-ADT module (Plana-Ruiz et al., 2020) was used in sequential mode. An EDAX Si(Li) detector was used to acquire the EDX spectra at a stage tilt of 20°. The EDX spectra were quantified using the Emispec ESVision software.

TEM samples were prepared by crushing the material in an agate mortar, suspending the resulting powder in ethanol and dropping the suspension on copper grids coated with a continuous carbon film.

Reconstruction of the reciprocal space was performed with eADT (Kolb et al., 2019). The reflection files were prepared with PETS2.0 (Palatinus et al., 2019). Crystal structure determination was carried out with SIR2014 (Burla et al., 2015) at 0.8 Å resolution and refinement of the crystal structure was carried out with JANA2020 (Petříček et al., 2014). All reflections with I < 3σ were classified as unobserved. The structure model was first refined using kinematical approximation. The resulting structure model was further refined, taking dynamical scattering into account (Palatinus et al., 2015).

2.4. Density functional theory

Density functional theory (DFT) calculations were performed with the Vienna ab initio simulation package (VASP) (Hohenberg & Kohn, 1964; Kresse & Furthmüller, 1996; Kresse & Hafner, 1993, 1994) using the strongly conserved and appropriately normed (SCAN) functional together with the projector-augmented-wave (PAW) method (Blöchl, 1994; Kresse & Joubert, 1999; Sun et al., 2015). Reported results refer to calculations with a plane wave cut-off energy of 500 eV. The Brillouin zone of the nolanite-type unit cell and all derived structures was sampled using a 6 × 6 × 4 k-point mesh. With the parameters reported above, enthalpy differences between structures are converged to better than 0.01 eV per conventional unit cell and less than 1 meV per atom.

2.5. Atomic resolution scanning transmission electron microscopy

The electron transparent thin TEM sample was prepared by a focused ion beam, using a Helios G5 focused ion beam scanning electron microscope (FIB-SEM) (Thermo Fisher Scientific), at the University of Tokyo. Atomic resolution annular dark-field (ADF) and annular bright-field (ABF) scanning transmission electron microscopy (STEM) images were acquired with a JEOL ARM300CF transmission electron microscope installed at the University of Tokyo. The ARM300CF is equipped with a Delta-type corrector and a cold field-emission gun and was operated with an acceleration voltage of 300 kV. The illumination semi-angle used was 20 mrad, and the collection semi-angles of ADF and ABF detectors were 40–200 mrad and 10–20 mrad, respectively. To suppress the electron beam damage of the sample, a considerably low electron beam current of 3 pA was used. To enhance the signal-to-noise ratio of the images, sequential fast-scanning STEM imaging was performed and 10 frames were averaged after the image alignment with the rigid-body translation algorithm (Ishikawa et al., 2014).

3. Results

Both recovered samples #HH228 and #HH266 were investigated using synchrotron powder X-ray diffraction (PXRD). Depending on the applied HP-HT synthesis conditions, they show mixtures of several crystalline phases. Among them, only one known phase was identified, namely an α-PbO₂-type high-pressure polymorph of SnO₂ (Haines & Léger, 1997) in sample #HH228. Most of the reflections could not be ascribed to any known Sn or Ge-containing phase. Details of the further analysis are given in Section 3.4.

3.1. SEM

According to the synchrotron XRD analysis, sample #HH266 contains a mixture of different phases. To confirm the distribution of these phases, backscattered electron (BSE) imaging and energy-dispersive X-ray spectroscopy (EDX) was performed. Fig. 1(a) shows the BSE SEM image of the surface of sample #HH266. The grain sizes are estimated to be in the range of 0.2 to 2 µm. Oxygen and nitro­gen atoms are uniformly distributed throughout the whole sample. Nevertheless, different Sn to Ge ratios were found for different grains, indicated by red arrows in Fig. 1(b). As indicated by red arrows in Fig. 1, the Ge-enriched grains have a platy morphology, which may hint at a unique symmetry axis. To directly image the atomic structure of the germanium-enriched grains, the grain marked by the white rectangle in Fig. 1(b) was prepared by FIB milling and observed by atomic resolution STEM imaging. This will be discussed in Section 3.7.

Figure 1 Simultaneously acquired: (a) BSE SEM image of the recovered sample #HH266, and EDX mapping of (b) Ge-L edge and (c) Sn-L edge. White scale bar = 2.5 µm. Red arrows indicate Ge-enriched grains. The white rectangle indicates the position of FIB sampling.

3.2. TEM-EDX

Both HP-HT products were well crystallized, with a grain size of several hundred nanometres. The SnGe₄N₄O₄ phase, which is the focus of this work, could be distinguished from other phases by EDX measurements in both the TEM and SEM. In both HP-HT samples, single crystals of a phase with a very prominent Ge peak and a much smaller additional Sn peak could be identified. More detailed EDX spectra of the single crystals were taken with higher dose to confirm the presence of both N and O, indicating that the crystals are oxynitrides. A typical EDX spectrum is shown in Fig. 2 (additional spectra are shown in Figs. S5 and S6).

Figure 2 EDX spectrum up to 12 kV of the novel Ge-rich phase from #HH228. C, Cu and Si peaks originate from the TEM grid and the Si(Li)-EDX detector, respectively.

The quantification of these spectra indicates a ratio of Sn to Ge of around 0.25 for the single nolanite-type crystals from #HH228 and 0.18 for the corresponding crystals from #HH266. The height of the O and N signal suggests an approximate 1:1 ratio of O to N, but due to the close proximity of the C, N and O ionization edges a reliable quantification is not possible (Tessier, 2018).

3.3. ADT

The crystals in both samples are too small for single-crystal structure determination by X-ray diffraction, therefore 3D ED was used instead. The advantage of 3D ED is that a crystal structure determination can be performed on a single nanocrystal (Kolb et al., 2007; Gemmi et al., 2019). Thus, even nanocrystalline mixtures of different phases can be investigated. 3D ED has been previously used to solve structures from materials synthesized in large-volume press experiments (Gemmi et al., 2011; Bhat et al., 2015, 2020).

Four ADT datasets were analyzed in this work and labeled Cr1 to Cr4. Cr1 originates from sample #HH228 and Cr2, Cr3 and Cr4 from sample #HH266. Cr1_HH228 and Cr2_HH266 are datasets of the nolanite-type phase, while Cr3_HH266 and Cr4_HH266 are datasets of the 6R polytype. Unit-cell parameters of the crystal structures derived using ADT were refined subsequently from synchrotron PXRD data. Results are provided in Section 3.4.

3.3.1. Sample #HH228

ADT measurements, using a tilt range of −70° to 60°, were performed on SnGe₄N₄O₄ crystals identified via EDX. After data processing a hexagonal unit cell with parameters around a = 5.88 Å, b = 5.84 Å, c = 9.40 Å could be found from ADT measurements.

For this unit cell, systematic extinctions could be found along the c-axis for 000l with only reflections l = 2n being present, corresponding to a 2₁ or 6₃ screw axis [Fig. 3(a)], and for the reflection condition with l = 2n, giving a c-glide plane perpendicular to the 〈210〉 directions [Fig. 3(b)]. As no global extinctions were observed, this results in an extinction symbol of P – – c (trigonal/hexagonal) (Fig. 3). A close inspection of the and reflections shows slight diffuse scattering in the c* direction.

Figure 3 Slices of the reconstructed reciprocal space of the SnGe4N4O4 phase of Cr1_HH228. (a) Viewing direction [110] showing the reflections. For 000l reflections, l = 2n is clearly visible, no other extinctions are visible. (b) Viewing direction showing the reflections, l = 2n is only violated by weak reflections. The grid shown in the figures represents the corresponding projections of the reciprocal unit cell onto the image plane. As a* and b* are not parallel to this plane in the given viewing directions, the grid points representing the projection of a* or b* onto the image plane are not occupied by reflections in the zero layer of the reciprocal space, however in higher layers above and below.

The crystal structure of SnGe₄N₄O₄ could be solved in space groups P31c and P6₃mc from the dataset Cr1_HH228. The higher symmetry space group P6₃mc was chosen because the structure solution and refinement showed no features which would justify the introduction of the additional free parameters of the lower-symmetry space group P31c. Two other hexagonal space groups, namely P6₃/mmc and , are also compatible with the observed extinctions. However, these space groups do not fit to the structure solution, because both contain an additional mirror plane perpendicular to the c-axis. The crystal structure was refined to an R(obs) value of 19.41% using kinematic approximation (completeness 86.6%, resolution 0.5 Å, independent reflections 788). With consideration of dynamical effects, R(obs) decreased to 9.42%. The resulting atomic positions and equivalent isotropic displacement parameters are listed in Table 1 and the crystal structure is shown in Section 3.5.

Table 1
Atomic coordinates, displacement parameters and symmetry information of the nolanite-type SnGe₄N₄O₄ structure (space group P6₃mc) resulting from the dynamical refinement of ADT data of crystal Cr1_HH228

	x	y	z	Uequiv	Wyckoff letter	Site symmetry
Sn1	0.333333	0.666667	0.9666 (3)	0.0070 (4)	2b	3m.
Ge1	0.333333	0.666667	0.5613 (3)	0.0052 (6)	2b	3m.
Ge2	−0.16655 (18)	0.16655 (18)	0.7463 (3)	0.0052 (4)	6c	.m.
N1	0.333333	0.666667	0.3579 (6)	0.007 (2)	2b	3m.
N2	−0.4900 (5)	0.4900 (5)	0.6219 (5)	0.0053 (15)	6c	.m.
O1	0	0	0.6465 (7)	0.0030 (17)	2a	3m.
O2	0.1569 (6)	−0.1569 (6)	0.8573 (4)	0.0105 (18)	6c	.m.

3.3.2. Sample #HH266

In sample #HH266 the same nolanite-type phase as in #HH228 was found, although with slightly shorter a and b axes. ADT data, with tilt range ±60°, delivered unit-cell parameters of a = 5.82 Å, b = 5.84 Å and c = 9.40 Å.

Moreover, the diffraction patterns of most crystals from sample #HH266 display streaks along the c-axis, as well as additional reflections from a second phase [Fig. 4(c)]. This phase has the extinction symbol R – – with a ≃ 5.8 Å (equal to the nolanite-type phase) and a tripled c-axis of around 28.2 Å [Fig. 4(a)], hiding some of the systematic extinctions of the nolanite-type phase [Fig. 4(d)].

