Revisiting the hydrogenation behavior of NdGa and its hydride phases

Shtender, V.; Cedervall, J.; Ek, G.; Zlotea, C.; Andersson, M.S.; Manuel, P.; Sahlberg, M.; Häussermann, U.

doi:10.1107/S1600576724000554

research papers

JOURNAL OF
APPLIED
CRYSTALLOGRAPHY

ISSN: 1600-5767

Volume 57| Part 2| April 2024| Pages 248-257

https://doi.org/10.1107/S1600576724000554

Open

access

Revisiting the hydrogenation behavior of NdGa and its hydride phases

Vitalii Shtender,^a ^* Johan Cedervall,^a Gustav Ek,^a Claudia Zlotea,^b Mikael S. Andersson,^a Pascal Manuel,^c Martin Sahlberg ^a and Ulrich Häussermann ^d

^aDepartment of Chemistry – Ångström Laboratory, Uppsala University, Box 538, Uppsala 751 21, Sweden, ^bUniversité Paris-Est Creteil, CNRS, ICMPE, UMR 7182, 2 rue Henri Dunant, Thiais 94320, France, ^cISIS Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxford OX11 0QX, United Kingdom, and ^dDepartment of Materials and Environmental Chemistry, Stockholm University, Stockholm 106 91, Sweden
^*Correspondence e-mail: vitalii.shtender@angstrom.uu.se

Edited by A. Borbély, Ecole National Supérieure des Mines, Saint-Etienne, France (Received 2 November 2023; accepted 15 January 2024; online 16 February 2024)

NdGa hydride and deuteride phases were prepared from high-quality NdGa samples and their structures characterized by powder and single-crystal X-ray diffraction and neutron powder diffraction. NdGa with the orthorhombic CrB-type structure absorbs hydrogen at hydrogen pressures ≤ 1 bar until reaching the composition NdGaH(D)_1.1, which maintains a CrB-type structure. At elevated hydrogen pressure additional hydrogen is absorbed and the maximum composition recovered under standard temperature and pressure conditions is NdGaH(D)_1.6 with the Cmcm LaGaH_1.66-type structure. This structure is a threefold superstructure with respect to the CrB-type structure. The hydrogen atoms are ordered and distributed on three fully occupied Wyckoff positions corresponding to tetrahedral (4c, 8g) and trigonal–bipyramidal (8g) voids in the parent structure. The threefold superstructure is maintained in the H-deficient phases NaGaH(D)_x until 1.6 ≥ x ≥ 1.2. At lower H concentrations, coinciding with the composition of the hydride obtained from hydrogenation at atmospheric pressure, the unit cell of the CrB-type structure is resumed. This phase can also display H deficiency, NdGaH(D)_y (1.1 ≥ y ≥ 0.9), with H(D) exclusively situated in partially empty tetrahedral voids. The phase boundary between the threefold superstructure (LaGaH_1.66 type) and the onefold structure (NdGaH_1.1 type) is estimated on the basis of phase–composition isotherms and neutron powder diffraction to be x = 1.15.

Keywords: intermetallic compounds; metal hydrides; crystal structure; Zintl phases.

CCDC references: 2265528; 2265529; 2265530; 2265531; 2265532

1. Introduction

Zintl phases are compounds which constitute an active metal [alkali, alkaline earth (AE) or rare earth (RE)] and a more electronegative p-element component (Haussermann et al., 2011 ). Like less-polar intermetallic compounds, Zintl phases can react with hydrogen to form hydrides. Although the H content of Zintl phase hydrides is comparatively low (H/M < 1), the chemical structures and physical properties of Zintl phases can change profoundly upon H incorporation. The hydrogenation-induced metal–semiconductor transition for the systems AETt–AETtH (AE = Ba and Sr, Tt = Si, Ge, Sn and Pb) (Auer et al., 2017 ) and AETrTt–AETrTtH (Tr = Al, Ga, In; Tt = Si, Ge, Sn) (Häussermann, 2008 ) has been well investigated. More recently, interest has shifted to RE metal-containing Zintl phases because of hydrogenation-induced magnetic property changes (Werwein et al., 2018 , 2019 ; Nedumkandathil et al., 2016 ). For example, NdGa, GdGa and Eu₃Si₄ are all ferromagnetic Zintl phases which, upon H incorporation, either become antiferromagnetic [NdGa (Ångström et al., 2016 ) and GdGa (Nedumkandathil et al., 2016)] or paramagnetic (Eu₃Si₄) hydrides (Ek et al., 2019 ). Our main interest resides in the explicit elucidation of the magnetic structures of NdGa and its hydrides, i.e. hydrogen-induced magnetic property changes. However, during attempts to prepare pure samples for neutron diffraction studies of the magnetic structure we encountered some peculiarities and deviations from previous work. Consequently, in this paper we want to focus on the structural analysis and provide an updated and clear view of the hydrogenation behavior and hydride phases of NdGa.

The structures of NdGa and its hydrides have previously been studied by Dwight et al. (1967 ) who concluded that NdGa crystallizes in an orthorhombic CrB-type structure. In the first report on hydrides (and deuterides) of NdGa by Ångström et al. (2016), the hydride NdGaH_∼1.66 was produced after hydrogenation at 10–20 bar and near 573 K and a monoclinic structure was deduced from neutron powder diffraction (NPD) of its corresponding deuteride. In the NdGaH_1.66 structure the arrangement of the metal atoms of the NdGa Zintl-phase precursor is essentially maintained while H is incorporated into two distinct positions: a fully occupied tetrahedral void defined by four Nd atoms and a partially occupied (66%) trigonal–bipyramidal void defined by three Nd and two Ga atoms. It was further shown that H desorption from NdGaH_1.66 occurs in two discrete steps that correlate with the two types of H position. Later, Auer et al. (2019 ) studied the formation of NdGaD_x by in situ NPD and concluded that the structure of NdGaH_1.66 is an orthorhombic threefold superstructure of the CrB-type structure of the parent compound NdGa, with H atoms ordered on three fully occupied positions. In addition, Auer et al. (2019) found evidence of twofold superstructuring for lower H concentrations, 1.53 < x < 1.66, whereas phases with H compositions 1.10 < x < 1.22 attained the cell of the CrB-type structure and hydrides with H contents lower than NdGaH_x (x < 1) were not reported.

In the previous reports on NdGa hydrides the authors have experienced difficulties with preparing impurity-free NdGa samples (Auer et al., 2019; Ångström et al., 2016). The presence of impurities can impede the structure characterization of hydrides from powder diffraction and may also lead to misinterpretation of magnetic properties from magnetometry measurements. In this article we report on the synthesis of (virtually) phase-pure and single-crystalline NdGa and NdGaH(D)_x hydrides/deuterides (x = 0.9, 1.1, 1.2 and 1.6). The single-crystal nature and the phase purity of the samples allowed for more accurate structure refinements and a more reliable analysis of the superstructure phenomenon.

2. Experiment

2.1. Synthesis

NdGa was synthesized by arc melting pieces of pure Nd (Smart-elements, purity 99.9%) and Ga (99.999%) in an Ar atmosphere (99.999%) with several remelts. A 1% excess of Nd was used to avoid the presence of NdGa₂ impurities. The sample was wrapped in Ta foil, sealed in a stainless steel tube under Ar, annealed at 1173 K for 5 d and quenched in cold water. The sample was then crushed, and small single crystals were manually collected from this powder. The powder and the single crystals were used for further characterization.

Hydrides and deuterides were synthesized similarly to previous work (Auer et al., 2019; Ångström et al., 2016). For the hydrogenation, coarse pieces of the sample were loaded into a stainless steel autoclave. Prior to the actual hydrogenation an activation procedure at 573 K in a vacuum was performed. The hydrogenation was started at 573 K and small portions of H₂ (steps of 0.2–0.5 bar) were introduced into the autoclave. This procedure is needed to avoid hydrogen-induced disproportionation of NdGa, since the kinetics of absorption are fast at the beginning. This procedure also prevents the formation of any NdH_x as observed for other RE-rich compounds (Shtender et al., 2015 ). After the active absorption at 573 K had finished, the temperature was lowered to room temperature and the H₂ pressure was increased to 25 bar. The absorption process was considered complete when no obvious pressure changes could be observed after waiting for a couple of hours. Pressure–composition isotherms (PCIs) were measured in an in-house-built Sieverts-type instrument with thermostatically calibrated volumes at 298 K. Several coarse pieces of the sample were placed inside a stainless steel sample holder and activated by a heat treatment at 573 K under a dynamic vacuum for 6 h. The temperature was maintained at 573 K, and small doses of gaseous hydrogen were introduced to avoid hydrogen-induced disproportionation, as explained above. For the calculation of the hydrogen capacity, the real equation of state for hydrogen was used from the program GASPAK (Version 3.32; Cryodata Inc., Boulder, Colorado, USA). This apparatus was also used to prepare NdGaH_x samples with x = 1.1, 1.2 and 1.6 at 1 bar and room temperature. The NdGaH(D)_x single crystals were collected from the hydrogenated powder in a similar manner to the parent compound.

2.2. Thermal desorption experiments

The thermal desorption of NdGaH_1.6 and NdGaD_1.6 was studied by simultaneous differential scanning calorimetry (DSC). A small quantity (10–20 mg) of powder was placed into an Al₂O₃ crucible which was purged three times with Ar (99.999%). The desorption experiments were performed by heating the sample to 873 K in an Ar atmosphere at a heating rate of 20 K min⁻¹. The same protocol was used to estimate the formation temperature for the NdGa compound.

Thermal desorption spectrometry (TDS) experiments were conducted on fully saturated hydrides and deuterides (up to 873 K at a heating rate of 10 K min⁻¹) to measure the hydrogen/deuterium desorption profiles with temperature. Samples with intermediate hydrogen concentrations were prepared by partial desorption using TDS and DSC instruments (by heating to specific temperatures, e.g. 473, 523, 548, 573 and 648 K) for ex situ single-crystal X-ray diffraction. NdGaD_0.9 deuteride for NPD diffraction was prepared by desorption of a fully saturated sample with the TDS technique by heating up to 648 K.

Thermal desorption from the fully saturated hydride was also studied with in situ synchrotron radiation powder X-ray diffraction (SRPXRD) on the P02.1 beamline at PETRA III at the German Electron Synchrotron (DESY, Hamburg, Germany) using a Varex XRD 4343CT detector, a sample-to-detector distance of 1150 mm and a fixed wavelength of 0.20734 Å as determined by an LaB₆ standard. The powder was loaded into a quartz tube mounted on a gas cell as described previously (Höglin et al., 2015 ; Jensen et al., 2010 ) and heated under vacuum at 10 K min⁻¹ using a filament wrapped around the quartz tube. In addition, SRPXRD patterns for NdGa, NdGaD_0.9, NdGaH_1.1, NdGaH_1.2 and NdGaH_1.6 were collected at room temperature (this was done to eliminate the strong preferred orientation present for the in-house diffractometer). The data were integrated using the software Dawn (Filik et al., 2017 ). Unit-cell parameters were extracted by sequential Pawley refinements in the software TOPAS (Version 6; Coelho, 2018 ) with the background described by a fifth-order Chebyschev polynomial and peak shapes by Thompson–Cox–Hastings pseudo-Voigt functions.

2.3. Phase analysis

The phase purity of the NdGa samples was checked with powder X-ray diffraction (PXRD) and a scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy (EDS) detector. The powders were mounted on single-crystal Si sample holders and X-ray diffraction patterns were collected using a Bruker D8 Advance with Cu Kα radiation at room temperature. The Rietveld method (Rietveld, 1969 ) as implemented in TOPAS (Version 6; Coelho, 2018) was used for analysis of the diffraction data. The samples for electron microscopy analysis were prepared by standard metallographic techniques by grinding with SiC paper. For qualitative determination of the impurity, X-ray photoelectron spectroscopy (XPS) data were collected using a PHI Quantera II system with an Al Kα X-ray source and a hemispherical electron energy analyzer having a pass energy of 26.00 eV. Before recording an XPS spectrum the sample surface was cleaned by 500 eV Ar-ion sputtering for 30 s.

For all samples, single crystals were analyzed. A Bruker D8 single-crystal X-ray diffractometer with Mo Kα radiation (λ = 0.71073 Å) upgraded with an Incoatec Microfocus Source (IμS) and an APEXII CCD area detector was utilized to collect single-crystal X-ray diffraction (SCXRD) patterns at room temperature. The SCXRD data reduction and numerical absorption corrections were performed using SADABS (Krause et al., 2015 ) as implemented in the APEX3 software (Bruker, 2016 ). Initial models of the crystal structures were first obtained with the program SHELXT2019 (Sheldrick, 2015a ) and refined using the program SHELXL2019 (Sheldrick, 2015b ) within the APEX3 software package.

Neutron powder diffraction (NPD) patterns of the deuterides (NdGaD_0.9 and NdGaD_1.6) were collected using the instrument WISH at the ISIS Neutron and Muon Source (Didcot, UK) (Chapon et al., 2011 ). Around 3 g of each sample were placed in separate V cans and measured at 20 K. The obtained diffraction data were analyzed using the Rietveld method (Rietveld, 1969) implemented in the software FULLPROF (Rodriguez-Carvajal et al., 1999 ). The deuterium positions were determined using difference Fourier maps. In the refinements several structure parameters, including the atomic positions, atomic displacement and D occupancies, were allowed to vary.