Figure 4 Images of the reconstructed reciprocal space. (a) The projection of the reciprocal space of Cr3_HH266 viewed down [010] showing the unit cell of the 6R polytype with the threefold superstructure along c*. (b) The [010] projection of Cr2_HH266 with much less additional reflections along c* compared to (a). The reciprocal unit cell corresponds to the nolanite-type phase. (c) reflections of Cr3_HH266, i.e. a single slice of the reciprocal space, cut out of the projection in (a). In comparison to Cr2_HH266 additional streaks are visible. (d) reflections of Cr2_HH266. The systematic extinctions of the c-glide plane are slightly violated due to additional reflections from the rhombohedral phase. The grid represents the projection of the reciprocal unit cell onto the image plane.

Most of the measured crystals in sample #HH266 exhibit reflections of both the nolanite-type and the 6R polytype with varying relative amounts. Crystal Cr2_HH266 shows very strong intensities of the nolanite-type phase, while for Cr3_HH266 the reflections of the rhombohedral phase are much stronger. Only crystal Cr4_HH266 provided exclusively the reflections of the rhombohedral phase (Fig. 5). It did not show any streaks, which suggests that the observed streaks in the other crystals are due to the two phases exhibiting stacking faults at their phase boundaries.

Figure 5 Reciprocal space of Cr4_HH266. Slice of the reflections, showing the presence of an obverse rhombohedral centering with hkil: −h+k+l = 3n. The l = 2n condition for reflections indicating a c-glide plane is violated giving R – – as an extinction symbol.

Structure solution and refinement of the nolanite-type phase were possible from the dataset Cr2_HH266 (completeness 94.9%, resolution 0.5 Å, independent reflections 465), which shows only weak additional reflections of the rhombohedral phase. The crystal structure could be refined kinematically to an R(obs) value of 21.28% and dynamically to an R(obs) value of 11.25% (Table 2).

Table 2
Atomic coordinates, displacement parameters and symmetry information of the nolanite-type SnGe₄N₄O₄ structure (space group P6₃mc) resulting from the dynamical refinement of ADT data of crystal Cr2_HH266

	x	y	z	Uiso	Occupancy	Wyckoff letter	Site symmetry
Sn1	0.333333	0.666667	0.9648 (6)	0.0032 (6)	0.84 (3)	2b	3m.
Ge(Sn1)	0.333333	0.666667	0.9648 (6)	0.0032 (6)	0.16 (3)	2b	3m.
Ge1	0.333333	0.666667	0.5626 (8)	0.0080 (8)	1	2b	3m.
Ge2	−0.16716 (17)	0.16716 (17)	0.7464 (6)	0.0032 (4)	1	6c	.m.
N1	0.333333	0.666667	0.3558 (17)	0.006 (3)	1	2b	3m.
N2	−0.4899 (5)	0.4899 (5)	0.6231 (11)	0.0038 (11)	1	6c	.m.
O1	0	0	0.6486 (15)	0.0013 (18)	1	2a	3m.
O2	0.1541 (6)	−0.1541 (6)	0.8585 (11)	0.0105 (14)	1	6c	.m.

The crystal structure of the second phase could be determined in space group from datasets Cr4_HH266 (tilt range −40° to 30°, completeness 96.6%, resolution 0.63 Å, independent reflections 502) and Cr3_HH266 (tilt range ±60°, completeness 90.8%, resolution 0.71, independent reflections 342). Structure solution from the dataset Cr3_HH266, was possible despite the presence of additional reflections from the nolanite-type phase. Subsequent refinement of datasets Cr4_HH266 and Cr3_HH266 led to R(obs) values of 24.31% and 30.95%, respectively, taking only the kinematical approximation into account. Taking dynamical scattering into account led to improved R(obs) values of 14.52% and 11.72% (Table 3).

Table 3
Atomic positions, displacement parameters, and symmetry information of the 6R polytype (space group ) resulting from the dynamical refinement of ADT data of crystal Cr4_HH266

	x	y	z	Uiso	Wyckoff letter	Site symmetry
Sn1	0	0	0.42713 (7)	0.0053 (6)	6c	3m
Ge1	0	0	0.06208 (11)	0.0081 (8)	6c	3m
Ge2	0.5	0	0	0.0080 (12)	9e	.2/m
Ge3	0.5	0	0.5	0.0065 (6)	9d	.2/m
O1	0	0	0.7003 (3)	0.0022 (18)	6c	3m
N1	0	0	0.1290 (3)	−0.0035 (17)	6c	3m
N2	0.9834 (13)	0.4917 (7)	0.7084 (2)	0.0055 (12)	18h	.m
O2	0.8447 (8)	0.1553 (8)	0.7962 (2)	0.0188 (16)	18h	.m

3.4. Powder X-ray diffraction

The synchrotron PXRD patterns show reflections of several not yet reported phases, which could be indexed. One of these phases is the novel nolanite-type phase, which could be detected in small quantities in the PXRD patterns of samples #HH228 and #HH266, shown in Figs. S2 and S3. In the PXRD pattern of #HH266, additional reflections consistent with the 6R polytype could be observed (Fig. S3). The unit-cell parameters were refined using a Le Bail fit (Table 4). The PXRD pattern of sample #HH670, which was synthesized at HP-HT conditions similar to #HH266, but from different starting materials, shows a large amount of the novel nolanite-type phase, together with a mixture of rutile-type SnO₂ and GeO₂, and spinel-type Ge₃N₄ (Fig. S4), which are well known phases. Therefore, a Rietveld refinement was possible for this sample. The resulting unit-cell parameters are included in Table 4.

Table 4
Unit-cell parameters of nolanite-type SnGe₄N₄O₄ for different samples and the 6R polytype, derived from the synchrotron PXRD measurements, and from DFT calculations of the nolanite type

	a (Å)	c (Å)	V (Å^3)
#HH228	5.876 (3)	9.418 (5)	281.6 (2)
#HH266	5.839 (1)	9.365 (2)	276.55 (7)
#HH670	5.791 (1)	9.276 (2)	269.38 (7)
6R polytype (#HH266)	5.846 (1)	28.230 (5)	835.5 (2)
DFT	5.818	9.427	276.4

3.5. Structure description of the nolanite-type phase

The structure type found in Cr1_HH228 and Cr2_HH266 was attributed to the mineral nolanite (Hanson, 1958). In the crystal structure (Fig. 6), all atoms are located on mirror planes as indicated by the Wyckoff letters in Tables 1, 2 and 3. The anion sublattice is close-packed with an ABAC stacking sequence of the anions. Sn occupies an octahedral site, while Ge occupies both octahedral and tetrahedral sites. Interatomic distances for the nolanite-type phase can be found in supporting information. The cation-to-anion ratio is 5:8. Both germanium and tin have a valence of 4+, therefore charge neutrality can only be achieved by an N(3−):O(2−) = 1:1 ratio of the anions. As electron diffraction cannot distinguish between the light elements N and O in the presence of heavy metals, the N/O distribution on different sites has been adopted from the results of DFT calculations. The calculation of bond valence sums of the structure refinement further confirms the assignment of O and N (Table S16). All N atoms are fourfold coordinated and all O atoms are threefold coordinated. The N atoms are tetrahedrally coordinated by the cations, similar to the spinel structure, while the O atoms are coordinated in a trigonal pyramid.

Figure 6 Crystal structure of nolanite-type SnGe4N4O4 showing the unit cell and the coordination polyhedra of the cations. O atoms are red, N atoms are blue. Picture generated with Vesta (Momma & Izumi, 2011).

The structure is best described by considering layers perpendicular to the c-axis (Fig. 7). Two different types of layers can be distinguished. The first consists of octahedrally coordinated Ge on a 6c position and is called O-layer, according to the terminology of Grey & Gatehouse (1979). The second is a mixed T₁-layer, containing tetrahedrally coordinated Ge next to octahedrally coordinated Sn on 2b positions. They are shown in Fig. 7(a) in an OT₁O′T₁′ sequence. O-layers are formed by edge-sharing GeN₃O₃ octahedra (Ge2 position), while the T₁-layer is made up of corner-sharing GeN₄ tetrahedra (Ge1 Position) and SnN₃O₃ octahedra, forming rings of alternating Sn- and Ge-centered polyhedra [Fig. 7(b)]. In addition, the SnN₃O₃ octahedra have edges in common with three GeN₃O₃ octahedra of an O-layer (via nitro­gen atoms) and share only corners with the GeN₃O₃ octahedra of the opposite O-layer (via oxygen atoms). The O′T₁′-layers are related to the OT₁-layers by a 180° rotation about the c-axis, provided by the 2₁-screw axis (included in the 6₃-screw axis). The relation of the pairs of layers can also be described by the c-glide plane.

Figure 7 Structure of the nolanite-type phase viewed perpendicular to the c-axis (a) and along the c-axis (b). Ge1 tetrahedra are shown in red and Sn octahedra are shown in turquoise.

3.5.1. Structure description of the rhombohedral phase

The additional rhombohedral phase has the same chemical composition as the nolanite-type SnGe₄N₄O₄. Oxygen and nitro­gen sites were assigned as given in the SnGe₄N₄O₄ nolanite-type structure based on the same criteria, namely, fourfold-coordinated nitro­gen and threefold-coordinated oxygen. The coordination geometry stays identical. Interatomic distances can be found in supporting information. The structure consists of a close-packed anion lattice with cations in octahedral and tetrahedral sites, forming layers (O, T₁) similar to the nolanite-type structure.

T₁-layers containing corner-sharing GeN₄ tetrahedra and SnN₃O₃ octahedra, positioned on the threefold axis, form every second layer [Fig. 8(a)]. In between, there are two slightly different alternating octahedral (O) layers, formed by the symmetrically non-equivalent Ge2 and Ge3 atoms, which are both positioned on inversion centers (site symmetry 2/m). In every second T₁-layer, the tetrahedra are oriented upside down along the c-axis [Figs. 8(a), 8(b)], described by the inversion center. Thus, the OT₁O′T₁′ block is slightly different from that of the nolanite type. Due to the difference of the two O-layers, the 6₃-screw axis and the c-glide plane are lost. The two T₁-layers instead are linked by the inversion center in the O-layers. This building block is tripled by the R-centering. According to the nomenclature for polytypes (Guinier et al., 1984), the structure is a 6R polytype of the nolanite-type SnGe₄N₄O₄.

Figure 8 Structure of the rhombohedral phase, space group . Color code is the same as for the nolanite-type. Now there are two different non-equivalent O-layers formed by octahedra centered by Ge2 (shown in blue) and Ge3 (shown in gray). (a) Projection of the unit cell along [110], visualizing the polyhedron layers. (b) A part of the unit cell in perspective view, highlighting the connections between the different cation polyhedra in more detail.

In the crystal structure of the 6R polytype the stacking sequence can be better understood by considering the stacking of the anion sublattice (Fig. 9). Both crystal structures show a mixture of cubic and hexagonal close packing. The nolanite structure has an ABAC-type stacking, which can be expressed as a c-h-c-h sequence using the notation by Jagodzinski (1949), where c denotes a layer with two different neighbors (cubic) and h one with two identical neighbors (hexagonal). For the 6R polytype, this sequence is 3 × (c-h-h-c). Each c-h-h-c sequence contains two T₁-layers and one O-layer (Ge3), with an O-layer (Ge2) connecting the sequences (Fig. 8). A c-h-h-c sequence shifts by [2/3, 1/3, 1/3] from the one below, creating the rhombohedral centering.

Figure 9 Comparison between the stacking of the anion layers of (a) the rhombohedral phase and (b) the basic nolanite type. The dotted arrows indicate the position of the cations. The O symbol denotes the presence of an O-layer and whether a Ge2 or a Ge3 atom is present. A triangle marks a T1-layer, with the direction of the tip of the triangle indicating the orientation of the GeN4 tetrahedron. Shown are the stacking vectors between the different layers and the resulting hexagonal (hcp) or cubic (ccp) close-packing sequences. In the legend (right-hand side), both the ABC and the Jagodzinski (1949) notation are given.

3.6. Density functional theory: structure elucidation and site preference of anions and cations

Motivated by initial experimental data from 3D ED, nolanite-type structures of SnGe₄N₄O₄ were explored, starting from data available for a magnesium molybdate [Inorganic Crystal Structure Database (ICSD) code: 248080; Abe et al. (2010)] with space group P6₃mc (space group No. 186, Z = 2). Simple valence rules suggest distributing O and N to three- and four-coordinated sites, respectively. The most straightforward pattern to distribute cations is to locate Sn in one of the twofold positions (Wyckoff 2a), resulting in either sixfold or fourfold coordination of tin. The structure with the lowest energy then comprises Sn with octahedral coordination, while Ge occupies the tetrahedral position and the remaining octahedral site (6c). To confirm the result, a series of calculations on alternative models was performed, with all of them leading to structures with higher energy. For example, switching O and N in Wyckoff positions 2a and 2b creates a model still in P6₃mc but with alternating layers of O and N. The energy difference to the lowest energy modification described above is about 1.5 eV per exchanged anion. The high value, which also reflects the costs of exchanging just a single O and N atom, indicates a low probability of finding significant O/N disorder among the anion sites. Similar energy differences are encountered in models with alternative distributions of cations. Placing Sn into the tetrahedral site, while keeping all germanium octahedrally coordinated, yields a model with a penalty of 1.5 eV per exchanged atom. Exchanging Sn and Ge among octahedral sites costs 1.0 eV per atom. Comparing the trends on Sn/Ge exchange supports the strong preference of Sn to occupy octahedral sites in the structure. The results provided feedback and input for further experimental refinement of the crystal structure.

3.7. Atomic resolution STEM

As shown in Fig. 1(b), Ge-rich grains were found, which are expected to be SnGe₄N₄O₄ with nolanite-type structure. Although the crystal structure was solved by ADT (see Section 3.3), the structure is complex. Therefore, it is essential to confirm the validity of the ADT refinement with a direct-space method, i.e. atomic resolution STEM imaging. Fig. 10(a) and Fig. 10(b) show the simultaneously acquired atomic resolution ADF and ABF STEM images, respectively, of the germanium-rich grain prepared by FIB milling. Owing to the Z-contrast nature (Z is the atomic number) in ADF STEM (Pennycook & Boatner, 1988), the cations of Ge and Sn are clearly visualized in Fig. 10(a). On the other hand, ABF STEM imaging has an excellent capability to visualize both heavy and light elements as dark dot contrast, including O and N (Findlay et al., 2010). Combining ADF with ABF STEM imaging, it becomes possible to perform chemical-sensitive imaging of both light elements and heavy elements at an atomic scale. To enhance the signal-to-noise ratio, several tens of unit-cell images are averaged, and the images are given in the inset for the respective images (Ishikawa et al., 2013). The bright atomic columns in Fig. 10(a) correspond to the Sn and Ge atomic columns. The brightness depends not only on the atomic number of the elements but also on the number of atoms in a column because the observation is in projection. For most of the positions, the stacking of atoms along the viewing direction is one atom per unit cell. At these positions, Sn appears brighter than Ge. Only in the octahedral layers, every second Ge atom is stacked with two atoms per unit cell, corresponding to the larger Z-contrast at that position [indicated by numbers 1 and 2 in the inset of Fig. 10(a)].

Figure 10 (a) ADF and (b) ABF atomic resolution STEM images of the nolanite-type phase along the [100] direction. The inset images are generated by unit-cell averaging, and the crystal structure model of Cr2_HH266 is overlaid. The metals are shown as larger balls (Sn gray, Ge light blue) and the anions as smaller balls (O red, N blue). The numbers in the left inset indicate a stacking of one or two germanium atoms per unit cell in the direction of observation.

The structure model of Cr2_HH266 viewed along [100] is overlaid on the inset images, and all the anion and cation atomic columns are excellently matched with the ADT structure model. Therefore, it was directly confirmed that Sn is located not at the tetrahedral 2b, but at the octahedral 2b site.

4. Discussion

The novel phase is isostructural to the mineral nolanite reported by Hanson (1958) with the approximate composition Fe²⁺_2.5V³⁺_1.5V⁴⁺₆O₁₆. The octahedral positions in the O-layers are occupied exclusively by V⁴⁺, whereas the tetrahedra, as well as the octahedra of the T₁-layers, are occupied by a mixture of Fe²⁺ and V³⁺, with an excess of the larger Fe ions in the octahedral position. Gatehouse et al. (1983) described a nolanite mineral with composition (VFeTiAl)₁₀O₁₄(OH)₂. They found only V³⁺ and assigned the tetrahedral position to Fe alone. The remaining Fe excess, together with V, Ti and Al, was assumed to be distributed on the octahedral sites. They were unable to determine the distribution of these elements in the octahedral sites. In the nolanite-type mineral rinmanite (Zn, Mn, Mg)₂(Sb)₂(Fe,Mg)₆O₁₄(OH)₂ (Holtstam et al., 2001), the octahedra of the O-layers are shared by Mg²⁺ and Fe³⁺, whereas Sb⁵⁺ exclusively occupies the octahedra of the T₁-layers (with Sb–O distances of 1.972 Å and 2.022 Å) and the tetrahedra contain a mixture of Zn²⁺ with a little Mn²⁺ and Mg²⁺ (cation–O distances of 1.958 Å and 1.986 Å). The corresponding cation–anion distances in nolanite-type SnGe₄N₄O₄ exhibit a much larger difference between the octahedral and tetrahedral sites of the T₁-layer. The average interatomic distances of 1.89 Å for the tetrahedrally coordinated Ge and 2.11 Å for the octahedral Sn further support the presence of Sn in the octahedral position.

Most of the synthetic nolanite-type compounds found in Pearson's Crystal Data (Villars & Cenzual, 2024) are molybdates with composition A₂Mo₃O₈, where tetravalent Mo occupies the octahedrally coordinated 6c position of the O-layers. The A cation occupies both positions in the T₁-layer, where A may be a single element such as Mg, Mn, Fe, Co, Ni, Zn or Cd (McCarroll et al., 1957), or a mixture of two elements as in (Sc,Zn)₂Mo₃O₈ (Torardi & McCarley, 1985), (Li,Sc)₂Mo₃O₈ (Kerner-Czeskleba & Tourne, 1976) and (InLi)₂Mo₃O₈ (Kerner-Czeskleba & Tourne, 1976). In these compounds, the site preference in the T₁-layer has not been investigated, or the close similarity of the corresponding ionic radii does not indicate a site preference. Rinmanite and nolanite are the only known isostructural compounds where the two positions in the T₁-layer are occupied by different atoms.

Other examples, related to the nolanite-type structures, are the minerals from the nigerite group, which are polysomatic intergrowths of nolanite and spinel modules (Armbruster, 2002; Hejny & Armbruster, 2002; Grey & Gatehouse, 1979). In these minerals, Sn⁴⁺ occupies exclusively the octahedral positions of the T₁-layer of the nolanite modules, showing the same preference as Sn⁴⁺ in the nolanite-type SnGe₄N₄O₄. No nitro­gen-containing nolanite-type structures are reported in the Pearson database or the ICSD.

4.1. Description of the anion sublattice

To better understand both polytypes, considering the stacking of the anion sublattice can be helpful. The nolanite structure type and the 6R polytype differ in the stacking sequence of the anion layer. In both structures, the anion layers along c contain either three nitro­gen and one oxygen or three oxygen and one nitro­gen. In the nolanite type, a nitro­gen-rich layer is always followed by an oxygen-rich layer, while in the 6R polytype, two nitro­gen-rich layers are followed by two oxygen-rich layers (Fig. 9). This leads to the presence of two different O-layers, where one consists of GeN₄O₂ octahedra which are connected to the T₁-layers via edge sharing and the other of GeN₂O₄ octahedra connected to the T₁-layers via corner sharing. A nitro­gen-rich layer connects the O-layer and the octahedra of the T₁-layer via edge sharing while an oxygen-rich layer does this via corner sharing.

This follows the observation from Grey & Gatehouse (1979) for the högbomite mineral series that for a c-c sequence (Jagodzinski notation) the O-layer is connected to the T₁-layers via edge-sharing, while for an h-h sequence, it is via corner-sharing. In Fig. 9 it can be seen that for both the 6R polytype and the nolanite type, the oxygen-rich layers have the Jagodzinski symbol h (are hexagonal close-packed), while the nitro­gen-rich layers have the symbol c (are cubic close-packed).

One example is the mineral group högbomite built up from an anion sublattice with both hexagonal and cubic close packed stacking sequences, which is characterized by polysomatic intergrowths of modules of nolanite and spinel (Armbruster, 2002). The nolanite modules allow the incorporation of cations with different ionic radii and different valence into the structure. In the cubic close-packed modules of the 6R polytype, no additional tetrahedral gap is occupied and, therefore, no spinel-like T₂-layer is present. Thus, the nominal ratio of tin to germanium remains the same (1:4) as in the nolanite-type structure. Accordingly, it seems that the appearance of the 6R polytype is due to the ordering of the anion layers and not due to the presence of additional cations. This is different compared to the högbomite minerals where the cubic close-packed and the hexagonal close-packed O-layers contain different cations. This shows that for oxynitride compounds based on close-packing, different stacking sequences of the anion layers are possible, allowing the formation of polytypes.