3. Results and discussion

3.1. Synthesis of (nearly) phase-pure NdGa and its hydrogenation/desorption behavior

Some available phase diagrams of the Nd–Ga system (Villars et al., 2018 ) report that the binary NdGa compound forms from the peritectic reaction of NdGa₂ and melt at around 1173 K (Okamoto, 1990 ; Manory et al., 1978 ). Thus, the synthesis of NdGa is typically performed by arc melting stoichiometric amounts of elemental metals and subsequent long annealing at temperatures below ∼1173 K, and yet the obtained NdGa products are notoriously accompanied by (unknown) impurities (Auer et al., 2019; Ångström et al., 2016). However, in the phase diagram proposed by Yatsenko et al. (1979 ) for the Nd–Ga system, the peritectic line is at a much higher temperature of 1361 K, which is in good agreement with the temperature found from our present DSC experiments (see Fig. S1 in the supporting information). Thus, higher annealing temperatures can be applied. It was found that an increase in the annealing temperature to 1173 K effectively removes the unknown impurities. It was also found that the purity of the Nd metal plays a very important role in the synthesis of high-quality NdGa samples (it should not be lower than 99.9%) and Nd should be strictly handled in an Ar-filled glove box to avoid oxidation. As a result, the NdGa alloy was synthesized with a much higher purity than in the previous reports, although the samples were still contaminated with up to ∼1.5 wt% of Nd_1−xCe_xO_1.75 (Ce is a common impurity in Nd and its presence was found by EDS). Another impurity was observed from XPS which detected peaks related to Ta (for EDS the Ta peaks are hidden in the background). Rietveld refinements of the PXRD data for NdGa, presented in Fig. 1(a), revealed the presence of ∼0.5 wt% TaGaO₄ (most probably due to the synthesis in Ta foil). Fig. 1 also presents Rietveld refinements of PXRD data for the two hydrides NdGaH_0.9 and NdGaH_1.6. As shown in Fig. S2, our NdGa sample consisted of crystals with sizes ranging from 20 to 150 µm, and EDS analysis of the crystals gives an average composition of Nd_1.02 (1)Ga_0.98 (1), confirming that stoichiometric NdGa was synthesized.

Figure 1
Rietveld refinement for the SRPXRD data profiles for NdGaH_x (x = 0, 0.9 and 1.6) compounds. The insets show the absence and presence of the 3a superlattice peaks for x = 0.9 and x = 1.6, respectively. In panel (a), 1 stands for 98% NdGa, 2 is 1.5% Nd_1−xCe_xO_1.75 and 3 is 0.5% TaGaO₄.

PCIs recorded at 573 K with H₂ [Fig. 2(a)] confirmed the results from previous work: NdGa behaves as a hydrogen getter (i.e. it absorbs H without overpressure) until a composition of NdGaH_1.1 is reached at around 1 bar. At 20 bar a hydrogen capacity of 1.56 H per formula unit (f.u.) is observed. Using the same conditions, Ångström et al. (2016) reported a limiting composition of NdGaH₂ after 48 h. Auer et al. (2019) obtained 1.8 D f.u.⁻¹ at 40 bar and 473 K in their in situ NPD study. However, compositions with >1.65 H f.u.⁻¹ can only be observed in situ (i.e. at H₂ pressure). The maximum H content in recovered NdGa hydride (under standard temperature and pressure conditions) has been consistently reported as ∼1.6 H f.u.⁻¹ and henceforth this phase is termed NdGaH(D)_1.6. The TDS and DSC results presented in Fig. 2(b) suggest a `two-step' desorption process for NdGaH_1.6 with maximum desorption rates at ∼523 and ∼723 K as proposed by Ångström et al. (2016). The temperature discrepancies between the two methods can be attributed to the fact that the TDS experiments were performed in a vacuum while the DSC experiments were done using an Ar atmosphere for which partial oxidation at higher temperatures might occur. The doublet feature of the first TDS peak is seen for both the hydride and the deuteride sample and appears to be independent of the heating rate (Ångström et al., 2016). This phenomenon will be addressed in more detail in the next section. The large temperature separation between the two desorption steps suggests that it should be possible to prepare the distinct monohydride phase NdGaH.

Figure 2
(a) PCI curves for NdGa at 573 K. (b) Combined TDS and DSC curves for NdGaH_1.6.

Interestingly, the single-crystalline nature of the Zintl-phase starting material is preserved after both hydrogenation and desorption for both the hydrides and the deuterides (Fig. S2), allowing conclusive SCXRD studies of both fully hydrogenated and partially desorbed samples. As previously described, the NPD study by Auer et al. (2019) found evidence of a threefold superstructure for NaGaD_1.6 at 480 K and 98 bar D₂ pressure, which corresponds to the LaGaH_1.66 structure. From the PXRD and SCXRD patterns presented in Figs. 1(c) and 3 for NdGaH_1.6, it can be concluded that this superstructure is maintained under ambient conditions. Thus, the monoclinic structure originally put forward for NdGaH(D)_1.6 by Ångström et al. (2016) can be ruled out.

Figure 3
Reconstructed reflections seen for a single crystal of NdGaH_1.6. The size and color of the dots are correlated with the intensities. The circled reflections represent the CrB-type structure. As can be seen, in between two strong lines (with circles) there are two weaker lines of superstructure reflections related to the threefold structure.

In order to examine whether there are distinct intermediate hydride phases, as suggested by Auer et al. (2019), several controlled desorption experiments were performed using both DSC (Ar atmosphere, for hydrides) and TDS (vacuum, for deuterides) at various temperatures. The selection of temperatures for these experiments was based on the TDS peak evolution presented in Fig. 2(b). Desorption experiments up to 648 K in a dynamic vacuum, as described in the Experiment section, aimed at complete removal of the H atoms within the trigonal–bipyramidal Nd₃Ga₂ environment to produce the distinct stoichiometric phase NdGaH(D) [which was not achieved in the desorption experiment at 493 K by Auer et al. (2019)]. However, the hydrogen compositions of products obtained by partial desorption are uncertain and further characterization is needed to determine the hydrogen (deuterium) content. The NPD experiment on the sample NdGaD_x prepared by desorption of NdGaD_1.6 to 648 K revealed that the true composition is NdGaD_0.9 and, on the basis of this result, it was assumed that the hydrogenated sample synthesized under identical conditions has the same composition. A more detailed analysis of the NPD results is presented in Section 3.3. To produce accurate compositions in the concentration range 1 < x < 1.6, NdGaH_1.1 and NdGaH_1.2 were synthesized in a Sievert-type apparatus acquiring PCI curves at low equilibrium pressures.

3.2. Crystal structure variations as a function of H content

Fig. 4 shows the crystal structures and summarizes the results from SCXRD experiments for NdGa, NdGaH_0.9, NdGaH_1.1, NdGaH_1.2 and NdGaH_1.6 (for which the H concentrations can be considered more or less reliable as discussed above). Details for the SCXRD-determined structures are presented in Tables 1 and 2.

Table 1
Crystallographic data and experimental details of the structure determination for NdGaH_x (x = 0–1.6) by single-crystal diffraction

Experiments were carried out at 296 K with Mo Kα radiation. All compounds were found to have an orthorhombic structure with space group Cmcm (No. 63).

Empirical formula	NdGa	NdGaH_0.9	NdGaH_1.1	NdGaH_1.2	NdGaH_1.6
CSD reference	2265528	2265531	2265532	2265530	2265529
Pearson symbol, Z	oC8, 4	oC8, 4	oC8, 4	oC24, 12	oC24, 12
a (Å)	4.4329 (12)	4.1855 (6)	4.1600 (3)	12.3380 (6)	12.332 (2)
b (Å)	11.246 (3)	11.914 (2)	12.0374 (9)	12.2710 (9)	12.264 (2)
c (Å)	4.1735 (11)	4.1857 (6)	4.1825 (3)	4.1691 (2)	4.1782 (7)
V (Å³)	208.1 (1)	208.7 (1)	209.44 (3)	631.2 (1)	631.9 (2)
Calculated density ρ (g cm⁻³)	6.83	6.81	6.79	6.75	6.75
Absorption coefficient μ (mm⁻¹)	37.10	36.99	36.86	36.69	36.65
θ range for data collection (°)	3.623–31.719	3.420–31.609	3.385–32.069	2.341–32.472	2.342–39.415
F(000)	364	364	364	1092	1092
Range in hkl	−6 ≤ h ≤ 6	−5 ≤ h ≤ 6	−6 ≤ h ≤ 5	−18 ≤ h ≤ 18	−21 ≤ h ≤ 21
	−15 ≤ k ≤ 16	−17 ≤ k ≤ 16	−17 ≤ k ≤ 17	−18 ≤ k ≤ 14	−21 ≤ k ≤ 21
	−6 ≤ l ≤ 6	−6 ≤ l ≤ 6	−6 ≤ l ≤ 6	−6 ≤ l ≤ 5	−7 ≤ l ≤ 7
Total No. of reflections	2217	1820	1779	7143	7329
No. of independent reflections	220 (R_eq = 0.0296)	221 (R_eq = 0.0147)	227 (R_eq = 0.0289)	635 (R_eq = 0.0572)	1070 (R_eq = 0.0306)
No. of reflections with I > 2σ(I)	187 (R_sigma = 0.0180)	220 (R_sigma = 0.0091)	214 (R_sigma = 0.0182)	511 (R_sigma = 0.0325)	919 (R_sigma = 0.0217)
Data/parameters	220/10	221/9	227/9	635/21	1070/21
Goodness of fit on F²	1.107	1.293	1.251	1.063	1.080
Final R indices [I > 2σ(I)]	R₁ = 0.0147	R₁ = 0.0105	R₁ = 0.0156	R₁ = 0.0276	R₁ = 0.0295
Final R indices [I > 2σ(I)]	wR₂ = 0.0193	wR₂ = 0.0256	wR₂ = 0.0308	wR₂ = 0.0510	wR₂ = 0.0651
R indices (all data)	R₁ = 0.0225	R₁ = 0.0107	R₁ = 0.0179	R₁ = 0.0470	R₁ = 0.0376
R indices (all data)	wR₂ = 0.0193	wR₂ = 0.0257	wR₂ = 0.0317	wR₂ = 0.0567	wR₂ = 0.0683

Table 2
Atomic coordinates and equivalent isotropic displacement parameters for NdGaH_x (x = 0–1.6) from SCXRD at 296 K

Atom	Site	x	y	z	U_eq × 100 (Å²)
NdGa
Nd	4c	0	0.35806 (3)	1/4	1.02 (1)
Ga	4c	0	0.07009 (6)	1/4	1.13 (1)

NdGaH_0.9
Nd	4c	0	0.34572 (2)	1/4	0.77 (1)
Ga	4c	0	0.05794 (4)	1/4	1.14 (1)

NdGaH_1.1
Nd	4c	0	0.34524 (3)	1/4	0.71 (1)
Ga	4c	0	0.05698 (7)	1/4	1.00 (1)

NdGaH_1.2
Nd1	4c	0	0.33415 (5)	1/4	0.71 (2)
Nd2	8g	0.32999 (3)	0.35426 (3)	1/4	0.73 (1)
Ga1	4c	0	0.05939 (10)	1/4	0.83 (3)
Ga2	8g	0.34928 (7)	0.05844 (7)	1/4	0.96 (2)

NdGaH_1.6
Nd1	4c	0	0.33632 (3)	1/4	0.63 (1)
Nd2	8g	0.33074 (2)	0.35288 (2)	1/4	0.60 (1)
Ga1	4c	0	0.05919 (7)	1/4	0.78 (2)
Ga2	8g	0.34675 (6)	0.05837 (6)	1/4	0.99 (1)

Figure 4
Crystal structures of (left) NdGa and (middle to right) its hydride phases NdGaH_1.6−x (x < 0.5), NdGaH_y (1 < y < 1.15) and NdGaH_y (y < 1), respectively. Nd and Ga atoms are depicted as gray and red circles, respectively. H atoms and their metal coordination polyhedra are represented in green (trigonal–bipyramidal interstitial) and teal (tetrahedral interstitial). Light green indicates partial occupancy. Formation conditions for the hydride phases are indicated as arrows.

The crystal structure of the Zintl-phase NdGa features polyanionic zigzag chains of Ga atoms, which are formally in a reduced Ga³⁻ state and thus singly bonded, while carrying two lone electron pairs that are hosted in the p_x and sp² orbitals. The chains run along the crystallographic c direction and are embedded in slabs of trigonal prisms formed by the Nd atoms which run along the a direction (Hyde & Andersson, 1989 ). The two types of voids for H, tetrahedral H@Nd₄ and trigonal–bipyramidal H@Nd₃Ga₂, are 4c (0, ∼¾, ¼) and 4c (0, ∼0.55, ¼), respectively.

Hydrogenation of NdGa at pressures above 20 bar results in the formation of NdGaH_1.6, where the a axis of the initial CrB-type structure is tripled (a = 3a_CrB) while the Cmcm space group type symmetry is maintained. The tetrahedral voids of the CrB-type structure are completely filled (positions H1 and H2 in Fig. 4) and two-thirds of the trigonal–bipyramidal voids are filled in an orderly fashion (position H3 in Fig. 4). The b lattice parameter of NdGaH_1.6 is increased by 9% compared with that of NdGa [from 11.246 (3) to 12.264 (2) Å], whereas a/3 is decreased by 1.8% (from 4.186 to 4.111 Å) and the c parameter (i.e. along the direction of the Ga chains) is hardly influenced (∼4.17 Å, cf. Table 2). As a consequence, the volume per formula unit (V/Z) increases by just 1%, from 52.1 to 52.6 Å³. Remarkably, the lattice parameters (and volume) of NdGaH_1.2 are very similar to those of NdGaH_1.6, as can be seen in Fig. 5(a), which presents a comparison of the volumes of the different phases (x = 0, 0.9, 1.1, 1.2 and 1.6). Below 1.2 H f.u.⁻¹ hydrogenated NdGa adopts the CrB-type structure (i.e. the 1a structure). The evolution of the PXRD patterns from 1.6 to 0.9 H f.u.⁻¹ is presented in Fig. 5(b) which, together with Fig. 5(a), provides insights into the boundaries between the different structures. For NdGaH_1.1 the 3a superstructure reflections are absent, while the main reflections appear significantly broadened. Refinement of the PXRD pattern as a two-phase mixture (Fig. S3) gives slightly improved discrepancy values (R_wp), indicating heterogeneity of the NdGaH_1.1 sample. We note that the NdGaH_1.1 phase obtained by PCI at low pressure compares well to the NdGaD_1.11 phase obtained by Auer et al. (2019) from desorption of NdGaD_1.6 at 493 K (1 h, vacuum). The lattice parameters are also comparable: a = 4.1656 (3) Å, b = 12.0336 (9) Å and c = 4.1858 (2) Å for NdGaH_1.1 versus a = 4.1600 (3) Å, b = 12.0374 (9) Å and c = 4.1825 (3) Å for NdGaD_1.11. However, the PXRD and SCXRD data show no evidence of the 2a superstructure as proposed by Auer et al. (2019). The boundary for the 1a–3a structural change is assumed to be around 1.15 H f.u.⁻¹.

Figure 5
(a) V/Z versus H f.u.⁻¹ for hydrides with known H content. (b) A comparison of patterns, with broader peaks for NdGaH_1.1. The labels 420 and 421 are superstructure reflections, arrows show broadened peaks, and the asterisk (*) indicates the impurity of TaGaO₄.

Fig. 6(a) summarizes the results from the desorption experiments where the thermal desorption spectra of NdGaH_1.6, NdGaH_1.2, NdGaH_1.1 and NdGaD_0.9 are compared. As already mentioned, the first peak in the spectrum of NdGa_1.6 exhibits a doublet feature which is present for both samples where only the threefold supercell structure of the hydride is present. However, NdGaH_1.1 does not exhibit any clear doublet feature even though a desorption event is still present in this temperature region. The TDS spectrum for NdGaD_0.9, which has the 1a structure, exhibits a single desorption step in the same temperature range as the second desorption step for NdGaH_1.6, NdGaH_1.2 and NdGaH_1.1. The SCXRD, PXRD and TDS data together suggest that the first peak is associated with desorption of H from the trigonal–bipyramidal interstitials, while the second peak is associated with desorption from the tetrahedral interstitials. Consequently, the doublet feature mirrors a two-step desorption of H from the trigonal–bipyramidal interstitials, corresponding initially to desorption from the phase with the 3a superstructure until the estimated boundary at around 1.15 H f.u.⁻¹ and consecutively from the phase with the 1a structure. Additionally, one should note that the onset temperatures of desorption for the NdGaH_1.6, NdGaH_1.2 and NdGaH_1.1 samples are different, which implies higher stability of the 1a hydride structure.

Figure 6
(a) TDS spectra and (b) V/Z versus T plots showing the region where the supercell exists. NdGaH_1.1 is a two-phase sample with 1a and 3a unit cells, while NdGaH_1.6 is 3a phase sample. T = 523 K is the last temperature which results in a 3a structure, while desorption at 573 K results in a 1a structure.

Fig. 6(b) illustrates the V/Z values of phases obtained from DSC (hydrides) and TDS (deuterides) desorption experiments at various temperatures across the first and second desorption peaks. The H(D) contents of these phases are uncertain but the 648 K sample has 0.9 H(D) f.u.⁻¹, which was determined using NPD. From PXRD, the temperature boundary for the 3a–1a structural change was determined to be around 523 K [Figs. 6(a) and S4]. This coincides well with the center of the doublet feature in the TDS spectrum. Systematically larger cell volumes were observed for the hydrides than for the corresponding deuterides. However, both hydrides and deuterides exhibit similar changes in their cell parameters with respect to temperature.

A detailed study of the structural evolution during hydrogen desorption was carried out by in situ SRPXRD experiments on NdGaH_1.6 during desorption in a vacuum. A selected region of the SRPXRD map together with the V/Z data and the TDS spectrum for NdGaH_1.6 are presented in Fig. 7. From room temperature up to 473 K there is a linear increase in the volume due to thermal expansion. Above 473 K V/Z drops sharply, indicating the start of desorption, which coincides with the onset of the first desorption peak in the TDS spectrum (lower panel of Fig. 7). The superlattice reflection 421 disappears at around 493 K, accompanied by a discontinuous change in the 041 peak. This further indicates that the first peak of the doublet on the TDS curve correlates with the disappearance of the superlattice peaks due to desorption. However, the second peak of the doublet is the beginning of desorption from the saturated hydride with the 1a structure. Furthermore, at this temperature two pairs of main peaks (330 and 311, and 151 and 600) start to overlap, showing further changes in the structure (shrinking of the unit cell due to hydrogen release). Above 493 K only peaks related to the CrB-type structure are present, although they continue to change due to the ongoing desorption process. At around 773 K the two peak pairs (330 and 311, and 151 and 600) split and can once again be resolved. At around 873 K the 041 and 331 peaks start to overlap, coinciding with the end of desorption. After completion of desorption the volume increases linearly with temperature. The TDS and SRPXRD data show good agreement.

Figure 7
(Top) Selected region of the in situ SRPXRD map. The white star indicates the disappearance of the superlattice peak 421. (Bottom) V/Z with the TDS spectrum for NdGaH_1.6.

To summarize, the X-ray diffraction and desorption experiments suggest the existence of the NdGaH(D)_x (1.6 ≥ x ≥ 1.2) phase with the 3a superstructure and the NdGaH(D)_y (1.1 ≥ y ≥ 0.9) phase with the 1a structure (CrB-type structure). The compositions with y = 1.1 and 0.9 correspond to weakly occupied trigonal–bipyramidal interstitials and weakly depleted tetrahedral interstitials, respectively (Fig. 4). The 1a structured phase NdGdH_1.1 represents both the product of the initial absorption (H getter behavior of NdGa) and the product after the first desorption step.

3.3. Crystal structures of NdGaD_1.6 and NdGaD_0.9 from NPD at 20 K

To determine the H(D) positions and occupancies in NdGaH(D)_x accurately, NPD experiments were performed for two samples with nominal compositions NdGaD and NdGaD_1.6 at 20 K and ambient pressure. Rietveld refinements of the NPD data revealed that the true compositions of the samples are NdGaD_0.9 and NdGaD_1.6. The refinements of the NPD data from detector bank 3 are presented in Fig. 8 for NdGaD_0.9 and NdGaD_1.6, while the structural parameters obtained from the refinements are presented in Table 3. For NdGaD_1.6 a 3a supercell is found, as previously reported by Auer et al. (2019) for NdGaD_1.66 at 480 K and 98 bar D₂ pressure. Furthermore, the observed 3a superstructure is in good agreement with the findings from the PXRD and SCXRD results presented in Section 3.1 for NdGaH_1.6. In the superstructure there are a total of three deuterium positions, where D1 and D2 are tetrahedral interstitials while D3 is a trigonal–bipyramidal interstitial (Fig. 4). As for the PXRD and SCXRD experiments, no supercell is observed in the NPD experiment for NdGaD_0.9. This is also in good agreement with the NPD results from Auer et al. (2019), who concluded that there is no supercell for NdGaD_1.11, NdGaD_1.16 and NdGaD_1.22. However, contrary to their results which suggest that NdGaD_1.11, NdGaD_1.16 and NdGaD_1.22 have two deuterium positions, the NPD results presented here show that NdGaD_0.9 only exhibits a single deuterium position with the D atom as a tetrahedral interstitial (Fig. 4 and corresponding Fourier difference maps in Fig. S5). The discrepancy between the study by Auer and co-workers and the results presented here could be related to the presence of unidentified impurities in the samples used by (Auer et al., 2019), together with contamination of the NPD patterns from scattering from the sample environment, which probably limited their NPD analysis. Last but not least, the experimental conditions here (ex situ NPD) and in the previous work (in situ NPD) are different. Comparing the PXRD, SCXRD and NPD results, it can be concluded that in the studied temperature range neither NdGaD_0.9 nor NdGaD_1.6 exhibits any structural phase changes, suggesting that the changes from the 3a to the 1a cell are only related to the hydrogen (deuterium) content.

Table 3
Crystallographic data and structure refinement for NdGaD_0.9 and NdGaD_1.6 (both space group Cmcm, No. 63), fractional atomic coordinates, site occupancy factor (SOF) and atomic displacement parameters at 20 K

Values refer to data from WISH detector bank 3 at 2θ = 90°.

Atom	Site	x	y	z	SOF	U_eq × 100 (Å²)
NdGaD_0.9, a = 4.1736 (9) Å, b = 11.916 (3) Å, c = 4.1816 (9) Å, V = 208.0 (7) Å³ and R_Bragg = 5.38
Nd	4c	0	0.3449 (2)	1/4	1	0.45 (1)
Ga	4c	0	0.0568 (1)	1/4	1	0.65 (1)
D	4c	0	0.7485 (1)	1/4	0.91 (1)	1.7 (4)

NdGaD_1.6, a = 12.297 (3) Å, b = 12.221 (3) Å, c = 4.1619 (8) Å, V = 625.4 (5) Å³ and R_Bragg = 8.48
Nd1	4c	0	0.3550 (9)	1/4	1	1.28 (4)
Nd2	8g	0.33381 (9)	0.35211 (6)	1/4	1	0.41 (2)
Ga1	4c	0	0.0560 (1)	1/4	1	1.08 (4)
Ga2	8g	0.34728 (6)	0.06052 (8)	1/4	1	1.28 (3)
D1	4c	0	0.7498 (1)	1/4	1	3.5 (6)
D2	8g	0.1682 (1)	0.24893 (9)	1/4	1	3.0 (3)
D3	8g	0.18670 (9)	0.05154 (8)	1/4	0.890 (2)	3.5 (3)

Figure 8
Rietveld refinement of (a) NdGaD_0.9 and (b) NdGaD_1.6 from the 90° detector bank 3 at 20 K with R_wp = 6.00 and 6.03%, respectively. The bottom rows of Bragg reflections correspond to a secondary phase, TaGaO₄ (0.5%).

As mentioned above, the D atoms occupy the tetrahedral interstitials surrounded by four Nd atoms in the NdGaD_0.9 phase, while the trigonal–bipyramidal interstitial positions are empty. The D—Nd distances are close to equidistant, 2.368 (1) Å (×2) and 2.382 (1) Å (×2), i.e. the tetrahedra remain largely undistorted upon hydrogenation of the tetrahedral interstitials. The Ga—Ga distance in NdGaD_0.9 is 2.491 (1) Å at 20 K (Table 4), which is drastically reduced compared with NdGa [2.625 (1) Å at room temperature]. This reduction in the Ga—Ga distance was described earlier and is attributed to the development of π-bonding within the Ga zigzag chain. The introduction of H into the tetrahedral interstitials as H⁻ formally leads to oxidation of the singly bonded zigzag chain formed by the Ga³⁻ species, upon which the antibonding part of the π(p_x–p_x) band is emptied. A phase width of NdGaH_1±y towards hydrogen-poor compositions has previously been questioned by Auer et al. (2019). However, it appears that harsh desorption conditions, especially upon application of temperatures above 623 K, can achieve hydrogen-poor phases such as NdGaH_1−y, although the extent of this phase width is currently unknown.

Table 4
Relevant interatomic distances in NdGaD_0.9 and NdGa_1.6, T = 20 K, with estimated standard deviations in parentheses

NdGaD_0.9				NdGaD_1.6
Atom pair			d(Å)	Atom pair			d(Å)
D1	Nd1	×2	2.368 (1)	D1	Nd1	×2	2.327 (1)
D1	Nd1	×2	2.382 (1)	D1	Nd2	×2	2.396 (1)
Ga1	Ga1	×2	2.491 (1)	D2	Nd1		2.323 (1)
					Nd2		2.395 (2)
					Nd2	×2	2.420 (1)
				D3	Ga2		1.978 (1)
					Ga1		2.296 (1)
					Nd2	×2	2.404 (1)
					Nd2		2.450 (1)
				Ga1	D3	×2	2.296 (1)
				Ga1	Ga1	×2	2.490 (1)
				Ga2	D3		1.978 (1)
				Ga2	Ga2	×2	2.553 (1)

The tetrahedral environment of D in NdGaD_1.6 is more irregular than that of NdGaD_0.9, with D—Nd distances of 2.327 (1) Å (×2) and 2.396 (1) Å (×2) for D1 [average 2.362 (1) Å] and 2.323 (1) Å, 2.395 (2) Å and 2.420 (1) Å (×2) for D2 [average 2.389 (1) Å]. Most interesting is the irregular trigonal–bipyramidal environment of D3 and the different Ga—Ga distances within the zigzag chains, highlighted in Fig. 9. The ordered two-thirds occupation of the trigonal–bipyramidal voids in NdGaD_1.6 (by D3 atoms) implies two crystallographically different zigzag chains, one formed by Ga1 atoms which are coordinated by two D3 atoms (central chain) and one formed by Ga2 atoms which are only coordinated by one D3 atom (peripheral chains). The Ga—Ga distance within the central chains is 2.490 (1) Å (which is similar to that in NdGaD_0.9), while the Ga—Ga distance within the peripheral chains is substantially elongated [2.553 (1) Å]. The longest Ga—H bonds still being considered single bonds are around 1.7 Å [as in SrGa₂H₂ and AEGaTtH; AE = Ca, Sr, Ba; Tt = Si, Ge, Sn (Häussermann, 2008)], which is substantially shorter than the Ga—D3 distance in NdGaD_1.6 [Ga2—D3 = 1.978 (1) Å and Ga1—D3 = 2.296 (1) Å]. Yet a distance of 1.978 Å still suggests a covalent Ga—H bonding interaction, albeit weak, which would engage the Ga2 p_x orbital. Thus π(p_x–p_x) bonding within the peripheral zigzag chains is weakened, whereas π-bonding within the central chains remains largely unperturbed (and thus similar to that in NdGaD_0.9).

Figure 9
A segment of the NdGaD_1.6 structure, showing the coordination of D3 atoms in Nd₃Ga₂ trigonal–bipyramidal interstitials and the zigzag chains formed by Ga atoms.

There are a few more REGaH(D)_x phases reported with Cmcm 3a superstructures: GdGaH_1.66 (theoretically predicted) (Nedumkandathil et al., 2016), LaGaD_1.63 (Werwein et al., 2019) and TmGaD_0.93 (Werwein et al., 2019). For TmGaD_0.93 (Werwein et al., 2019), the trigonal–bipyramidal interstitials are not occupied by D atoms, yet a threefold superstructure is realized. Thus, further investigation of REGaH_x and especially TmGaD_0.9−x would bring a deeper understanding of the hydrides of Zintl phases as well as their hydrogen-induced property changes.

4. Conclusion

The reinvestigation of the hydrogenation behavior of orthorhombic NdGa with a Cmcm CrB-type structure and the desorption behavior of its hydrides NdGaH_x has led to the unambiguous identification of two distinct phases.