4.2. Comparison of results from different samples #HH228, #HH266 and #HH670

The two samples #HH228 (∼20 GPa, ∼1500°C, preparation under air) and #HH266 (∼16 GPa, ∼1200°C, preparation in a glovebox) have been synthesized at considerably different pressures and temperatures from an amorphous single-source precursor. This precursor consists of a homogeneous mixture of Sn, Ge, O and N at the atomic scale. The nolanite-type phase has been identified in the oxygen-exposed sample #HH228 and in the sample #HH266 which was protected from oxygen. From a qualitative comparison of the PXRD patterns of both samples it can be seen that #HH266 contains a higher amount of the nolanite-type phase (Figs. S2 and S3). The samples exhibit strong differences in the remaining phases present. α-PbO₂-type SnO₂ was not detected in #HH266, only in #HH228, most likely due to additional oxygen present in the sample. The investigation of the nolanite-type phase from both samples showed some small, but notable differences. The nolanite-type phase synthesized at higher pressure and temperature (#HH228) has a unit-cell volume of V = 281.6 ų, compared to V = 276.5 ų for the nolanite-type phase from #HH266. The chemical composition derived from EDX is Sn: Ge = 1:4 in #HH228, which corresponds to the ideal stoichiometric composition SnGe₄N₄O₄. For the crystals from #HH266, the EDX measurements on average show a smaller ratio of Sn:Ge = 0.75:4, which correlates with the smaller unit-cell volume. This can be explained by a partial replacement of Sn by Ge. An occupancy refinement of the cation positions of the nolanite structure from the dataset Cr2_HH266 confirmed this result with additional Ge replacing some Sn on the octahedral position leading to a ratio of Sn: Ge of around 0.8:4 (Table 2). Furthermore, in the PXRD of sample #HH266 the 6R polytype was detected (Fig. S3), which is not present in the PXRD of #HH228.

To verify the results from samples #HH228 and #HH266 another synthesis was made, using a different precursor material. Sample #HH670 was prepared from a mechanical mixture of crystalline phases, namely, rutile-type SnO₂ and sinoite-type Ge₂N₂O matching the chemical composition of SnGeN₄O₄. For comparison, the sample was synthesized at the same P/T conditions as #HH266. The resulting different phase composition is attributed to the different starting materials. The crystalline precursor powder is a less homogenous starting material in comparison to that of the polymeric single source precursor derived material. Therefore, while #HH670 contains a large amount of the novel nolanite-type phase, it contains significant amounts of unreacted rutile-type SnO₂ and left-over Ge in the form of rutile-type GeO₂ and spinel-type Ge₃N₄. The unit-cell volume V = 269.4 ų of the nolanite-type phase in sample #HH670 is even smaller in comparison to the other samples, suggesting an even larger Sn deficit. This was confirmed by the Rietveld refinement of sample #HH670, which resulted in a Sn occupancy of about 0.8, corresponding to a Sn:Ge ratio of 0.8:4. A partial replacement of Sn by Ge could not be quantified from the PXRD data. Qualitatively, the varying Sn occupancy in the different samples is clearly visible in the PXRD patterns by the variation of the relative intensity of some low-angle reflections, as compared to simulated powder patterns (Fig. 11). The fact that the new phase has been synthesized using two different routes suggests that the nolanite-type phase is indeed thermodynamically stable, at least under high-pressure conditions.

Figure 11 Comparison of the three low-angle reflections (marked by black arrows) of SnGe4N4O4 from different samples. These reflections are only marginally affected by overlap with other phases (indicated by orange arrows). Left-hand column: synchrotron powder XRD patterns (λ = 0.207 Å) as measured. Right-hand column: powder patterns simulated from the structure model (atomic positions from DFT results). Only for sample #HH228 the relative intensity of these three reflections corresponds to the simulation which assumes the octahedral site is fully occupied by Sn. For the other samples, #HH266 and #HH670, the relative intensity qualitatively corresponds to a simulation with a certain Sn deficit. This supports the idea that the lower unit-cell volume of crystals from #HH266 and #HH670, as compared to #HH228, is caused by a slightly lower Sn content.

5. Conclusion

In this study a new nolanite-type mixed Sn Ge oxynitride was synthesized under high-pressure high-temperature conditions. The crystal structure was solved via ADT, a 3D ED method and characterized with a combination of PXRD, EDX, 3D ED, DFT calculation and atomic resolution STEM. This phase is the first nolanite-type oxynitride, as well as the first mixed Sn Ge oxynitride phase reported in the literature. The crystal structure is made up of a close-packed anion lattice with Ge being present in both tetrahedral and octahedral coordination and Sn in octahedral coordination. DFT calculations suggested that the O and N atoms are not randomly distributed on the anion positions, but instead occupy distinct positions. Using a variety of different methods, it could be established that the Sn occupies the octahedral position in the T₁-layer, while the Ge occurs in both tetrahedral and octahedral coordination. This is similar to Ge₃N₄, which under high-pressure conditions forms the spinel structure where the Ge shows both tetrahedral and octahedral coordination (Leinenweber et al., 1999). The octahedral coordination of Sn is in agreement with high-pressure studies of SnO₂ (Haines & Léger, 1997; Ono et al., 2005).

Differences in the unit-cell parameters from PXRD between the different samples and the different results from EDX measurements suggest that up to 20% of the Sn can be replaced by germanium.

In addition to the nolanite-type structure, in sample #HH266 a 6R polytype of the nolanite-type phase with a more complex stacking order could be identified and its crystal structure was solved and refined.

In conclusion, it is possible to produce mixed SnGe oxynitride compounds via high-pressure high-temperature synthesis. This opens pathways for new compounds with interesting properties and might shed further light on the behavior of Sn and Ge compounds under high-pressure conditions.

6. Related literature

The following references, not cited in the main body of the paper, have been cited in the supporting information: Brese & O'Keeffe (1991); Brown (2020); Gagné & Hawthorne (2015).

Supporting information

Computing details

(Cr1_HH228)

Crystal data

Ge4N4O4Sn	Z = 2
Mr = 529.1	F(000) = 114.294
Hexagonal, P63mc	Dx = 6.240 Mg m^−3
Hall symbol: P 6c -2c	Electron radiation, λ = 0.0197 Å
a = 5.876 (3) Å	µ = 0 mm^−1
c = 9.418 (5) Å	T = 293 K
V = 281.6 (2) Å^3

Data collection

Tecnai F30 ST diffractometer	θmax = 1.1°, θmin = 0.1°
ADT with precession scans	h = −9→10
18262 measured reflections	k = −9→9
2989 independent reflections	l = −16→16
2576 reflections with I > 3σ(I)

Refinement

Refinement on F	1 constraint
R[F^2 > 2σ(F^2)] = 0.094	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + (0.01P)^2] where P = (Fo + 2Fc)/3
wR(F^2) = 0.106	(Δ/σ)max = 0.031
S = 3.37	Δρmax = 0.56 e Å^−3
2989 reflections	Δρmin = −0.40 e Å^−3
162 parameters	Absolute structure: 346 of Friedel pairs used in the refinement
0 restraints

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

	x	y	z	Uiso*/Ueq
Sn1	0.333333	0.666667	−0.0334 (3)	0.0070 (4)
Ge1	0.333333	0.666667	−0.4387 (3)	0.0052 (6)
Ge2	−0.16655 (18)	0.16655 (18)	−0.2537 (3)	0.0052 (4)
N1	0.333333	0.666667	0.3579 (6)	0.007 (2)
N2	−0.4900 (5)	0.4900 (5)	−0.3781 (5)	0.0053 (15)
O1	0	0	−0.3535 (7)	0.0030 (17)
O2	0.1569 (6)	−0.1569 (6)	−0.1427 (4)	0.0105 (18)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.0074 (5)	0.0074 (5)	0.0062 (6)	0.0037 (3)	0	0
Ge1	0.0057 (7)	0.0057 (7)	0.0044 (8)	0.0028 (4)	0	0
Ge2	0.0051 (4)	0.0051 (4)	0.0066 (5)	0.0034 (5)	0.0002 (2)	−0.0002 (2)
N1	0.009 (3)	0.009 (3)	0.002 (4)	0.0046 (15)	0	0
N2	0.0062 (16)	0.0062 (16)	0.0024 (18)	0.002 (2)	−0.0029 (9)	0.0029 (9)
O1	0.002 (2)	0.002 (2)	0.004 (3)	0.0011 (10)	0	0
O2	0.011 (2)	0.011 (2)	0.013 (2)	0.009 (2)	0.0021 (8)	−0.0021 (8)

Geometric parameters (Å, º)

Sn1—N2^i	2.164 (4)	Ge1—N2^ix	1.886 (4)
Sn1—N2^ii	2.164 (4)	Ge1—N2^x	1.886 (4)
Sn1—N2^iii	2.164 (4)	Ge2—N1^xi	1.997 (4)
Sn1—O2^iv	2.070 (4)	Ge2—N2^xii	2.023 (4)
Sn1—O2^v	2.070 (4)	Ge2—N2^x	2.023 (4)
Sn1—O2^vi	2.070 (4)	Ge2—O1	1.938 (3)
Ge1—N1^vii	1.915 (7)	Ge2—O2^v	1.952 (4)
Ge1—N2^viii	1.886 (4)	Ge2—O2^xiii	1.952 (4)
N2^i—Sn1—N2^ii	79.34 (17)	N2^xii—Ge2—O1	96.22 (19)
N2^i—Sn1—N2^iii	79.34 (17)	N2^xii—Ge2—O2^v	177.0 (2)
N2^i—Sn1—O2^iv	167.30 (19)	N2^xii—Ge2—O2^xiii	91.79 (17)
N2^i—Sn1—O2^v	90.93 (15)	N2^x—Ge2—O1	96.22 (19)
N2^i—Sn1—O2^vi	90.93 (15)	N2^x—Ge2—O2^v	91.79 (17)
N2^ii—Sn1—N2^iii	79.34 (14)	N2^x—Ge2—O2^xiii	177.0 (2)
N2^ii—Sn1—O2^iv	90.93 (16)	O1—Ge2—O2^v	81.84 (18)
N2^ii—Sn1—O2^v	167.30 (19)	O1—Ge2—O2^xiii	81.84 (18)
N2^ii—Sn1—O2^vi	90.93 (13)	O2^v—Ge2—O2^xiii	90.20 (19)
N2^iii—Sn1—O2^iv	90.93 (16)	Ge1^xiv—N1—Ge2^i	121.77 (16)
N2^iii—Sn1—O2^v	90.93 (13)	Ge1^xiv—N1—Ge2^ii	121.77 (16)
N2^iii—Sn1—O2^vi	167.30 (19)	Ge1^xiv—N1—Ge2^iii	121.77 (16)
O2^iv—Sn1—O2^v	97.42 (17)	Ge2^i—N1—Ge2^ii	94.8 (2)
O2^iv—Sn1—O2^vi	97.42 (17)	Ge2^i—N1—Ge2^iii	94.8 (2)
O2^v—Sn1—O2^vi	97.42 (15)	Ge2^ii—N1—Ge2^iii	94.8 (2)
N1^vii—Ge1—N2^viii	107.61 (16)	Sn1^xi—N2—Ge1^xv	119.9 (2)
N1^vii—Ge1—N2^ix	107.61 (16)	Sn1^xi—N2—Ge2^xii	96.87 (15)
N1^vii—Ge1—N2^x	107.61 (16)	Sn1^xi—N2—Ge2^x	96.87 (15)
N2^viii—Ge1—N2^ix	111.27 (17)	Ge1^xv—N2—Ge2^xii	121.79 (17)
N2^viii—Ge1—N2^x	111.27 (17)	Ge1^xv—N2—Ge2^x	121.79 (17)
N2^ix—Ge1—N2^x	111.27 (17)	Ge2^xii—N2—Ge2^x	93.24 (19)
N1^xi—Ge2—N2^xii	85.79 (18)	Ge2—O1—Ge2^v	98.5 (2)
N1^xi—Ge2—N2^x	85.79 (18)	Ge2—O1—Ge2^xiii	98.5 (2)
N1^xi—Ge2—O1	177.2 (2)	Ge2^v—O1—Ge2^xiii	98.5 (2)
N1^xi—Ge2—O2^v	96.23 (19)	Sn1^xvi—O2—Ge2^v	126.82 (16)
N1^xi—Ge2—O2^xiii	96.23 (19)	Sn1^xvi—O2—Ge2^xiii	126.82 (16)
N2^xii—Ge2—N2^x	86.14 (18)	Ge2^v—O2—Ge2^xiii	97.54 (19)