(i) NdGaH(D)_x (1.6 ≥ x ≥ 1.2) adopts the Cmcm LaGaH_1.66-type structure, which is a threefold (3a) superstructure with respect to the initial CrB-type structure. The H(D) atoms are located in fully occupied tetrahedral interstitials H@Nd₄ and flexibly occupy trigonal–bipyramidal interstitials H@Nd₃Ga₂ (0.15 < site occupancy factor ≤ 1).

(ii) NdGaH(D)_y (1.1 ≥ y ≥ 0.9) adopts the unit cell of the (1a) CrB-type structure of the parent compound NdGa. The hydrogen-rich phase presents weakly occupied trigonal–bipyramidal interstitials and fully occupied tetrahedral interstitials, while the hydrogen-poor phase exhibits no trigonal–bipyramidal interstitials and a weak depletion of the tetrahedral interstitials.

As a result of the multistep desorption occurring over a wide temperature range, these phases can be separated by partial desorption, making it possible to study in detail the hydrogen- and structure-induced property changes observed for several Zintl phases.

Supporting information

CCDC references: 2265528; 2265529; 2265530; 2265531; 2265532

Crystal structure: contains datablocks NdGa, NdGaH0.9, NdGaH1.1, NdGaH1.2, NdGaH1.6. DOI: https://doi.org/10.1107/S1600576724000554/nb5371sup1.cif

Structure factors: contains datablock NdGa. DOI: https://doi.org/10.1107/S1600576724000554/nb5371NdGasup2.hkl

Structure factors: contains datablock NdGaH0.9. DOI: https://doi.org/10.1107/S1600576724000554/nb5371NdGaH0.9sup3.hkl

Structure factors: contains datablock NdGaH1.1. DOI: https://doi.org/10.1107/S1600576724000554/nb5371NdGaH1.1sup4.hkl

Structure factors: contains datablock NdGaH1.2. DOI: https://doi.org/10.1107/S1600576724000554/nb5371NdGaH1.2sup5.hkl

Structure factors: contains datablock NdGaH1.6. DOI: https://doi.org/10.1107/S1600576724000554/nb5371NdGaH1.6sup6.hkl

Additional figures. DOI: https://doi.org/10.1107/S1600576724000554/nb5371sup7.pdf

Computing details top

(NdGa) top

Crystal data top

GaNd	D_x = 6.830 Mg m⁻³
M_r = 213.96	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 2217 reflections
a = 4.4329 (12) Å	θ = 3.6–31.7°
b = 11.246 (3) Å	µ = 37.10 mm⁻¹
c = 4.1735 (11) Å	T = 296 K
V = 208.06 (10) Å³	Needle
Z = 4	0.03 × 0.01 × 0.01 mm
F(000) = 364

Data collection top

Bruker D8 diffractometer	R_int = 0.030
Absorption correction: multi-scan SADABS	θ_max = 31.7°, θ_min = 3.6°
T_min = 0.641, T_max = 0.698	h = −6→6
2217 measured reflections	k = −15→16
220 independent reflections	l = −6→6
187 reflections with I > 2σ(I)

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: 20
R[F² > 2σ(F²)] = 0.015	w = 1/[σ²(F_o²) + (0.0044P)² + 0.5138P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.020	(Δ/σ)_max < 0.001
S = 1.11	Δρ_max = 0.93 e Å⁻³
220 reflections	Δρ_min = −1.25 e Å⁻³
10 parameters

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Nd1	0.000000	0.35806 (3)	0.250000	0.01023 (11)
Ga2	0.000000	0.07009 (6)	0.250000	0.01126 (14)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Nd1	0.00954 (14)	0.01052 (16)	0.01065 (14)	0.000	0.000	0.000
Ga2	0.0127 (3)	0.0121 (3)	0.0090 (3)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Nd1—Ga2ⁱ	3.1497 (6)	Nd1—Nd1^vii	3.8142 (10)
Nd1—Ga2ⁱⁱ	3.1497 (6)	Nd1—Nd1^viii	3.8142 (10)
Nd1—Ga2ⁱⁱⁱ	3.1497 (6)	Nd1—Nd1ⁱⁱ	3.8954 (8)
Nd1—Ga2^iv	3.1497 (6)	Nd1—Nd1^iv	3.8954 (8)
Nd1—Ga2	3.2386 (12)	Nd1—Nd1ⁱⁱⁱ	3.8954 (8)
Nd1—Ga2^v	3.2556 (8)	Ga2—Ga2^ix	2.6153 (9)
Nd1—Ga2^vi	3.2556 (8)	Ga2—Ga2^x	2.6153 (9)

Ga2ⁱ—Nd1—Ga2ⁱⁱ	150.26 (3)	Ga2^vi—Nd1—Nd1^iv	147.605 (9)
Ga2ⁱ—Nd1—Ga2ⁱⁱⁱ	89.45 (2)	Nd1^vii—Nd1—Nd1^iv	144.622 (11)
Ga2ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	82.99 (2)	Nd1^viii—Nd1—Nd1^iv	103.249 (18)
Ga2ⁱ—Nd1—Ga2^iv	82.99 (2)	Nd1ⁱⁱ—Nd1—Nd1^iv	69.36 (2)
Ga2ⁱⁱ—Nd1—Ga2^iv	89.45 (2)	Ga2ⁱ—Nd1—Nd1ⁱⁱⁱ	101.864 (18)
Ga2ⁱⁱⁱ—Nd1—Ga2^iv	150.26 (3)	Ga2ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	96.581 (19)
Ga2ⁱ—Nd1—Ga2	104.868 (14)	Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱⁱ	53.471 (18)
Ga2ⁱⁱ—Nd1—Ga2	104.868 (13)	Ga2^iv—Nd1—Nd1ⁱⁱⁱ	156.265 (18)
Ga2ⁱⁱⁱ—Nd1—Ga2	104.868 (13)	Ga2—Nd1—Nd1ⁱⁱⁱ	51.397 (13)
Ga2^iv—Nd1—Ga2	104.868 (14)	Ga2^v—Nd1—Nd1ⁱⁱⁱ	147.605 (9)
Ga2ⁱ—Nd1—Ga2^v	48.161 (15)	Ga2^vi—Nd1—Nd1ⁱⁱⁱ	93.99 (2)
Ga2ⁱⁱ—Nd1—Ga2^v	106.928 (18)	Nd1^vii—Nd1—Nd1ⁱⁱⁱ	103.249 (18)
Ga2ⁱⁱⁱ—Nd1—Ga2^v	106.928 (17)	Nd1^viii—Nd1—Nd1ⁱⁱⁱ	144.622 (11)
Ga2^iv—Nd1—Ga2^v	48.161 (15)	Nd1ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	64.782 (19)
Ga2—Nd1—Ga2^v	137.092 (14)	Nd1^iv—Nd1—Nd1ⁱⁱⁱ	102.79 (3)
Ga2ⁱ—Nd1—Ga2^vi	106.928 (17)	Ga2^ix—Ga2—Ga2^x	105.86 (5)
Ga2ⁱⁱ—Nd1—Ga2^vi	48.161 (15)	Ga2^ix—Ga2—Nd1ⁱ	133.103 (17)
Ga2ⁱⁱⁱ—Nd1—Ga2^vi	48.161 (15)	Ga2^x—Ga2—Nd1ⁱ	68.038 (16)
Ga2^iv—Nd1—Ga2^vi	106.928 (17)	Ga2^ix—Ga2—Nd1ⁱⁱ	68.038 (16)
Ga2—Nd1—Ga2^vi	137.092 (14)	Ga2^x—Ga2—Nd1ⁱⁱ	133.103 (16)
Ga2^v—Nd1—Ga2^vi	85.82 (3)	Nd1ⁱ—Ga2—Nd1ⁱⁱ	150.27 (3)
Ga2ⁱ—Nd1—Nd1^vii	54.742 (13)	Ga2^ix—Ga2—Nd1ⁱⁱⁱ	133.103 (16)
Ga2ⁱⁱ—Nd1—Nd1^vii	98.493 (19)	Ga2^x—Ga2—Nd1ⁱⁱⁱ	68.038 (16)
Ga2ⁱⁱⁱ—Nd1—Nd1^vii	54.742 (13)	Nd1ⁱ—Ga2—Nd1ⁱⁱⁱ	89.45 (2)
Ga2^iv—Nd1—Nd1^vii	98.493 (19)	Nd1ⁱⁱ—Ga2—Nd1ⁱⁱⁱ	82.99 (2)
Ga2—Nd1—Nd1^vii	146.831 (12)	Ga2^ix—Ga2—Nd1^iv	68.038 (16)
Ga2^v—Nd1—Nd1^vii	52.185 (14)	Ga2^x—Ga2—Nd1^iv	133.103 (17)
Ga2^vi—Nd1—Nd1^vii	52.185 (14)	Nd1ⁱ—Ga2—Nd1^iv	82.99 (2)
Ga2ⁱ—Nd1—Nd1^viii	98.493 (19)	Nd1ⁱⁱ—Ga2—Nd1^iv	89.45 (2)
Ga2ⁱⁱ—Nd1—Nd1^viii	54.742 (13)	Nd1ⁱⁱⁱ—Ga2—Nd1^iv	150.27 (3)
Ga2ⁱⁱⁱ—Nd1—Nd1^viii	98.493 (19)	Ga2^ix—Ga2—Nd1	127.07 (2)
Ga2^iv—Nd1—Nd1^viii	54.742 (13)	Ga2^x—Ga2—Nd1	127.07 (2)
Ga2—Nd1—Nd1^viii	146.831 (12)	Nd1ⁱ—Ga2—Nd1	75.133 (14)
Ga2^v—Nd1—Nd1^viii	52.185 (14)	Nd1ⁱⁱ—Ga2—Nd1	75.133 (13)
Ga2^vi—Nd1—Nd1^viii	52.185 (14)	Nd1ⁱⁱⁱ—Ga2—Nd1	75.133 (13)
Nd1^vii—Nd1—Nd1^viii	66.34 (2)	Nd1^iv—Ga2—Nd1	75.133 (13)
Ga2ⁱ—Nd1—Nd1ⁱⁱ	156.265 (18)	Ga2^ix—Ga2—Nd1^xi	63.80 (2)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱ	53.471 (18)	Ga2^x—Ga2—Nd1^xi	63.80 (2)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱ	96.581 (19)	Nd1ⁱ—Ga2—Nd1^xi	131.839 (15)
Ga2^iv—Nd1—Nd1ⁱⁱ	101.864 (18)	Nd1ⁱⁱ—Ga2—Nd1^xi	73.072 (18)
Ga2—Nd1—Nd1ⁱⁱ	51.397 (13)	Nd1ⁱⁱⁱ—Ga2—Nd1^xi	73.072 (17)
Ga2^v—Nd1—Nd1ⁱⁱ	147.605 (9)	Nd1^iv—Ga2—Nd1^xi	131.839 (15)
Ga2^vi—Nd1—Nd1ⁱⁱ	93.99 (2)	Nd1—Ga2—Nd1^xi	137.093 (14)
Nd1^vii—Nd1—Nd1ⁱⁱ	144.622 (11)	Ga2^ix—Ga2—Nd1^xii	63.80 (2)
Nd1^viii—Nd1—Nd1ⁱⁱ	103.249 (18)	Ga2^x—Ga2—Nd1^xii	63.80 (2)
Ga2ⁱ—Nd1—Nd1^iv	96.581 (19)	Nd1ⁱ—Ga2—Nd1^xii	73.072 (17)
Ga2ⁱⁱ—Nd1—Nd1^iv	101.864 (18)	Nd1ⁱⁱ—Ga2—Nd1^xii	131.839 (15)
Ga2ⁱⁱⁱ—Nd1—Nd1^iv	156.265 (19)	Nd1ⁱⁱⁱ—Ga2—Nd1^xii	131.839 (15)
Ga2^iv—Nd1—Nd1^iv	53.471 (18)	Nd1^iv—Ga2—Nd1^xii	73.072 (18)
Ga2—Nd1—Nd1^iv	51.397 (13)	Nd1—Ga2—Nd1^xii	137.093 (14)
Ga2^v—Nd1—Nd1^iv	93.99 (2)	Nd1^xi—Ga2—Nd1^xii	85.81 (3)

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

(NdGaH0.9) top

Crystal data top

GaNd	D_x = 6.809 Mg m⁻³
M_r = 213.96	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 1820 reflections
a = 4.1855 (6) Å	θ = 3.4–31.6°
b = 11.9137 (15) Å	µ = 36.99 mm⁻¹
c = 4.1857 (6) Å	T = 296 K
V = 208.72 (5) Å³	Needle
Z = 4	0.03 × 0.01 × 0.01 mm
F(000) = 364

Data collection top

Bruker D8 diffractometer	R_int = 0.015
Absorption correction: multi-scan SADABS	θ_max = 31.6°, θ_min = 3.4°
T_min = 0.641, T_max = 0.698	h = −5→6
1820 measured reflections	k = −17→16
221 independent reflections	l = −6→6
220 reflections with I > 2σ(I)

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: 20
R[F² > 2σ(F²)] = 0.011	w = 1/[σ²(F_o²) + (0.0102P)² + 0.8502P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.026	(Δ/σ)_max < 0.001
S = 1.29	Δρ_max = 1.70 e Å⁻³
221 reflections	Δρ_min = −0.66 e Å⁻³
9 parameters

Special details top

Refinement. Refined as a 2-component perfect inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Nd1	0.000000	0.34572 (2)	0.250000	0.00771 (8)
Ga2	0.000000	0.05794 (4)	0.250000	0.01143 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Nd1	0.00722 (12)	0.00807 (11)	0.00785 (11)	0.000	0.000	0.000
Ga2	0.0167 (3)	0.0112 (2)	0.0064 (2)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Nd1—Ga2ⁱ	3.1744 (4)	Nd1—Nd1ⁱⁱ	3.7365 (4)
Nd1—Ga2ⁱⁱ	3.1744 (4)	Nd1—Nd1^iv	3.7365 (4)
Nd1—Ga2ⁱⁱⁱ	3.1744 (4)	Nd1—Nd1ⁱⁱⁱ	3.7365 (4)
Nd1—Ga2^iv	3.1744 (4)	Nd1—Nd1ⁱ	3.7365 (4)
Nd1—Ga2^v	3.2821 (5)	Ga2—Ga2^vii	2.5072 (6)
Nd1—Ga2^vi	3.2821 (5)	Ga2—Ga2^viii	2.5072 (6)
Nd1—Ga2	3.4285 (7)

Ga2ⁱ—Nd1—Ga2ⁱⁱ	137.61 (2)	Ga2ⁱⁱ—Nd1—Nd1ⁱ	163.577 (13)
Ga2ⁱ—Nd1—Ga2ⁱⁱⁱ	82.487 (13)	Ga2ⁱⁱⁱ—Nd1—Nd1ⁱ	102.747 (11)
Ga2ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	82.491 (12)	Ga2^iv—Nd1—Nd1ⁱ	102.751 (11)
Ga2ⁱ—Nd1—Ga2^iv	82.491 (12)	Ga2^v—Nd1—Nd1ⁱ	96.494 (11)
Ga2ⁱⁱ—Nd1—Ga2^iv	82.487 (12)	Ga2^vi—Nd1—Nd1ⁱ	145.826 (6)
Ga2ⁱⁱⁱ—Nd1—Ga2^iv	137.61 (2)	Ga2—Nd1—Nd1ⁱ	52.382 (7)
Ga2ⁱ—Nd1—Ga2^v	45.663 (11)	Nd1ⁱⁱ—Nd1—Nd1ⁱ	104.764 (14)
Ga2ⁱⁱ—Nd1—Ga2^v	98.154 (10)	Nd1^iv—Nd1—Nd1ⁱ	68.127 (10)
Ga2ⁱⁱⁱ—Nd1—Ga2^v	98.154 (10)	Nd1ⁱⁱⁱ—Nd1—Nd1ⁱ	68.123 (10)
Ga2^iv—Nd1—Ga2^v	45.663 (11)	Ga2^vii—Ga2—Ga2^viii	113.17 (4)
Ga2ⁱ—Nd1—Ga2^vi	98.154 (10)	Ga2^vii—Ga2—Nd1ⁱ	138.540 (8)
Ga2ⁱⁱ—Nd1—Ga2^vi	45.663 (11)	Ga2^viii—Ga2—Nd1ⁱ	69.438 (11)
Ga2ⁱⁱⁱ—Nd1—Ga2^vi	45.663 (11)	Ga2^vii—Ga2—Nd1ⁱⁱ	69.438 (11)
Ga2^iv—Nd1—Ga2^vi	98.154 (10)	Ga2^viii—Ga2—Nd1ⁱⁱ	138.540 (8)
Ga2^v—Nd1—Ga2^vi	79.229 (16)	Nd1ⁱ—Ga2—Nd1ⁱⁱ	137.61 (2)
Ga2ⁱ—Nd1—Ga2	111.195 (10)	Ga2^vii—Ga2—Nd1ⁱⁱⁱ	138.540 (8)
Ga2ⁱⁱ—Nd1—Ga2	111.195 (10)	Ga2^viii—Ga2—Nd1ⁱⁱⁱ	69.438 (11)
Ga2ⁱⁱⁱ—Nd1—Ga2	111.195 (10)	Nd1ⁱ—Ga2—Nd1ⁱⁱⁱ	82.486 (12)
Ga2^iv—Nd1—Ga2	111.195 (10)	Nd1ⁱⁱ—Ga2—Nd1ⁱⁱⁱ	82.491 (13)
Ga2^v—Nd1—Ga2	140.385 (8)	Ga2^vii—Ga2—Nd1^iv	69.438 (10)
Ga2^vi—Nd1—Ga2	140.385 (8)	Ga2^viii—Ga2—Nd1^iv	138.540 (8)
Ga2ⁱ—Nd1—Nd1ⁱⁱ	163.577 (13)	Nd1ⁱ—Ga2—Nd1^iv	82.491 (12)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱ	58.813 (11)	Nd1ⁱⁱ—Ga2—Nd1^iv	82.486 (12)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱ	102.751 (11)	Nd1ⁱⁱⁱ—Ga2—Nd1^iv	137.61 (2)
Ga2^iv—Nd1—Nd1ⁱⁱ	102.747 (11)	Ga2^vii—Ga2—Nd1^ix	64.899 (17)
Ga2^v—Nd1—Nd1ⁱⁱ	145.826 (5)	Ga2^viii—Ga2—Nd1^ix	64.900 (17)
Ga2^vi—Nd1—Nd1ⁱⁱ	96.494 (11)	Nd1ⁱ—Ga2—Nd1^ix	134.338 (10)
Ga2—Nd1—Nd1ⁱⁱ	52.382 (7)	Nd1ⁱⁱ—Ga2—Nd1^ix	81.847 (10)
Ga2ⁱ—Nd1—Nd1^iv	102.751 (11)	Nd1ⁱⁱⁱ—Ga2—Nd1^ix	81.847 (10)
Ga2ⁱⁱ—Nd1—Nd1^iv	102.747 (11)	Nd1^iv—Ga2—Nd1^ix	134.338 (11)
Ga2ⁱⁱⁱ—Nd1—Nd1^iv	163.577 (13)	Ga2^vii—Ga2—Nd1^x	64.899 (17)
Ga2^iv—Nd1—Nd1^iv	58.813 (11)	Ga2^viii—Ga2—Nd1^x	64.899 (17)
Ga2^v—Nd1—Nd1^iv	96.494 (11)	Nd1ⁱ—Ga2—Nd1^x	81.847 (10)
Ga2^vi—Nd1—Nd1^iv	145.826 (6)	Nd1ⁱⁱ—Ga2—Nd1^x	134.338 (11)
Ga2—Nd1—Nd1^iv	52.382 (7)	Nd1ⁱⁱⁱ—Ga2—Nd1^x	134.338 (10)
Nd1ⁱⁱ—Nd1—Nd1^iv	68.123 (10)	Nd1^iv—Ga2—Nd1^x	81.847 (10)
Ga2ⁱ—Nd1—Nd1ⁱⁱⁱ	102.747 (11)	Nd1^ix—Ga2—Nd1^x	79.229 (16)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	102.751 (11)	Ga2^vii—Ga2—Nd1	123.41 (2)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱⁱ	58.813 (11)	Ga2^viii—Ga2—Nd1	123.41 (2)
Ga2^iv—Nd1—Nd1ⁱⁱⁱ	163.577 (13)	Nd1ⁱ—Ga2—Nd1	68.804 (10)
Ga2^v—Nd1—Nd1ⁱⁱⁱ	145.826 (6)	Nd1ⁱⁱ—Ga2—Nd1	68.804 (10)
Ga2^vi—Nd1—Nd1ⁱⁱⁱ	96.494 (11)	Nd1ⁱⁱⁱ—Ga2—Nd1	68.804 (10)
Ga2—Nd1—Nd1ⁱⁱⁱ	52.382 (7)	Nd1^iv—Ga2—Nd1	68.804 (10)
Nd1ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	68.127 (10)	Nd1^ix—Ga2—Nd1	140.385 (8)
Nd1^iv—Nd1—Nd1ⁱⁱⁱ	104.764 (14)	Nd1^x—Ga2—Nd1	140.385 (8)
Ga2ⁱ—Nd1—Nd1ⁱ	58.813 (11)

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

(NdGaH1.1) top

Crystal data top

GaNd	D_x = 6.785 Mg m⁻³
M_r = 213.96	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 1779 reflections
a = 4.1600 (3) Å	θ = 3.4–32.1°
b = 12.0374 (9) Å	µ = 36.86 mm⁻¹
c = 4.1825 (3) Å	T = 296 K
V = 209.44 (3) Å³	Needle
Z = 4	0.03 × 0.01 × 0.01 mm
F(000) = 364

Data collection top

Bruker D8 diffractometer	R_int = 0.029
Absorption correction: multi-scan SADABS	θ_max = 32.1°, θ_min = 3.4°
T_min = 0.641, T_max = 0.698	h = −6→5
1779 measured reflections	k = −17→17
227 independent reflections	l = −6→6
214 reflections with I > 2σ(I)

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: 10
R[F² > 2σ(F²)] = 0.016	w = 1/[σ²(F_o²) + 2.3378P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.032	(Δ/σ)_max < 0.001
S = 1.25	Δρ_max = 1.58 e Å⁻³
227 reflections	Δρ_min = −1.94 e Å⁻³
9 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Nd1	0.000000	0.34524 (3)	0.250000	0.00707 (10)
Ga2	0.000000	0.05698 (7)	0.250000	0.00997 (16)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Nd1	0.00601 (15)	0.00945 (18)	0.00575 (16)	0.000	0.000	0.000
Ga2	0.0140 (3)	0.0104 (4)	0.0055 (3)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Nd1—Ga2ⁱ	3.1757 (4)	Nd1—Nd1ⁱⁱ	3.7359 (5)
Nd1—Ga2ⁱⁱ	3.1757 (4)	Nd1—Nd1ⁱ	3.7359 (5)
Nd1—Ga2ⁱⁱⁱ	3.1757 (4)	Nd1—Nd1ⁱⁱⁱ	3.7359 (5)
Nd1—Ga2^iv	3.1757 (4)	Nd1—Nd1^iv	3.7359 (5)
Nd1—Ga2^v	3.2899 (7)	Ga2—Ga2^vii	2.5011 (9)
Nd1—Ga2^vi	3.2899 (7)	Ga2—Ga2^viii	2.5011 (9)
Nd1—Ga2	3.4698 (9)

Ga2ⁱ—Nd1—Ga2ⁱⁱ	136.49 (3)	Ga2ⁱⁱ—Nd1—Nd1^iv	102.915 (10)
Ga2ⁱ—Nd1—Ga2ⁱⁱⁱ	81.835 (12)	Ga2ⁱⁱⁱ—Nd1—Nd1^iv	163.90 (2)
Ga2ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	82.373 (12)	Ga2^iv—Nd1—Nd1^iv	59.614 (14)
Ga2ⁱ—Nd1—Ga2^iv	82.373 (12)	Ga2^v—Nd1—Nd1^iv	97.094 (10)
Ga2ⁱⁱ—Nd1—Ga2^iv	81.835 (12)	Ga2^vi—Nd1—Nd1^iv	145.844 (6)
Ga2ⁱⁱⁱ—Nd1—Ga2^iv	136.49 (3)	Ga2—Nd1—Nd1^iv	52.140 (9)
Ga2ⁱ—Nd1—Ga2^v	45.472 (15)	Nd1ⁱⁱ—Nd1—Nd1^iv	67.665 (10)
Ga2ⁱⁱ—Nd1—Ga2^v	97.293 (11)	Nd1ⁱ—Nd1—Nd1^iv	68.081 (11)
Ga2ⁱⁱⁱ—Nd1—Ga2^v	97.293 (11)	Nd1ⁱⁱⁱ—Nd1—Nd1^iv	104.281 (19)
Ga2^iv—Nd1—Ga2^v	45.472 (15)	Ga2^vii—Ga2—Ga2^viii	113.47 (6)
Ga2ⁱ—Nd1—Ga2^vi	97.293 (11)	Ga2^vii—Ga2—Nd1ⁱ	138.930 (9)
Ga2ⁱⁱ—Nd1—Ga2^vi	45.472 (15)	Ga2^viii—Ga2—Nd1ⁱ	69.677 (13)
Ga2ⁱⁱⁱ—Nd1—Ga2^vi	45.472 (15)	Ga2^vii—Ga2—Nd1ⁱⁱ	69.677 (12)
Ga2^iv—Nd1—Ga2^vi	97.293 (11)	Ga2^viii—Ga2—Nd1ⁱⁱ	138.930 (9)
Ga2^v—Nd1—Ga2^vi	78.432 (19)	Nd1ⁱ—Ga2—Nd1ⁱⁱ	136.49 (3)
Ga2ⁱ—Nd1—Ga2	111.755 (16)	Ga2^vii—Ga2—Nd1ⁱⁱⁱ	138.930 (9)
Ga2ⁱⁱ—Nd1—Ga2	111.755 (16)	Ga2^viii—Ga2—Nd1ⁱⁱⁱ	69.677 (12)
Ga2ⁱⁱⁱ—Nd1—Ga2	111.755 (16)	Nd1ⁱ—Ga2—Nd1ⁱⁱⁱ	81.836 (12)
Ga2^iv—Nd1—Ga2	111.755 (16)	Nd1ⁱⁱ—Ga2—Nd1ⁱⁱⁱ	82.374 (12)
Ga2^v—Nd1—Ga2	140.784 (10)	Ga2^vii—Ga2—Nd1^iv	69.677 (13)
Ga2^vi—Nd1—Ga2	140.784 (10)	Ga2^viii—Ga2—Nd1^iv	138.930 (9)
Ga2ⁱ—Nd1—Nd1ⁱⁱ	163.90 (2)	Nd1ⁱ—Ga2—Nd1^iv	82.374 (12)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱ	59.614 (14)	Nd1ⁱⁱ—Ga2—Nd1^iv	81.836 (12)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱ	103.381 (10)	Nd1ⁱⁱⁱ—Ga2—Nd1^iv	136.49 (3)
Ga2^iv—Nd1—Nd1ⁱⁱ	102.915 (10)	Ga2^vii—Ga2—Nd1^ix	64.85 (3)
Ga2^v—Nd1—Nd1ⁱⁱ	145.844 (6)	Ga2^viii—Ga2—Nd1^ix	64.85 (3)
Ga2^vi—Nd1—Nd1ⁱⁱ	97.094 (10)	Nd1ⁱ—Ga2—Nd1^ix	134.527 (15)
Ga2—Nd1—Nd1ⁱⁱ	52.140 (9)	Nd1ⁱⁱ—Ga2—Nd1^ix	82.706 (11)
Ga2ⁱ—Nd1—Nd1ⁱ	59.614 (14)	Nd1ⁱⁱⁱ—Ga2—Nd1^ix	82.706 (11)
Ga2ⁱⁱ—Nd1—Nd1ⁱ	163.90 (2)	Nd1^iv—Ga2—Nd1^ix	134.527 (15)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱ	102.915 (10)	Ga2^vii—Ga2—Nd1^x	64.85 (3)
Ga2^iv—Nd1—Nd1ⁱ	103.381 (10)	Ga2^viii—Ga2—Nd1^x	64.85 (3)
Ga2^v—Nd1—Nd1ⁱ	97.093 (10)	Nd1ⁱ—Ga2—Nd1^x	82.706 (11)
Ga2^vi—Nd1—Nd1ⁱ	145.844 (6)	Nd1ⁱⁱ—Ga2—Nd1^x	134.527 (15)
Ga2—Nd1—Nd1ⁱ	52.140 (10)	Nd1ⁱⁱⁱ—Ga2—Nd1^x	134.527 (15)
Nd1ⁱⁱ—Nd1—Nd1ⁱ	104.281 (19)	Nd1^iv—Ga2—Nd1^x	82.706 (11)
Ga2ⁱ—Nd1—Nd1ⁱⁱⁱ	102.915 (10)	Nd1^ix—Ga2—Nd1^x	78.432 (19)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	103.381 (10)	Ga2^vii—Ga2—Nd1	123.27 (3)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱⁱ	59.614 (14)	Ga2^viii—Ga2—Nd1	123.27 (3)
Ga2^iv—Nd1—Nd1ⁱⁱⁱ	163.90 (2)	Nd1ⁱ—Ga2—Nd1	68.246 (16)
Ga2^v—Nd1—Nd1ⁱⁱⁱ	145.844 (6)	Nd1ⁱⁱ—Ga2—Nd1	68.246 (16)
Ga2^vi—Nd1—Nd1ⁱⁱⁱ	97.094 (10)	Nd1ⁱⁱⁱ—Ga2—Nd1	68.246 (16)
Ga2—Nd1—Nd1ⁱⁱⁱ	52.140 (9)	Nd1^iv—Ga2—Nd1	68.246 (16)
Nd1ⁱⁱ—Nd1—Nd1ⁱⁱⁱ	68.081 (11)	Nd1^ix—Ga2—Nd1	140.784 (10)
Nd1ⁱ—Nd1—Nd1ⁱⁱⁱ	67.665 (11)	Nd1^x—Ga2—Nd1	140.784 (10)
Ga2ⁱ—Nd1—Nd1^iv	103.381 (10)