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

(Cr2_HH266)

Crystal data

Ge4.158N4O4Sn0.842	Z = 2
Mr = 521.8	F(000) = 113.24
Hexagonal, P63mc	Dx = 6.267 Mg m^−3
Hall symbol: P 6c -2c	Electron radiation, λ = 0.0197 Å
a = 5.839 (1) Å	µ = 0 mm^−1
c = 9.365 (2) Å	T = 293 K
V = 276.55 (7) Å^3

Data collection

Tecnai F30 ST diffractometer	θmax = 1.3°, θmin = 0.1°
ADT with precession scans	h = −12→12
41049 measured reflections	k = −12→12
2369 independent reflections	l = −20→20
2275 reflections with I > 3σ(I)

Refinement

Refinement on F	3 constraints
R[F^2 > 2σ(F^2)] = 0.113	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.134	(Δ/σ)max = 0.028
S = 4.83	Δρmax = 0.80 e Å^−3
2369 reflections	Δρmin = −0.32 e Å^−3
140 parameters	Absolute structure: 278 of Friedel pairs used in the refinement
0 restraints

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Sn1	0.333333	0.666667	−0.0352 (6)	0.0032 (6)*	0.84 (3)
Gesn1	0.333333	0.666667	−0.0352 (6)	0.0032 (6)*	0.16 (3)
Ge1	0.333333	0.666667	−0.4374 (8)	0.0080 (8)*
Ge2	−0.16716 (17)	0.16716 (17)	−0.2536 (6)	0.0032 (4)*
N1	0.333333	0.666667	0.3558 (17)	0.006 (3)*
N2	−0.4899 (5)	0.4899 (5)	−0.3769 (11)	0.0038 (11)*
O1	0	0	−0.3514 (15)	0.0013 (18)*
O2	0.1541 (6)	−0.1541 (6)	−0.1415 (11)	0.0105 (14)*

Geometric parameters (Å, º)

Sn1—Gesn1	0	Gesn1—O2^vi	2.069 (7)
Sn1—N2^i	2.169 (8)	Ge1—N1^vii	1.936 (18)
Sn1—N2^ii	2.169 (8)	Ge1—N2^viii	1.875 (5)
Sn1—N2^iii	2.169 (8)	Ge1—N2^ix	1.875 (5)
Sn1—O2^iv	2.069 (7)	Ge1—N2^x	1.875 (5)
Sn1—O2^v	2.069 (7)	Ge2—N1^xi	1.969 (9)
Sn1—O2^vi	2.069 (7)	Ge2—N2^xii	2.001 (7)
Gesn1—N2^i	2.169 (8)	Ge2—N2^x	2.001 (7)
Gesn1—N2^ii	2.169 (8)	Ge2—O1	1.923 (7)
Gesn1—N2^iii	2.169 (8)	Ge2—O2^v	1.937 (7)
Gesn1—O2^iv	2.069 (7)	Ge2—O2^xiii	1.937 (7)
Gesn1—O2^v	2.069 (7)
Gesn1—Sn1—N2^i	0	N1^vii—Ge1—N2^x	107.6 (4)
Gesn1—Sn1—N2^ii	0	N2^viii—Ge1—N2^ix	111.3 (3)
Gesn1—Sn1—N2^iii	0	N2^viii—Ge1—N2^x	111.3 (3)
Gesn1—Sn1—O2^iv	0	N2^ix—Ge1—N2^x	111.3 (3)
Gesn1—Sn1—O2^v	0	N1^xi—Ge2—N2^xii	85.5 (4)
Gesn1—Sn1—O2^vi	0	N1^xi—Ge2—N2^x	85.5 (4)
N2^i—Sn1—N2^ii	78.4 (3)	N1^xi—Ge2—O1	177.1 (6)
N2^i—Sn1—N2^iii	78.4 (3)	N1^xi—Ge2—O2^v	96.9 (4)
N2^i—Sn1—O2^iv	165.7 (4)	N1^xi—Ge2—O2^xiii	96.9 (4)
N2^i—Sn1—O2^v	90.5 (3)	N2^xii—Ge2—N2^x	86.5 (3)
N2^i—Sn1—O2^vi	90.5 (3)	N2^xii—Ge2—O1	96.6 (4)
N2^ii—Sn1—N2^iii	78.4 (3)	N2^xii—Ge2—O2^v	177.4 (4)
N2^ii—Sn1—O2^iv	90.5 (3)	N2^xii—Ge2—O2^xiii	92.5 (3)
N2^ii—Sn1—O2^v	165.7 (4)	N2^x—Ge2—O1	96.6 (4)
N2^ii—Sn1—O2^vi	90.5 (2)	N2^x—Ge2—O2^v	92.5 (3)
N2^iii—Sn1—O2^iv	90.5 (3)	N2^x—Ge2—O2^xiii	177.4 (4)
N2^iii—Sn1—O2^v	90.5 (2)	O1—Ge2—O2^v	81.0 (3)
N2^iii—Sn1—O2^vi	165.7 (4)	O1—Ge2—O2^xiii	81.0 (3)
O2^iv—Sn1—O2^v	98.8 (3)	O2^v—Ge2—O2^xiii	88.3 (3)
O2^iv—Sn1—O2^vi	98.8 (3)	Ge1^xiv—N1—Ge2^i	121.4 (4)
O2^v—Sn1—O2^vi	98.8 (3)	Ge1^xiv—N1—Ge2^ii	121.4 (4)
Sn1—Gesn1—N2^i	0	Ge1^xiv—N1—Ge2^iii	121.4 (4)
Sn1—Gesn1—N2^ii	0	Ge2^i—N1—Ge2^ii	95.4 (6)
Sn1—Gesn1—N2^iii	0	Ge2^i—N1—Ge2^iii	95.4 (6)
Sn1—Gesn1—O2^iv	0	Ge2^ii—N1—Ge2^iii	95.4 (6)
Sn1—Gesn1—O2^v	0	Sn1^xi—N2—Gesn1^xi	0
Sn1—Gesn1—O2^vi	0	Sn1^xi—N2—Ge1^xv	119.3 (5)
N2^i—Gesn1—N2^ii	78.4 (3)	Sn1^xi—N2—Ge2^xii	97.1 (2)
N2^i—Gesn1—N2^iii	78.4 (3)	Sn1^xi—N2—Ge2^x	97.1 (2)
N2^i—Gesn1—O2^iv	165.7 (4)	Gesn1^xi—N2—Ge1^xv	119.3 (5)
N2^i—Gesn1—O2^v	90.5 (3)	Gesn1^xi—N2—Ge2^xii	97.1 (2)
N2^i—Gesn1—O2^vi	90.5 (3)	Gesn1^xi—N2—Ge2^x	97.1 (2)
N2^ii—Gesn1—N2^iii	78.4 (3)	Ge1^xv—N2—Ge2^xii	121.9 (2)
N2^ii—Gesn1—O2^iv	90.5 (3)	Ge1^xv—N2—Ge2^x	121.9 (2)
N2^ii—Gesn1—O2^v	165.7 (4)	Ge2^xii—N2—Ge2^x	93.3 (4)
N2^ii—Gesn1—O2^vi	90.5 (2)	Ge2—O1—Ge2^v	99.2 (5)
N2^iii—Gesn1—O2^iv	90.5 (3)	Ge2—O1—Ge2^xiii	99.2 (5)
N2^iii—Gesn1—O2^v	90.5 (2)	Ge2^v—O1—Ge2^xiii	99.2 (5)
N2^iii—Gesn1—O2^vi	165.7 (4)	Sn1^xvi—O2—Gesn1^xvi	0
O2^iv—Gesn1—O2^v	98.8 (3)	Sn1^xvi—O2—Ge2^v	125.68 (18)
O2^iv—Gesn1—O2^vi	98.8 (3)	Sn1^xvi—O2—Ge2^xiii	125.68 (18)
O2^v—Gesn1—O2^vi	98.8 (3)	Gesn1^xvi—O2—Ge2^v	125.68 (18)
N1^vii—Ge1—N2^viii	107.6 (4)	Gesn1^xvi—O2—Ge2^xiii	125.68 (18)
N1^vii—Ge1—N2^ix	107.6 (4)	Ge2^v—O2—Ge2^xiii	98.2 (4)

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

(Cr3_HH266)

Crystal data

Ge24N24O24Sn6	F(000) = 342.882
Mr = 3174.6	Dx = 6.309 Mg m^−3
Trigonal, R3m	Electron radiation, λ = 0.0197 Å
Hall symbol: -R 3 2"	Cell parameters from none reflections
a = 5.846 (1) Å	θ = none–none°
c = 28.23 (5) Å	µ = 0 mm^−1
V = 835.52 Å^3	T = none K
Z = 1

Data collection

Tecnai F30 ST diffractometer	θmax = 0.8°, θmin = 0.1°
ADT with precession scans	h = −7→6
9657 measured reflections	k = −8→8
1734 independent reflections	l = −39→34
1577 reflections with I > 3σ(I)

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.117	0 constraints
wR(F^2) = 0.139	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + (0.01P)^2] where P = (Fo + 2Fc)/3
S = 5.01	(Δ/σ)max = 0.046
1734 reflections	Δρmax = 0.51 e Å^−3
148 parameters	Δρmin = −0.56 e Å^−3

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

	x	y	z	Uiso*/Ueq
Sn1	−0.333333	0.333333	0.76041 (9)	−0.0006 (7)*
Ge1	0.333333	0.666667	0.72862 (13)	0.0034 (9)*
Ge2	−0.166667	0.666667	0.666667	−0.0013 (7)*
Ge3	0.166667	0.333333	0.833333	−0.0036 (7)*
N2	−0.0207 (14)	0.4897 (7)	0.7092 (2)	−0.0002 (15)*
O2	−0.1573 (7)	0.1573 (7)	0.7956 (2)	0.0059 (15)*
O1	0	1	0.7003 (3)	−0.002 (2)*
N1	0.333333	0.666667	0.7963 (3)	−0.0189 (16)*

Geometric parameters (Å, º)

Sn1—N2	2.144 (7)	Ge2—N2^i	2.031 (5)
Sn1—N2^i	2.144 (8)	Ge2—N2^v	2.031 (7)
Sn1—N2^ii	2.144 (7)	Ge2—N2^vi	2.031 (9)
Sn1—O2	2.042 (6)	Ge2—O1	1.936 (5)
Sn1—O2^i	2.042 (6)	Ge2—O1^vii	1.936 (5)
Sn1—O2^ii	2.042 (6)	Ge3—O2	1.957 (5)
Ge1—N2	1.874 (7)	Ge3—O2^viii	1.957 (6)
Ge1—N2^iii	1.874 (8)	Ge3—O2^ix	1.957 (5)
Ge1—N2^iv	1.874 (7)	Ge3—O2^x	1.957 (6)
Ge1—N1	1.911 (9)	Ge3—N1	1.985 (4)
Ge2—N2	2.031 (7)	Ge3—N1^xi	1.985 (4)
N2—Sn1—N2^i	79.5 (2)	O1—Ge2—O1^vii	180
N2—Sn1—N2^ii	79.5 (2)	O2—Ge3—O2^viii	89.6 (2)
N2—Sn1—O2	90.3 (2)	O2—Ge3—O2^ix	180
N2—Sn1—O2^i	90.35 (18)	O2—Ge3—O2^x	90.4 (2)
N2—Sn1—O2^ii	166.8 (3)	O2—Ge3—N1	95.8 (2)
N2^i—Sn1—N2^ii	79.5 (3)	O2—Ge3—N1^xi	84.2 (2)
N2^i—Sn1—O2	166.8 (3)	O2^viii—Ge3—O2^ix	90.4 (2)
N2^i—Sn1—O2^i	90.3 (3)	O2^viii—Ge3—O2^x	180
N2^i—Sn1—O2^ii	90.3 (2)	O2^viii—Ge3—N1	95.80 (19)
N2^ii—Sn1—O2	90.3 (3)	O2^viii—Ge3—N1^xi	84.21 (19)
N2^ii—Sn1—O2^i	166.8 (3)	O2^ix—Ge3—O2^x	89.6 (2)
N2^ii—Sn1—O2^ii	90.3 (2)	O2^ix—Ge3—N1	84.2 (2)
O2—Sn1—O2^i	98.3 (2)	O2^ix—Ge3—N1^xi	95.8 (2)
O2—Sn1—O2^ii	98.3 (2)	O2^x—Ge3—N1	84.21 (19)
O2^i—Sn1—O2^ii	98.3 (2)	O2^x—Ge3—N1^xi	95.79 (19)
N2—Ge1—N2^iii	111.8 (3)	N1—Ge3—N1^xi	180
N2—Ge1—N2^iv	111.8 (3)	Sn1—N2—Ge1	120.6 (3)
N2—Ge1—N1	107.0 (2)	Sn1—N2—Ge2	97.5 (3)
N2^iii—Ge1—N2^iv	111.8 (4)	Sn1—N2—Ge2^ii	97.47 (18)
N2^iii—Ge1—N1	107.0 (2)	Ge1—N2—Ge2	121.4 (2)
N2^iv—Ge1—N1	107.0 (2)	Ge1—N2—Ge2^ii	121.4 (4)
N2—Ge2—N2^i	84.9 (3)	Ge2—N2—Ge2^ii	92.0 (3)
N2—Ge2—N2^v	95.1 (3)	Sn1—O2—Ge3	126.80 (19)
N2—Ge2—N2^vi	180	Sn1—O2—Ge3^xii	126.80 (19)
N2—Ge2—O1	95.5 (2)	Ge3—O2—Ge3^xii	96.7 (3)
N2—Ge2—O1^vii	84.5 (2)	Ge2—O1—Ge2^xiii	98.1 (3)
N2^i—Ge2—N2^v	180	Ge2—O1—Ge2^xiv	98.1 (3)
N2^i—Ge2—N2^vi	95.1 (3)	Ge2^xiii—O1—Ge2^xiv	98.1 (3)
N2^i—Ge2—O1	95.5 (3)	Ge1—N1—Ge3	121.78 (19)
N2^i—Ge2—O1^vii	84.5 (3)	Ge1—N1—Ge3^iii	121.78 (19)
N2^v—Ge2—N2^vi	84.9 (3)	Ge1—N1—Ge3^iv	121.78 (19)
N2^v—Ge2—O1	84.5 (2)	Ge3—N1—Ge3^iii	94.8 (3)
N2^v—Ge2—O1^vii	95.5 (2)	Ge3—N1—Ge3^iv	94.8 (3)
N2^vi—Ge2—O1	84.5 (3)	Ge3^iii—N1—Ge3^iv	94.8 (3)
N2^vi—Ge2—O1^vii	95.5 (3)

Symmetry codes: (i) −y, x−y+1, z; (ii) −x+y−1, −x, z; (iii) −y+1, x−y+1, z; (iv) −x+y, −x+1, z; (v) x−y+2/3, −y+4/3, −z+4/3; (vi) −x−1/3, −x+y+1/3, −z+4/3; (vii) y−4/3, x+1/3, −z+4/3; (viii) −x+y, −x, z; (ix) y+1/3, x+2/3, −z+5/3; (x) x−y+1/3, −y+2/3, −z+5/3; (xi) y−2/3, x−1/3, −z+5/3; (xii) −y, x−y, z; (xiii) −y+1, x−y+2, z; (xiv) −x+y−1, −x+1, z.

(Cr4_HH266)

Crystal data

Ge4N4O4Sn	F(000) = 342.882
Mr = 3174.6	Dx = 6.309 Mg m^−3
Trigonal, R3m	Electron radiation, λ = 0.0197 Å
Hall symbol: -R 3 2"	Cell parameters from none reflections
a = 5.846 (1) Å	θ = none–none°
c = 28.230 (5) Å	µ = 0 mm^−1
V = 835.52 Å^3	T = none K
Z = 1

Data collection

Tecnai F30 ST diffractometer	θmax = 1.2°, θmin = 0.1°
ADT with precession scans	h = −11→11
32673 measured reflections	k = −10→10
2279 independent reflections	l = −56→56
1504 reflections with I > 3σ(I)

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.145	0 constraints
wR(F^2) = 0.162	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + (0.01P)^2] where P = (Fo + 2Fc)/3
S = 3.65	(Δ/σ)max = 0.047
2279 reflections	Δρmax = 1.08 e Å^−3
88 parameters	Δρmin = −1.12 e Å^−3

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

	x	y	z	Uiso*/Ueq
Sn1	−0.333333	0.333333	0.76046 (7)	0.0053 (6)*
Ge1	0.333333	0.666667	0.72874 (11)	0.0081 (8)*
Ge2	−0.166667	0.666667	0.666667	0.0080 (6)*
Ge3	0.166667	0.333333	0.833333	0.0065 (6)*
N2	−0.0166 (13)	0.4917 (7)	0.7084 (2)	0.0055 (12)*
O2	−0.1553 (8)	0.1553 (8)	0.7962 (2)	0.0188 (16)*
O1	0	1	0.7004 (3)	0.0022 (18)*
N1	0.333333	0.666667	0.7957 (3)	−0.0035 (17)*

Geometric parameters (Å, º)