(NdGaH1.2) top

Crystal data top

GaNd	D_x = 6.755 Mg m⁻³
M_r = 213.96	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 7143 reflections
a = 12.3380 (6) Å	θ = 2.3–32.5°
b = 12.2710 (9) Å	µ = 36.69 mm⁻¹
c = 4.1691 (2) Å	T = 296 K
V = 631.20 (6) Å³	Needle
Z = 12	0.03 × 0.01 × 0.01 mm
F(000) = 1092

Data collection top

Bruker D8 diffractometer	R_int = 0.057
Absorption correction: multi-scan SADABS	θ_max = 32.5°, θ_min = 2.3°
T_min = 0.641, T_max = 0.698	h = −18→18
7143 measured reflections	k = −18→14
635 independent reflections	l = −6→5
511 reflections with I > 2σ(I)

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: 12
R[F² > 2σ(F²)] = 0.028	w = 1/[σ²(F_o²) + (0.0218P)² + 6.0517P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.057	(Δ/σ)_max < 0.001
S = 1.06	Δρ_max = 2.38 e Å⁻³
635 reflections	Δρ_min = −2.08 e Å⁻³
22 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Nd1	0.32999 (3)	0.35426 (3)	0.250000	0.00728 (14)
Nd2	0.000000	0.33415 (5)	0.250000	0.00708 (17)
Ga1	0.34928 (7)	0.05844 (7)	0.250000	0.0096 (2)
Ga2	0.000000	0.05939 (10)	0.250000	0.0083 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Nd1	0.00633 (19)	0.0100 (2)	0.0055 (2)	−0.00041 (14)	0.000	0.000
Nd2	0.0055 (2)	0.0105 (3)	0.0052 (3)	0.000	0.000	0.000
Ga1	0.0104 (4)	0.0128 (4)	0.0057 (4)	−0.0012 (3)	0.000	0.000
Ga2	0.0081 (5)	0.0107 (6)	0.0060 (6)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Nd1—Ga2ⁱ	3.1413 (5)	Nd2—Ga1ⁱ	3.0888 (7)
Nd1—Ga2ⁱⁱ	3.1413 (5)	Nd2—Ga1^v	3.0888 (7)
Nd1—Ga1ⁱⁱ	3.2226 (7)	Nd2—Ga1^vi	3.0888 (7)
Nd1—Ga1ⁱ	3.2226 (7)	Nd2—Ga1ⁱⁱ	3.0888 (7)
Nd1—Ga2ⁱⁱⁱ	3.2765 (10)	Nd2—Ga1^iv	3.3216 (10)
Nd1—Ga1^iv	3.3421 (9)	Nd2—Ga1^vii	3.3216 (10)
Nd1—Nd2ⁱ	3.7537 (5)	Nd2—Ga2	3.3716 (14)
Nd1—Nd2ⁱⁱ	3.7537 (5)	Ga1—Ga1^viii	2.5303 (10)
Nd1—Nd1ⁱⁱ	3.8457 (7)	Ga1—Ga1^ix	2.5303 (10)
Nd1—Nd1ⁱ	3.8456 (7)	Ga2—Ga2^x	2.5436 (14)
Nd1—Nd2	4.0789 (4)	Ga2—Ga2^xi	2.5436 (14)

Ga2ⁱ—Nd1—Ga2ⁱⁱ	83.148 (17)	Ga1^vi—Nd2—Nd1^vi	63.361 (18)
Ga2ⁱ—Nd1—Ga1ⁱⁱ	140.84 (3)	Ga1ⁱⁱ—Nd2—Nd1^vi	166.91 (2)
Ga2ⁱⁱ—Nd1—Ga1ⁱⁱ	85.235 (15)	Ga1^iv—Nd2—Nd1^vi	145.405 (8)
Ga2ⁱ—Nd1—Ga1ⁱ	85.235 (15)	Ga1^vii—Nd2—Nd1^vi	101.392 (14)
Ga2ⁱⁱ—Nd1—Ga1ⁱ	140.84 (3)	Ga2—Nd2—Nd1^vi	51.981 (10)
Ga1ⁱⁱ—Nd1—Ga1ⁱ	80.61 (2)	Nd1^v—Nd2—Nd1^vi	67.467 (11)
Ga2ⁱ—Nd1—Ga2ⁱⁱⁱ	46.64 (2)	Nd1ⁱⁱ—Nd2—Nd1^vi	103.96 (2)
Ga2ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	46.64 (2)	Ga1ⁱ—Nd2—Nd1ⁱ	63.361 (18)
Ga1ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	100.60 (2)	Ga1^v—Nd2—Nd1ⁱ	166.91 (2)
Ga1ⁱ—Nd1—Ga2ⁱⁱⁱ	100.60 (2)	Ga1^vi—Nd2—Nd1ⁱ	102.971 (12)
Ga2ⁱ—Nd1—Ga1^iv	100.90 (2)	Ga1ⁱⁱ—Nd2—Nd1ⁱ	107.529 (16)
Ga2ⁱⁱ—Nd1—Ga1^iv	100.90 (2)	Ga1^iv—Nd2—Nd1ⁱ	101.392 (14)
Ga1ⁱⁱ—Nd1—Ga1^iv	45.296 (19)	Ga1^vii—Nd2—Nd1ⁱ	145.405 (9)
Ga1ⁱ—Nd1—Ga1^iv	45.296 (19)	Ga2—Nd2—Nd1ⁱ	51.981 (10)
Ga2ⁱⁱⁱ—Nd1—Ga1^iv	81.24 (2)	Nd1^v—Nd2—Nd1ⁱ	103.96 (2)
Ga2ⁱ—Nd1—Nd2ⁱ	57.73 (2)	Nd1ⁱⁱ—Nd2—Nd1ⁱ	67.467 (11)
Ga2ⁱⁱ—Nd1—Nd2ⁱ	101.721 (17)	Nd1^vi—Nd2—Nd1ⁱ	67.944 (14)
Ga1ⁱⁱ—Nd1—Nd2ⁱ	161.35 (2)	Ga1ⁱ—Nd2—Nd1	51.189 (13)
Ga1ⁱ—Nd1—Nd2ⁱ	103.242 (12)	Ga1^v—Nd2—Nd1	125.108 (17)
Ga2ⁱⁱⁱ—Nd1—Nd2ⁱ	96.629 (16)	Ga1^vi—Nd2—Nd1	125.108 (17)
Ga1^iv—Nd1—Nd2ⁱ	146.259 (6)	Ga1ⁱⁱ—Nd2—Nd1	51.189 (13)
Ga2ⁱ—Nd1—Nd2ⁱⁱ	101.721 (17)	Ga1^iv—Nd2—Nd1	52.487 (16)
Ga2ⁱⁱ—Nd1—Nd2ⁱⁱ	57.73 (2)	Ga1^vii—Nd2—Nd1	120.58 (2)
Ga1ⁱⁱ—Nd1—Nd2ⁱⁱ	103.242 (12)	Ga2—Nd2—Nd1	93.469 (10)
Ga1ⁱ—Nd1—Nd2ⁱⁱ	161.35 (2)	Nd1^v—Nd2—Nd1	126.515 (11)
Ga2ⁱⁱⁱ—Nd1—Nd2ⁱⁱ	96.629 (16)	Nd1ⁱⁱ—Nd2—Nd1	58.634 (9)
Ga1^iv—Nd1—Nd2ⁱⁱ	146.259 (6)	Nd1^vi—Nd2—Nd1	126.515 (11)
Nd2ⁱ—Nd1—Nd2ⁱⁱ	67.467 (11)	Nd1ⁱ—Nd2—Nd1	58.634 (9)
Ga2ⁱ—Nd1—Nd1ⁱⁱ	157.95 (3)	Ga1^viii—Ga1—Ga1^ix	110.94 (7)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱ	101.975 (15)	Ga1^viii—Ga1—Nd2ⁱ	142.925 (16)
Ga1ⁱⁱ—Nd1—Nd1ⁱⁱ	61.201 (17)	Ga1^ix—Ga1—Nd2ⁱ	71.692 (16)
Ga1ⁱ—Nd1—Nd1ⁱⁱ	102.68 (2)	Ga1^viii—Ga1—Nd2ⁱⁱ	71.692 (16)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱ	147.114 (7)	Ga1^ix—Ga1—Nd2ⁱⁱ	142.925 (16)
Ga1^iv—Nd1—Nd1ⁱⁱ	99.155 (18)	Nd2ⁱ—Ga1—Nd2ⁱⁱ	84.89 (2)
Nd2ⁱ—Nd1—Nd1ⁱⁱ	100.255 (17)	Ga1^viii—Ga1—Nd1ⁱⁱ	69.851 (13)
Nd2ⁱⁱ—Nd1—Nd1ⁱⁱ	64.912 (11)	Ga1^ix—Ga1—Nd1ⁱⁱ	136.164 (17)
Ga2ⁱ—Nd1—Nd1ⁱ	101.975 (15)	Nd2ⁱ—Ga1—Nd1ⁱⁱ	135.07 (3)
Ga2ⁱⁱ—Nd1—Nd1ⁱ	157.95 (3)	Nd2ⁱⁱ—Ga1—Nd1ⁱⁱ	80.494 (13)
Ga1ⁱⁱ—Nd1—Nd1ⁱ	102.68 (2)	Ga1^viii—Ga1—Nd1ⁱ	136.164 (17)
Ga1ⁱ—Nd1—Nd1ⁱ	61.201 (17)	Ga1^ix—Ga1—Nd1ⁱ	69.851 (13)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱ	147.114 (7)	Nd2ⁱ—Ga1—Nd1ⁱ	80.494 (13)
Ga1^iv—Nd1—Nd1ⁱ	99.155 (18)	Nd2ⁱⁱ—Ga1—Nd1ⁱ	135.07 (3)
Nd2ⁱ—Nd1—Nd1ⁱ	64.912 (10)	Nd1ⁱⁱ—Ga1—Nd1ⁱ	80.61 (2)
Nd2ⁱⁱ—Nd1—Nd1ⁱ	100.255 (17)	Ga1^viii—Ga1—Nd2^xii	61.99 (3)
Nd1ⁱⁱ—Nd1—Nd1ⁱ	65.647 (13)	Ga1^ix—Ga1—Nd2^xii	61.99 (3)
Ga2ⁱ—Nd1—Nd2	133.387 (9)	Nd2ⁱ—Ga1—Nd2^xii	90.95 (2)
Ga2ⁱⁱ—Nd1—Nd2	133.387 (9)	Nd2ⁱⁱ—Ga1—Nd2^xii	90.95 (2)
Ga1ⁱⁱ—Nd1—Nd2	48.319 (14)	Nd1ⁱⁱ—Ga1—Nd2^xii	131.276 (19)
Ga1ⁱ—Nd1—Nd2	48.319 (14)	Nd1ⁱ—Ga1—Nd2^xii	131.276 (19)
Ga2ⁱⁱⁱ—Nd1—Nd2	133.27 (2)	Ga1^viii—Ga1—Nd1^xiii	64.85 (3)
Ga1^iv—Nd1—Nd2	52.031 (18)	Ga1^ix—Ga1—Nd1^xiii	64.85 (3)
Nd2ⁱ—Nd1—Nd2	121.366 (9)	Nd2ⁱ—Ga1—Nd1^xiii	135.917 (16)
Nd2ⁱⁱ—Nd1—Nd2	121.366 (9)	Nd2ⁱⁱ—Ga1—Nd1^xiii	135.917 (16)
Nd1ⁱⁱ—Nd1—Nd2	56.455 (11)	Nd1ⁱⁱ—Ga1—Nd1^xiii	78.17 (2)
Nd1ⁱ—Nd1—Nd2	56.455 (11)	Nd1ⁱ—Ga1—Nd1^xiii	78.17 (2)
Ga1ⁱ—Nd2—Ga1^v	129.48 (4)	Nd2^xii—Ga1—Nd1^xiii	75.48 (2)
Ga1ⁱ—Nd2—Ga1^vi	74.03 (3)	Ga2^x—Ga2—Ga2^xi	110.08 (9)
Ga1^v—Nd2—Ga1^vi	84.89 (2)	Ga2^x—Ga2—Nd1ⁱ	137.487 (19)
Ga1ⁱ—Nd2—Ga1ⁱⁱ	84.89 (2)	Ga2^xi—Ga2—Nd1ⁱ	69.478 (16)
Ga1^v—Nd2—Ga1ⁱⁱ	74.03 (3)	Ga2^x—Ga2—Nd1^v	69.478 (16)
Ga1^vi—Nd2—Ga1ⁱⁱ	129.48 (4)	Ga2^xi—Ga2—Nd1^v	137.487 (19)
Ga1ⁱ—Nd2—Ga1^iv	46.321 (18)	Nd1ⁱ—Ga2—Nd1^v	140.57 (5)
Ga1^v—Nd2—Ga1^iv	89.05 (2)	Ga2^x—Ga2—Nd1^vi	137.487 (19)
Ga1^vi—Nd2—Ga1^iv	89.05 (2)	Ga2^xi—Ga2—Nd1^vi	69.478 (16)
Ga1ⁱⁱ—Nd2—Ga1^iv	46.321 (18)	Nd1ⁱ—Ga2—Nd1^vi	83.784 (18)
Ga1ⁱ—Nd2—Ga1^vii	89.05 (2)	Nd1^v—Ga2—Nd1^vi	83.150 (17)
Ga1^v—Nd2—Ga1^vii	46.321 (18)	Ga2^x—Ga2—Nd1ⁱⁱ	69.478 (16)
Ga1^vi—Nd2—Ga1^vii	46.321 (18)	Ga2^xi—Ga2—Nd1ⁱⁱ	137.487 (19)
Ga1ⁱⁱ—Nd2—Ga1^vii	89.05 (2)	Nd1ⁱ—Ga2—Nd1ⁱⁱ	83.150 (17)
Ga1^iv—Nd2—Ga1^vii	68.09 (3)	Nd1^v—Ga2—Nd1ⁱⁱ	83.784 (18)
Ga1ⁱ—Nd2—Ga2	115.26 (2)	Nd1^vi—Ga2—Nd1ⁱⁱ	140.57 (5)
Ga1^v—Nd2—Ga2	115.26 (2)	Ga2^x—Ga2—Nd1^xiv	63.88 (4)
Ga1^vi—Nd2—Ga2	115.26 (2)	Ga2^xi—Ga2—Nd1^xiv	63.88 (4)
Ga1ⁱⁱ—Nd2—Ga2	115.26 (2)	Nd1ⁱ—Ga2—Nd1^xiv	133.36 (2)
Ga1^iv—Nd2—Ga2	145.955 (16)	Nd1^v—Ga2—Nd1^xiv	80.309 (16)
Ga1^vii—Nd2—Ga2	145.955 (16)	Nd1^vi—Ga2—Nd1^xiv	80.309 (16)
Ga1ⁱ—Nd2—Nd1^v	166.91 (2)	Nd1ⁱⁱ—Ga2—Nd1^xiv	133.36 (2)
Ga1^v—Nd2—Nd1^v	63.361 (18)	Ga2^x—Ga2—Nd1^xiii	63.88 (4)
Ga1^vi—Nd2—Nd1^v	107.529 (16)	Ga2^xi—Ga2—Nd1^xiii	63.88 (4)
Ga1ⁱⁱ—Nd2—Nd1^v	102.971 (12)	Nd1ⁱ—Ga2—Nd1^xiii	80.309 (16)
Ga1^iv—Nd2—Nd1^v	145.405 (8)	Nd1^v—Ga2—Nd1^xiii	133.36 (2)
Ga1^vii—Nd2—Nd1^v	101.392 (14)	Nd1^vi—Ga2—Nd1^xiii	133.36 (2)
Ga2—Nd2—Nd1^v	51.981 (10)	Nd1ⁱⁱ—Ga2—Nd1^xiii	80.309 (16)
Ga1ⁱ—Nd2—Nd1ⁱⁱ	107.529 (16)	Nd1^xiv—Ga2—Nd1^xiii	79.61 (3)
Ga1^v—Nd2—Nd1ⁱⁱ	102.971 (12)	Ga2^x—Ga2—Nd2	124.96 (5)
Ga1^vi—Nd2—Nd1ⁱⁱ	166.91 (2)	Ga2^xi—Ga2—Nd2	124.96 (5)
Ga1ⁱⁱ—Nd2—Nd1ⁱⁱ	63.361 (18)	Nd1ⁱ—Ga2—Nd2	70.29 (2)
Ga1^iv—Nd2—Nd1ⁱⁱ	101.392 (14)	Nd1^v—Ga2—Nd2	70.29 (2)
Ga1^vii—Nd2—Nd1ⁱⁱ	145.405 (8)	Nd1^vi—Ga2—Nd2	70.29 (2)
Ga2—Nd2—Nd1ⁱⁱ	51.981 (10)	Nd1ⁱⁱ—Ga2—Nd2	70.29 (2)
Nd1^v—Nd2—Nd1ⁱⁱ	67.944 (14)	Nd1^xiv—Ga2—Nd2	140.195 (15)
Ga1ⁱ—Nd2—Nd1^vi	102.971 (12)	Nd1^xiii—Ga2—Nd2	140.195 (15)
Ga1^v—Nd2—Nd1^vi	107.529 (16)