Sn1—N2	2.175 (6)	Ge3—Ge3^xi	2.923
Sn1—N2^i	2.175 (7)	Ge3—Ge3^iv	2.923
Sn1—N2^ii	2.175 (6)	Ge3—O2	1.940 (5)
Sn1—O2	2.067 (6)	Ge3—O2^xi	1.940 (6)
Sn1—O2^i	2.067 (6)	Ge3—O2^xii	1.940 (5)
Sn1—O2^ii	2.067 (6)	Ge3—O2^xiii	1.940 (6)
Ge1—N2	1.862 (7)	Ge3—N1	1.995 (4)
Ge1—N2^iii	1.862 (8)	Ge3—N1^xiv	1.995 (4)
Ge1—N2^iv	1.862 (7)	N2—N2^i	2.778 (10)
Ge1—N1	1.889 (8)	N2—N2^ii	2.778 (7)
Ge2—Ge2^i	2.923	N2—N2^xv	2.948 (9)
Ge2—Ge2^v	2.923	N2—N2^vii	2.948 (7)
Ge2—Ge2^ii	2.923	N2—O1^xvi	2.933 (6)
Ge2—Ge2^vi	2.923	N2—O1	2.933 (5)
Ge2—N2	2.025 (7)	N2—O1^ix	2.666 (9)
Ge2—N2^i	2.025 (4)	O2—O2^x	2.723 (8)
Ge2—N2^vii	2.025 (7)	O2—O2^xi	2.723 (8)
Ge2—N2^viii	2.025 (9)	O2—O2^xiii	2.763 (8)
Ge2—O1	1.937 (4)	O2—O2^xvii	2.763 (8)
Ge2—O1^ix	1.937 (4)	O2—N1^xviii	2.925 (3)
Ge3—Ge3^x	2.923	O2—N1	2.925 (3)
Ge3—Ge3^iii	2.923	O2—N1^xiv	2.632 (9)
N2—Sn1—N2^i	79.4 (2)	Ge3—O2—O2^xiii	44.58 (18)
N2—Sn1—N2^ii	79.4 (2)	Ge3—O2—O2^xvii	98.0 (3)
N2—Sn1—O2	90.5 (2)	Ge3—O2—N1^xviii	140.4 (3)
N2—Sn1—O2^i	90.50 (18)	Ge3—O2—N1	42.70 (14)
N2—Sn1—O2^ii	166.8 (2)	Ge3—O2—N1^xiv	48.91 (13)
N2^i—Sn1—N2^ii	79.4 (3)	Ge3^x—O2—O2^x	45.42 (15)
N2^i—Sn1—O2	166.8 (3)	Ge3^x—O2—O2^xi	92.9 (2)
N2^i—Sn1—O2^i	90.5 (3)	Ge3^x—O2—O2^xiii	98.0 (3)
N2^i—Sn1—O2^ii	90.5 (2)	Ge3^x—O2—O2^xvii	44.58 (18)
N2^ii—Sn1—O2	90.5 (3)	Ge3^x—O2—N1^xviii	42.70 (14)
N2^ii—Sn1—O2^i	166.8 (2)	Ge3^x—O2—N1	140.4 (3)
N2^ii—Sn1—O2^ii	90.5 (2)	Ge3^x—O2—N1^xiv	48.91 (13)
O2—Sn1—O2^i	98.1 (2)	O2^x—O2—O2^xi	60.00 (16)
O2—Sn1—O2^ii	98.1 (2)	O2^x—O2—O2^xiii	124.4 (3)
O2^i—Sn1—O2^ii	98.1 (2)	O2^x—O2—O2^xvii	90.0 (2)
N2—Ge1—N2^iii	110.9 (2)	O2^x—O2—N1^xviii	62.26 (11)
N2—Ge1—N2^iv	110.9 (3)	O2^x—O2—N1	122.26 (19)
N2—Ge1—N1	108.0 (2)	O2^x—O2—N1^xiv	58.85 (19)
N2^iii—Ge1—N2^iv	110.9 (3)	O2^xi—O2—O2^xiii	90.0 (2)
N2^iii—Ge1—N1	108.0 (2)	O2^xi—O2—O2^xvii	124.4 (3)
N2^iv—Ge1—N1	108.0 (2)	O2^xi—O2—N1^xviii	122.26 (19)
Ge2^i—Ge2—Ge2^v	180	O2^xi—O2—N1	62.26 (11)
Ge2^i—Ge2—Ge2^ii	60	O2^xi—O2—N1^xiv	58.85 (19)
Ge2^i—Ge2—Ge2^vi	120	O2^xiii—O2—O2^xvii	68.8 (2)
Ge2^i—Ge2—N2	87.94 (13)	O2^xiii—O2—N1^xviii	123.8 (3)
Ge2^i—Ge2—N2^i	43.80 (19)	O2^xiii—O2—N1	55.03 (19)
Ge2^i—Ge2—N2^vii	136.20 (12)	O2^xiii—O2—N1^xiv	65.6 (2)
Ge2^i—Ge2—N2^viii	92.06 (16)	O2^xvii—O2—N1^xviii	55.03 (19)
Ge2^i—Ge2—O1	138.97 (13)	O2^xvii—O2—N1	123.8 (3)
Ge2^i—Ge2—O1^ix	41.03 (13)	O2^xvii—O2—N1^xiv	65.6 (2)
Ge2^v—Ge2—Ge2^ii	120	N1^xviii—O2—N1	175.4 (2)
Ge2^v—Ge2—Ge2^vi	60	N1^xviii—O2—N1^xiv	91.61 (18)
Ge2^v—Ge2—N2	92.06 (13)	N1—O2—N1^xiv	91.61 (18)
Ge2^v—Ge2—N2^i	136.20 (19)	Ge2—O1—Ge2^v	97.9 (3)
Ge2^v—Ge2—N2^vii	43.80 (12)	Ge2—O1—Ge2^vi	97.9 (3)
Ge2^v—Ge2—N2^viii	87.94 (16)	Ge2—O1—N2	43.42 (12)
Ge2^v—Ge2—O1	41.03 (13)	Ge2—O1—N2^xix	141.0 (2)
Ge2^v—Ge2—O1^ix	138.97 (13)	Ge2—O1—N2^i	43.42 (13)
Ge2^ii—Ge2—Ge2^vi	180	Ge2—O1—N2^v	141.0 (3)
Ge2^ii—Ge2—N2	43.80 (12)	Ge2—O1—N2^vi	93.60 (14)
Ge2^ii—Ge2—N2^i	87.9 (3)	Ge2—O1—N2^iv	93.60 (14)
Ge2^ii—Ge2—N2^vii	92.06 (17)	Ge2—O1—N2^xx	97.6 (3)
Ge2^ii—Ge2—N2^viii	136.20 (19)	Ge2—O1—N2^vii	49.13 (17)
Ge2^ii—Ge2—O1	138.97 (13)	Ge2—O1—N2^viii	49.1 (2)
Ge2^ii—Ge2—O1^ix	41.03 (13)	Ge2^v—O1—Ge2^vi	97.9 (3)
Ge2^vi—Ge2—N2	136.20 (12)	Ge2^v—O1—N2	93.60 (14)
Ge2^vi—Ge2—N2^i	92.1 (3)	Ge2^v—O1—N2^xix	93.60 (14)
Ge2^vi—Ge2—N2^vii	87.94 (17)	Ge2^v—O1—N2^i	141.0 (3)
Ge2^vi—Ge2—N2^viii	43.80 (19)	Ge2^v—O1—N2^v	43.42 (13)
Ge2^vi—Ge2—O1	41.03 (13)	Ge2^v—O1—N2^vi	141.0 (2)
Ge2^vi—Ge2—O1^ix	138.97 (13)	Ge2^v—O1—N2^iv	43.42 (12)
N2—Ge2—N2^i	86.6 (3)	Ge2^v—O1—N2^xx	49.13 (18)
N2—Ge2—N2^vii	93.4 (3)	Ge2^v—O1—N2^vii	49.13 (18)
N2—Ge2—N2^viii	180	Ge2^v—O1—N2^viii	97.6 (3)
N2—Ge2—O1	95.47 (19)	Ge2^vi—O1—N2	141.0 (2)
N2—Ge2—O1^ix	84.53 (19)	Ge2^vi—O1—N2^xix	43.42 (12)
N2^i—Ge2—N2^vii	180	Ge2^vi—O1—N2^i	93.60 (16)
N2^i—Ge2—N2^viii	93.4 (3)	Ge2^vi—O1—N2^v	93.60 (17)
N2^i—Ge2—O1	95.5 (3)	Ge2^vi—O1—N2^vi	43.42 (12)
N2^i—Ge2—O1^ix	84.5 (3)	Ge2^vi—O1—N2^iv	141.0 (2)
N2^vii—Ge2—N2^viii	86.6 (3)	Ge2^vi—O1—N2^xx	49.13 (18)
N2^vii—Ge2—O1	84.53 (19)	Ge2^vi—O1—N2^vii	97.6 (3)
N2^vii—Ge2—O1^ix	95.47 (19)	Ge2^vi—O1—N2^viii	49.1 (2)
N2^viii—Ge2—O1	84.5 (2)	N2—O1—N2^xix	170.5 (3)
N2^viii—Ge2—O1^ix	95.5 (2)	N2—O1—N2^i	56.5 (2)
O1—Ge2—O1^ix	180	N2—O1—N2^v	119.4 (2)
Ge3^x—Ge3—Ge3^iii	180	N2—O1—N2^vi	119.41 (19)
Ge3^x—Ge3—Ge3^xi	60	N2—O1—N2^iv	63.08 (19)
Ge3^x—Ge3—Ge3^iv	120	N2—O1—N2^xx	126.1 (3)
Ge3^x—Ge3—O2	41.12 (15)	N2—O1—N2^vii	63.33 (17)
Ge3^x—Ge3—O2^xi	87.05 (12)	N2—O1—N2^viii	92.5 (3)
Ge3^x—Ge3—O2^xii	138.88 (15)	N2^xix—O1—N2^i	119.4 (2)
Ge3^x—Ge3—O2^xiii	92.95 (12)	N2^xix—O1—N2^v	63.1 (2)
Ge3^x—Ge3—N1	137.11 (13)	N2^xix—O1—N2^vi	56.53 (18)
Ge3^x—Ge3—N1^xiv	42.89 (13)	N2^xix—O1—N2^iv	119.41 (19)
Ge3^iii—Ge3—Ge3^xi	120	N2^xix—O1—N2^xx	63.3 (2)
Ge3^iii—Ge3—Ge3^iv	60	N2^xix—O1—N2^vii	126.1 (3)
Ge3^iii—Ge3—O2	138.88 (15)	N2^xix—O1—N2^viii	92.5 (3)
Ge3^iii—Ge3—O2^xi	92.95 (12)	N2^i—O1—N2^v	170.5 (3)
Ge3^iii—Ge3—O2^xii	41.12 (15)	N2^i—O1—N2^vi	63.1 (2)
Ge3^iii—Ge3—O2^xiii	87.05 (12)	N2^i—O1—N2^iv	119.4 (2)
Ge3^iii—Ge3—N1	42.89 (13)	N2^i—O1—N2^xx	126.1 (3)
Ge3^iii—Ge3—N1^xiv	137.11 (13)	N2^i—O1—N2^vii	92.5 (2)
Ge3^xi—Ge3—Ge3^iv	180	N2^i—O1—N2^viii	63.33 (18)
Ge3^xi—Ge3—O2	87.05 (15)	N2^v—O1—N2^vi	119.4 (2)
Ge3^xi—Ge3—O2^xi	41.12 (14)	N2^v—O1—N2^iv	56.5 (2)
Ge3^xi—Ge3—O2^xii	92.95 (15)	N2^v—O1—N2^xx	63.33 (16)
Ge3^xi—Ge3—O2^xiii	138.88 (14)	N2^v—O1—N2^vii	92.5 (2)
Ge3^xi—Ge3—N1	137.11 (13)	N2^v—O1—N2^viii	126.1 (3)
Ge3^xi—Ge3—N1^xiv	42.89 (13)	N2^vi—O1—N2^iv	170.5 (3)
Ge3^iv—Ge3—O2	92.95 (15)	N2^vi—O1—N2^xx	92.5 (2)
Ge3^iv—Ge3—O2^xi	138.88 (14)	N2^vi—O1—N2^vii	126.1 (3)
Ge3^iv—Ge3—O2^xii	87.05 (15)	N2^vi—O1—N2^viii	63.3 (2)
Ge3^iv—Ge3—O2^xiii	41.12 (14)	N2^iv—O1—N2^xx	92.5 (2)
Ge3^iv—Ge3—N1	42.89 (13)	N2^iv—O1—N2^vii	63.3 (2)
Ge3^iv—Ge3—N1^xiv	137.11 (13)	N2^iv—O1—N2^viii	126.1 (3)
O2—Ge3—O2^xi	89.2 (2)	N2^xx—O1—N2^vii	62.8 (3)
O2—Ge3—O2^xii	180	N2^xx—O1—N2^viii	62.8 (2)
O2—Ge3—O2^xiii	90.8 (2)	N2^vii—O1—N2^viii	62.8 (3)
O2—Ge3—N1	96.0 (2)	Ge1—N1—Ge3	122.22 (19)
O2—Ge3—N1^xiv	84.0 (2)	Ge1—N1—Ge3^iii	122.22 (19)
O2^xi—Ge3—O2^xii	90.8 (2)	Ge1—N1—Ge3^iv	122.22 (19)
O2^xi—Ge3—O2^xiii	180	Ge1—N1—O2	90.32 (19)
O2^xi—Ge3—N1	96.04 (19)	Ge1—N1—O2^xxi	90.32 (19)
O2^xi—Ge3—N1^xiv	83.96 (19)	Ge1—N1—O2^i	90.32 (19)
O2^xii—Ge3—O2^xiii	89.2 (2)	Ge1—N1—O2^iii	90.32 (19)
O2^xii—Ge3—N1	84.0 (2)	Ge1—N1—O2^xi	90.32 (19)
O2^xii—Ge3—N1^xiv	96.0 (2)	Ge1—N1—O2^iv	90.32 (19)
O2^xiii—Ge3—N1	83.96 (19)	Ge1—N1—O2^xii	143.32 (16)
O2^xiii—Ge3—N1^xiv	96.04 (19)	Ge1—N1—O2^xiii	143.32 (16)
N1—Ge3—N1^xiv	180	Ge1—N1—O2^xxii	143.32 (16)
Sn1—N2—Ge1	119.5 (3)	Ge3—N1—Ge3^iii	94.2 (3)
Sn1—N2—Ge2	96.7 (3)	Ge3—N1—Ge3^iv	94.2 (3)
Sn1—N2—Ge2^ii	96.68 (17)	Ge3—N1—O2	41.26 (12)
Sn1—N2—N2^i	50.3 (2)	Ge3—N1—O2^xxi	135.4 (3)
Sn1—N2—N2^ii	50.32 (17)	Ge3—N1—O2^i	91.74 (14)
Sn1—N2—N2^xv	139.60 (18)	Ge3—N1—O2^iii	91.74 (14)
Sn1—N2—N2^vii	139.6 (4)	Ge3—N1—O2^xi	41.26 (12)
Sn1—N2—O1^xvi	94.20 (16)	Ge3—N1—O2^iv	135.4 (3)
Sn1—N2—O1	94.2 (3)	Ge3—N1—O2^xii	47.13 (15)
Sn1—N2—O1^ix	95.5 (3)	Ge3—N1—O2^xiii	47.13 (17)
Ge1—N2—Ge2	122.44 (19)	Ge3—N1—O2^xxii	94.5 (3)
Ge1—N2—Ge2^ii	122.4 (4)	Ge3^iii—N1—Ge3^iv	94.2 (3)
Ge1—N2—N2^i	145.5 (3)	Ge3^iii—N1—O2	135.4 (3)
Ge1—N2—N2^ii	145.5 (3)	Ge3^iii—N1—O2^xxi	41.26 (12)
Ge1—N2—N2^xv	87.7 (3)	Ge3^iii—N1—O2^i	135.4 (3)
Ge1—N2—N2^vii	87.7 (2)	Ge3^iii—N1—O2^iii	41.26 (12)
Ge1—N2—O1^xvi	89.8 (3)	Ge3^iii—N1—O2^xi	91.74 (14)
Ge1—N2—O1	89.81 (13)	Ge3^iii—N1—O2^iv	91.74 (14)
Ge1—N2—O1^ix	145.0 (3)	Ge3^iii—N1—O2^xii	47.13 (15)
Ge2—N2—Ge2^ii	92.4 (2)	Ge3^iii—N1—O2^xiii	94.5 (3)
Ge2—N2—N2^i	46.7 (2)	Ge3^iii—N1—O2^xxii	47.13 (17)
Ge2—N2—N2^ii	92.1 (3)	Ge3^iv—N1—O2	91.74 (14)
Ge2—N2—N2^xv	91.3 (2)	Ge3^iv—N1—O2^xxi	91.74 (14)
Ge2—N2—N2^vii	43.3 (2)	Ge3^iv—N1—O2^i	41.26 (12)
Ge2—N2—O1^xvi	133.2 (3)	Ge3^iv—N1—O2^iii	135.4 (3)
Ge2—N2—O1	41.11 (15)	Ge3^iv—N1—O2^xi	135.4 (3)
Ge2—N2—O1^ix	46.34 (13)	Ge3^iv—N1—O2^iv	41.26 (12)
Ge2^ii—N2—N2^i	92.1 (3)	Ge3^iv—N1—O2^xii	94.5 (3)
Ge2^ii—N2—N2^ii	46.70 (18)	Ge3^iv—N1—O2^xiii	47.13 (18)
Ge2^ii—N2—N2^xv	43.30 (15)	Ge3^iv—N1—O2^xxii	47.13 (18)
Ge2^ii—N2—N2^vii	91.3 (2)	O2—N1—O2^xxi	175.44 (16)
Ge2^ii—N2—O1^xvi	41.11 (16)	O2—N1—O2^i	64.51 (15)
Ge2^ii—N2—O1	133.2 (3)	O2—N1—O2^iii	120.00 (15)
Ge2^ii—N2—O1^ix	46.34 (12)	O2—N1—O2^xi	55.48 (15)
N2^i—N2—N2^ii	60.0 (3)	O2—N1—O2^iv	120.00 (15)
N2^i—N2—N2^xv	121.4 (3)	O2—N1—O2^xii	88.39 (18)
N2^i—N2—N2^vii	90.0 (3)	O2—N1—O2^xiii	59.36 (16)
N2^i—N2—O1^xvi	121.5 (2)	O2—N1—O2^xxii	121.6 (3)
N2^i—N2—O1	61.7 (2)	O2^xxi—N1—O2^i	120.00 (15)
N2^i—N2—O1^ix	58.6 (2)	O2^xxi—N1—O2^iii	55.48 (15)
N2^ii—N2—N2^xv	90.0 (2)	O2^xxi—N1—O2^xi	120.00 (15)
N2^ii—N2—N2^vii	121.4 (3)	O2^xxi—N1—O2^iv	64.51 (15)
N2^ii—N2—O1^xvi	61.7 (2)	O2^xxi—N1—O2^xii	88.39 (18)
N2^ii—N2—O1	121.5 (3)	O2^xxi—N1—O2^xiii	121.6 (3)
N2^ii—N2—O1^ix	58.60 (19)	O2^xxi—N1—O2^xxii	59.36 (16)
N2^xv—N2—N2^vii	62.7 (2)	O2^i—N1—O2^iii	175.44 (16)
N2^xv—N2—O1^xvi	53.9 (2)	O2^i—N1—O2^xi	120.00 (15)
N2^xv—N2—O1	116.6 (3)	O2^i—N1—O2^iv	55.48 (15)
N2^xv—N2—O1^ix	62.76 (17)	O2^i—N1—O2^xii	121.6 (3)
N2^vii—N2—O1^xvi	116.6 (3)	O2^i—N1—O2^xiii	59.4 (2)
N2^vii—N2—O1	53.9 (2)	O2^i—N1—O2^xxii	88.4 (2)
N2^vii—N2—O1^ix	62.76 (19)	O2^iii—N1—O2^xi	64.51 (15)
O1^xvi—N2—O1	170.5 (3)	O2^iii—N1—O2^iv	120.00 (15)
O1^xvi—N2—O1^ix	87.45 (17)	O2^iii—N1—O2^xii	59.36 (17)
O1—N2—O1^ix	87.5 (2)	O2^iii—N1—O2^xiii	121.6 (3)
Sn1—O2—Ge3	126.3 (2)	O2^iii—N1—O2^xxii	88.4 (2)
Sn1—O2—Ge3^x	126.3 (2)	O2^xi—N1—O2^iv	175.44 (16)
Sn1—O2—O2^x	139.1 (3)	O2^xi—N1—O2^xii	59.36 (17)
Sn1—O2—O2^xi	139.1 (3)	O2^xi—N1—O2^xiii	88.4 (2)
Sn1—O2—O2^xiii	94.9 (2)	O2^xi—N1—O2^xxii	121.6 (3)
Sn1—O2—O2^xvii	94.9 (2)	O2^iv—N1—O2^xii	121.6 (3)
Sn1—O2—N1^xviii	87.87 (16)	O2^iv—N1—O2^xiii	88.4 (2)
Sn1—O2—N1	87.87 (16)	O2^iv—N1—O2^xxii	59.4 (2)
Sn1—O2—N1^xiv	155.9 (3)	O2^xii—N1—O2^xiii	62.3 (2)
Ge3—O2—Ge3^x	97.8 (3)	O2^xii—N1—O2^xxii	62.3 (2)
Ge3—O2—O2^x	92.9 (2)	O2^xiii—N1—O2^xxii	62.3 (2)
Ge3—O2—O2^xi	45.42 (15)

Symmetry codes: (i) −y, x−y+1, z; (ii) −x+y−1, −x, z; (iii) −y+1, x−y+1, z; (iv) −x+y, −x+1, z; (v) −y+1, x−y+2, z; (vi) −x+y−1, −x+1, z; (vii) x−y+2/3, −y+4/3, −z+4/3; (viii) −x−1/3, −x+y+1/3, −z+4/3; (ix) y−4/3, x+1/3, −z+4/3; (x) −y, x−y, z; (xi) −x+y, −x, z; (xii) y+1/3, x+2/3, −z+5/3; (xiii) x−y+1/3, −y+2/3, −z+5/3; (xiv) y−2/3, x−1/3, −z+5/3; (xv) y−1/3, x+1/3, −z+4/3; (xvi) x, y−1, z; (xvii) −x−2/3, −x+y−1/3, −z+5/3; (xviii) x−1, y−1, z; (xix) x, y+1, z; (xx) y−1/3, x+4/3, −z+4/3; (xxi) x+1, y+1, z; (xxii) −x+1/3, −x+y+2/3, −z+5/3.