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

(NdGaH1.6) top

Crystal data top

Ga₃Nd₃	D_x = 6.747 Mg m⁻³
M_r = 641.88	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 7329 reflections
a = 12.332 (2) Å	θ = 2.3–39.4°
b = 12.264 (2) Å	µ = 36.65 mm⁻¹
c = 4.1782 (7) Å	T = 296 K
V = 631.93 (19) Å³	Needle
Z = 4	0.03 × 0.01 × 0.01 mm
F(000) = 1092

Data collection top

Bruker D8 diffractometer	R_int = 0.031
Absorption correction: multi-scan SADABS	θ_max = 39.4°, θ_min = 2.3°
T_min = 0.641, T_max = 0.698	h = −21→21
7329 measured reflections	k = −21→21
1070 independent reflections	l = −7→7
919 reflections with I > 2σ(I)

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: 12
R[F² > 2σ(F²)] = 0.030	w = 1/[σ²(F_o²) + (0.0253P)² + 17.8283P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.068	(Δ/σ)_max = 0.001
S = 1.08	Δρ_max = 4.22 e Å⁻³
1070 reflections	Δρ_min = −3.41 e Å⁻³
21 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Nd1	0.33074 (2)	0.35288 (2)	0.250000	0.00599 (7)
Nd2	0.000000	0.33632 (3)	0.250000	0.00632 (8)
Ga2	0.000000	0.05919 (7)	0.250000	0.00782 (15)
Ga1	0.34675 (6)	0.05837 (6)	0.250000	0.00990 (13)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Nd1	0.00493 (11)	0.00808 (12)	0.00497 (12)	−0.00097 (8)	0.000	0.000
Nd2	0.00459 (15)	0.00972 (17)	0.00465 (17)	0.000	0.000	0.000
Ga2	0.0102 (4)	0.0076 (3)	0.0056 (4)	0.000	0.000	0.000
Ga1	0.0150 (3)	0.0092 (3)	0.0055 (3)	−0.0014 (2)	0.000	0.000

Geometric parameters (Å, º) top

Nd1—Ga2ⁱ	3.1440 (5)	Nd2—Ga1ⁱ	3.0991 (6)
Nd1—Ga2ⁱⁱ	3.1440 (5)	Nd2—Ga1^v	3.0991 (6)
Nd1—Ga1ⁱⁱ	3.2156 (7)	Nd2—Ga1^vi	3.0991 (6)
Nd1—Ga1ⁱ	3.2156 (7)	Nd2—Ga1ⁱⁱ	3.0991 (6)
Nd1—Ga2ⁱⁱⁱ	3.2801 (9)	Nd2—Ga1^iv	3.3148 (9)
Nd1—Ga1^iv	3.3380 (9)	Nd2—Ga1^vii	3.3148 (9)
Nd1—Nd2ⁱⁱ	3.7557 (5)	Nd2—Ga2	3.3988 (12)
Nd1—Nd2ⁱ	3.7557 (5)	Ga2—Ga2^viii	2.5440 (11)
Nd1—Nd1ⁱⁱ	3.8338 (6)	Ga2—Ga2^ix	2.5440 (11)
Nd1—Nd1ⁱ	3.8338 (6)	Ga1—Ga1^x	2.5326 (9)
Nd1—Nd2	4.0838 (7)	Ga1—Ga1^xi	2.5326 (9)

Ga2ⁱ—Nd1—Ga2ⁱⁱ	83.285 (17)	Ga1^vi—Nd2—Nd1^vi	62.843 (17)
Ga2ⁱ—Nd1—Ga1ⁱⁱ	140.13 (2)	Ga1ⁱⁱ—Nd2—Nd1^vi	166.257 (18)
Ga2ⁱⁱ—Nd1—Ga1ⁱⁱ	84.499 (17)	Ga1^iv—Nd2—Nd1^vi	145.533 (8)
Ga2ⁱ—Nd1—Ga1ⁱ	84.499 (17)	Ga1^vii—Nd2—Nd1^vi	100.993 (16)
Ga2ⁱⁱ—Nd1—Ga1ⁱ	140.13 (2)	Ga2—Nd2—Nd1^vi	51.843 (9)
Ga1ⁱⁱ—Nd1—Ga1ⁱ	81.04 (2)	Nd1^v—Nd2—Nd1^vi	67.591 (14)
Ga2ⁱ—Nd1—Ga2ⁱⁱⁱ	46.599 (18)	Nd1ⁱⁱ—Nd2—Nd1^vi	103.685 (18)
Ga2ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	46.599 (18)	Ga1ⁱ—Nd2—Nd1ⁱ	62.843 (17)
Ga1ⁱⁱ—Nd1—Ga2ⁱⁱⁱ	99.909 (19)	Ga1^v—Nd2—Nd1ⁱ	166.257 (18)
Ga1ⁱ—Nd1—Ga2ⁱⁱⁱ	99.909 (19)	Ga1^vi—Nd2—Nd1ⁱ	102.794 (15)
Ga2ⁱ—Nd1—Ga1^iv	100.16 (2)	Ga1ⁱⁱ—Nd2—Nd1ⁱ	107.067 (17)
Ga2ⁱⁱ—Nd1—Ga1^iv	100.16 (2)	Ga1^iv—Nd2—Nd1ⁱ	100.993 (16)
Ga1ⁱⁱ—Nd1—Ga1^iv	45.420 (16)	Ga1^vii—Nd2—Nd1ⁱ	145.533 (8)
Ga1ⁱ—Nd1—Ga1^iv	45.420 (16)	Ga2—Nd2—Nd1ⁱ	51.843 (9)
Ga2ⁱⁱⁱ—Nd1—Ga1^iv	80.50 (2)	Nd1^v—Nd2—Nd1ⁱ	103.685 (18)
Ga2ⁱ—Nd1—Nd2ⁱⁱ	102.270 (16)	Nd1ⁱⁱ—Nd2—Nd1ⁱ	67.591 (13)
Ga2ⁱⁱ—Nd1—Nd2ⁱⁱ	58.22 (2)	Nd1^vi—Nd2—Nd1ⁱ	67.530 (14)
Ga1ⁱⁱ—Nd1—Nd2ⁱⁱ	103.065 (15)	Ga1ⁱ—Nd2—Nd1^xii	126.041 (15)
Ga1ⁱ—Nd1—Nd2ⁱⁱ	161.590 (17)	Ga1^v—Nd2—Nd1^xii	50.963 (13)
Ga2ⁱⁱⁱ—Nd1—Nd2ⁱⁱ	97.058 (16)	Ga1^vi—Nd2—Nd1^xii	50.963 (13)
Ga1^iv—Nd1—Nd2ⁱⁱ	146.191 (7)	Ga1ⁱⁱ—Nd2—Nd1^xii	126.041 (15)
Ga2ⁱ—Nd1—Nd2ⁱ	58.22 (2)	Ga1^iv—Nd2—Nd1^xii	121.910 (18)
Ga2ⁱⁱ—Nd1—Nd2ⁱ	102.270 (16)	Ga1^vii—Nd2—Nd1^xii	52.388 (14)
Ga1ⁱⁱ—Nd1—Nd2ⁱ	161.590 (17)	Ga2—Nd2—Nd1^xii	92.851 (7)
Ga1ⁱ—Nd1—Nd2ⁱ	103.065 (15)	Nd1^v—Nd2—Nd1^xii	58.374 (9)
Ga2ⁱⁱⁱ—Nd1—Nd2ⁱ	97.058 (16)	Nd1ⁱⁱ—Nd2—Nd1^xii	125.861 (9)
Ga1^iv—Nd1—Nd2ⁱ	146.191 (7)	Nd1^vi—Nd2—Nd1^xii	58.374 (9)
Nd2ⁱⁱ—Nd1—Nd2ⁱ	67.593 (13)	Nd1ⁱ—Nd2—Nd1^xii	125.861 (9)
Ga2ⁱ—Nd1—Nd1ⁱⁱ	158.86 (2)	Ga2^viii—Ga2—Ga2^ix	110.41 (7)
Ga2ⁱⁱ—Nd1—Nd1ⁱⁱ	102.037 (15)	Ga2^viii—Ga2—Nd1ⁱ	137.850 (15)
Ga1ⁱⁱ—Nd1—Nd1ⁱⁱ	61.001 (17)	Ga2^ix—Ga2—Nd1ⁱ	69.518 (16)
Ga1ⁱ—Nd1—Nd1ⁱⁱ	102.900 (19)	Ga2^viii—Ga2—Nd1^v	69.518 (16)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱⁱ	146.960 (8)	Ga2^ix—Ga2—Nd1^v	137.850 (15)
Ga1^iv—Nd1—Nd1ⁱⁱ	98.996 (19)	Nd1ⁱ—Ga2—Nd1^v	139.88 (3)
Nd2ⁱⁱ—Nd1—Nd1ⁱⁱ	65.097 (13)	Ga2^viii—Ga2—Nd1^vi	137.850 (15)
Nd2ⁱ—Nd1—Nd1ⁱⁱ	100.669 (17)	Ga2^ix—Ga2—Nd1^vi	69.518 (16)
Ga2ⁱ—Nd1—Nd1ⁱ	102.037 (15)	Nd1ⁱ—Ga2—Nd1^vi	83.203 (18)
Ga2ⁱⁱ—Nd1—Nd1ⁱ	158.86 (2)	Nd1^v—Ga2—Nd1^vi	83.284 (17)
Ga1ⁱⁱ—Nd1—Nd1ⁱ	102.900 (19)	Ga2^viii—Ga2—Nd1ⁱⁱ	69.518 (15)
Ga1ⁱ—Nd1—Nd1ⁱ	61.001 (17)	Ga2^ix—Ga2—Nd1ⁱⁱ	137.850 (15)
Ga2ⁱⁱⁱ—Nd1—Nd1ⁱ	146.960 (8)	Nd1ⁱ—Ga2—Nd1ⁱⁱ	83.284 (17)
Ga1^iv—Nd1—Nd1ⁱ	98.996 (19)	Nd1^v—Ga2—Nd1ⁱⁱ	83.203 (18)
Nd2ⁱⁱ—Nd1—Nd1ⁱ	100.669 (17)	Nd1^vi—Ga2—Nd1ⁱⁱ	139.88 (3)
Nd2ⁱ—Nd1—Nd1ⁱ	65.097 (13)	Ga2^viii—Ga2—Nd1^xiii	63.88 (3)
Nd1ⁱⁱ—Nd1—Nd1ⁱ	66.039 (14)	Ga2^ix—Ga2—Nd1^xiii	63.88 (3)
Ga2ⁱ—Nd1—Nd2	132.857 (9)	Nd1ⁱ—Ga2—Nd1^xiii	133.401 (18)
Ga2ⁱⁱ—Nd1—Nd2	132.857 (9)	Nd1^v—Ga2—Nd1^xiii	80.912 (15)
Ga1ⁱⁱ—Nd1—Nd2	48.469 (13)	Nd1^vi—Ga2—Nd1^xiii	80.912 (15)
Ga1ⁱ—Nd1—Nd2	48.469 (13)	Nd1ⁱⁱ—Ga2—Nd1^xiii	133.401 (18)
Ga2ⁱⁱⁱ—Nd1—Nd2	132.373 (15)	Ga2^viii—Ga2—Nd1^xiv	63.88 (3)
Ga1^iv—Nd1—Nd2	51.875 (16)	Ga2^ix—Ga2—Nd1^xiv	63.88 (3)
Nd2ⁱⁱ—Nd1—Nd2	121.626 (8)	Nd1ⁱ—Ga2—Nd1^xiv	80.912 (15)
Nd2ⁱ—Nd1—Nd2	121.626 (9)	Nd1^v—Ga2—Nd1^xiv	133.401 (18)
Nd1ⁱⁱ—Nd1—Nd2	56.529 (10)	Nd1^vi—Ga2—Nd1^xiv	133.401 (18)
Nd1ⁱ—Nd1—Nd2	56.529 (10)	Nd1ⁱⁱ—Ga2—Nd1^xiv	80.912 (15)
Ga1ⁱ—Nd2—Ga1^v	130.74 (3)	Nd1^xiii—Ga2—Nd1^xiv	79.05 (3)
Ga1ⁱ—Nd2—Ga1^vi	75.16 (3)	Ga2^viii—Ga2—Nd2	124.80 (3)
Ga1^v—Nd2—Ga1^vi	84.77 (2)	Ga2^ix—Ga2—Nd2	124.80 (3)
Ga1ⁱ—Nd2—Ga1ⁱⁱ	84.77 (2)	Nd1ⁱ—Ga2—Nd2	69.941 (17)
Ga1^v—Nd2—Ga1ⁱⁱ	75.16 (3)	Nd1^v—Ga2—Nd2	69.941 (17)
Ga1^vi—Nd2—Ga1ⁱⁱ	130.74 (3)	Nd1^vi—Ga2—Nd2	69.941 (17)
Ga1ⁱ—Nd2—Ga1^iv	46.365 (15)	Nd1ⁱⁱ—Ga2—Nd2	69.941 (17)
Ga1^v—Nd2—Ga1^iv	90.31 (2)	Nd1^xiii—Ga2—Nd2	140.477 (13)
Ga1^vi—Nd2—Ga1^iv	90.31 (2)	Nd1^xiv—Ga2—Nd2	140.477 (13)
Ga1ⁱⁱ—Nd2—Ga1^iv	46.365 (15)	Ga1^x—Ga1—Ga1^xi	111.15 (5)
Ga1ⁱ—Nd2—Ga1^vii	90.31 (2)	Ga1^x—Ga1—Nd2ⁱ	142.340 (14)
Ga1^v—Nd2—Ga1^vii	46.365 (15)	Ga1^xi—Ga1—Nd2ⁱ	71.310 (16)
Ga1^vi—Nd2—Ga1^vii	46.365 (15)	Ga1^x—Ga1—Nd2ⁱⁱ	71.310 (16)
Ga1ⁱⁱ—Nd2—Ga1^vii	90.31 (2)	Ga1^xi—Ga1—Nd2ⁱⁱ	142.340 (14)
Ga1^iv—Nd2—Ga1^vii	69.52 (3)	Nd2ⁱ—Ga1—Nd2ⁱⁱ	84.77 (2)
Ga1ⁱ—Nd2—Ga2	114.629 (15)	Ga1^x—Ga1—Nd1ⁱⁱ	69.845 (14)
Ga1^v—Nd2—Ga2	114.629 (15)	Ga1^xi—Ga1—Nd1ⁱⁱ	136.657 (15)
Ga1^vi—Nd2—Ga2	114.629 (15)	Nd2ⁱ—Ga1—Nd1ⁱⁱ	135.40 (3)
Ga1ⁱⁱ—Nd2—Ga2	114.629 (15)	Nd2ⁱⁱ—Ga1—Nd1ⁱⁱ	80.566 (15)
Ga1^iv—Nd2—Ga2	145.239 (15)	Ga1^x—Ga1—Nd1ⁱ	136.657 (15)
Ga1^vii—Nd2—Ga2	145.239 (15)	Ga1^xi—Ga1—Nd1ⁱ	69.845 (14)
Ga1ⁱ—Nd2—Nd1^v	166.257 (18)	Nd2ⁱ—Ga1—Nd1ⁱ	80.566 (15)
Ga1^v—Nd2—Nd1^v	62.843 (17)	Nd2ⁱⁱ—Ga1—Nd1ⁱ	135.40 (3)
Ga1^vi—Nd2—Nd1^v	107.067 (17)	Nd1ⁱⁱ—Ga1—Nd1ⁱ	81.04 (2)
Ga1ⁱⁱ—Nd2—Nd1^v	102.794 (15)	Ga1^x—Ga1—Nd2^xv	62.33 (2)
Ga1^iv—Nd2—Nd1^v	145.533 (8)	Ga1^xi—Ga1—Nd2^xv	62.33 (2)
Ga1^vii—Nd2—Nd1^v	100.993 (16)	Nd2ⁱ—Ga1—Nd2^xv	89.70 (2)
Ga2—Nd2—Nd1^v	51.843 (9)	Nd2ⁱⁱ—Ga1—Nd2^xv	89.70 (2)
Ga1ⁱ—Nd2—Nd1ⁱⁱ	107.067 (17)	Nd1ⁱⁱ—Ga1—Nd2^xv	131.772 (15)
Ga1^v—Nd2—Nd1ⁱⁱ	102.794 (15)	Nd1ⁱ—Ga1—Nd2^xv	131.772 (15)
Ga1^vi—Nd2—Nd1ⁱⁱ	166.257 (18)	Ga1^x—Ga1—Nd1^xiv	64.73 (2)
Ga1ⁱⁱ—Nd2—Nd1ⁱⁱ	62.843 (17)	Ga1^xi—Ga1—Nd1^xiv	64.73 (2)
Ga1^iv—Nd2—Nd1ⁱⁱ	100.993 (16)	Nd2ⁱ—Ga1—Nd1^xiv	135.605 (13)
Ga1^vii—Nd2—Nd1ⁱⁱ	145.533 (8)	Nd2ⁱⁱ—Ga1—Nd1^xiv	135.605 (13)
Ga2—Nd2—Nd1ⁱⁱ	51.843 (9)	Nd1ⁱⁱ—Ga1—Nd1^xiv	79.00 (2)
Nd1^v—Nd2—Nd1ⁱⁱ	67.530 (15)	Nd1ⁱ—Ga1—Nd1^xiv	79.00 (2)
Ga1ⁱ—Nd2—Nd1^vi	102.794 (15)	Nd2^xv—Ga1—Nd1^xiv	75.74 (2)
Ga1^v—Nd2—Nd1^vi	107.067 (17)

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

Acknowledgements

The authors acknowledge Myfab Uppsala for providing facilities. We also acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, and ISIS Neutron and Muon Source (Didcot, UK) for the provision of experimental facilities. Parts of this research were carried out at PETRA III and we thank Volodymyr Baran for assistance in using beamline P02.1. Synchrotron beamtime was allocated for proposal I-20191465 EC and neutron beam time for RB2220206.

Funding information

The following funding is acknowledged: Foundation for Strategic Research (SSF) (grant No. EM16-0039); Stiftelsen Åforsk (grant No. 21-196 to Vitalii Shtender, grant No. 21-453 to Mikael S. Andersson and grant No. 22-378 to Johan Cedervall). Myfab is funded by the Swedish Research Council as a national research infrastructure. Gustav Ek acknowledges funding from the E. and K. G. Lennanders Foundation. Mikael S. Andersson acknowledges support from the Göran Gustafsson Foundation.

References

Ångström, J., Johansson, R., Sarkar, T., Sørby, M. H., Zlotea, C., Andersson, M. S., Nordblad, P., Scheicher, R. H., Häussermann, U. & Sahlberg, M. (2016). Inorg. Chem. 55, 345–352. Web of Science PubMed Google Scholar
Auer, H., Guehne, R., Bertmer, M., Weber, S., Wenderoth, P., Hansen, T. C., Haase, J. & Kohlmann, H. (2017). Inorg. Chem. 56, 1061–1071. Web of Science CrossRef ICSD CAS PubMed Google Scholar
Auer, H., Nedumkandathil, R., Häussermann, U. & Kohlmann, H. (2019). Z. Anorg. Allge. Chem. 645, 175–181. Web of Science CrossRef ICSD CAS Google Scholar
Bruker (2016). APEX3. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chapon, L. C., Manuel, P., Radaelli, P. G., Benson, C., Perrott, L., Ansell, S., Rhodes, N. J., Raspino, D., Duxbury, D., Spill, E. & Norris, J. (2011). Neutron News, 22(2), 22–25. CrossRef Google Scholar
Coelho, A. A. (2018). J. Appl. Cryst. 51, 210–218. Web of Science CrossRef CAS IUCr Journals Google Scholar
Dwight, A. E., Downey, J. W. & Conner, R. A. (1967). Acta Cryst. 23, 860–862. CrossRef ICSD IUCr Journals Web of Science Google Scholar
Ek, G., Nedumkandathil, R., Johansson, R., Montero, J., Zlotea, C., Andersson, M. S., Nordblad, P., Tang, C., Sahlberg, M. & Häussermann, U. (2019). J. Solid State Chem. 277, 37–45. Web of Science CrossRef CAS Google Scholar
Filik, J., Ashton, A. W., Chang, P. C. Y., Chater, P. A., Day, S. J., Drakopoulos, M., Gerring, M. W., Hart, M. L., Magdysyuk, O. V., Michalik, S., Smith, A., Tang, C. C., Terrill, N. J., Wharmby, M. T. & Wilhelm, H. (2017). J. Appl. Cryst. 50, 959–966. Web of Science CrossRef CAS IUCr Journals Google Scholar
Häussermann, U. (2008). Z. Kristallogr. 223, 628–635. Google Scholar
Haussermann, U., Kranak, V. F. & Puhakainen, K. (2011). Struct. Bond. 139, 143–161. Google Scholar
Höglin, V., Ångström, J., Andersson, M. S., Balmes, O., Nordblad, P. & Sahlberg, M. (2015). Results Phys. 5, 53–54. Google Scholar
Hyde, B. G. & Andersson, S. (1989). Inorganic Crystal Structures. New York: Wiley. Google Scholar
Jensen, T. R., Nielsen, T. K., Filinchuk, Y., Jørgensen, J.-E., Cerenius, Y., Gray, E. M. & Webb, C. J. (2010). J. Appl. Cryst. 43, 1456–1463. Web of Science CrossRef CAS IUCr Journals Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef ICSD CAS IUCr Journals Google Scholar
Manory, R., Pelleg, J. & Grill, A. (1978). J. Less-Common Met. 61, 293–299. CrossRef ICSD CAS Web of Science Google Scholar
Nedumkandathil, R., Kranak, V. F., Johansson, R., Ångström, J., Balmes, O., Andersson, M. S., Nordblad, P., Scheicher, R. H., Sahlberg, M. & Häussermann, U. (2016). J. Solid State Chem. 239, 184–191. Web of Science CrossRef ICSD CAS Google Scholar
Okamoto, H. (1990). Binary Alloy Phase Diagrams 2, 1829–1831. Google Scholar
Rietveld, H. M. (1969). J. Appl. Cryst. 2, 65–71. CrossRef CAS IUCr Journals Web of Science Google Scholar
Rodriguez-Carvajal, J., Roisnel, T., Daoud-Aladine, A. & Bouvet, A. (1999). Acta Cryst. A55, C262–C263. Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Shtender, V. V., Paul-Boncour, V., Riabov, A. B., Denys, R. V. & Zavaliy, I. Y. (2015). J. Solid State Chem. 229, 135–140. Web of Science CrossRef ICSD CAS Google Scholar
Villars, P., Okamoto, H. & Cenzual, K. (2018). Editors. ASM Alloy Phase Diagrams Center. ASM International, Materials Park, Ohio, USA. Google Scholar
Werwein, A., Auer, H., Kuske, L. & Kohlmann, H. (2018). Z. Anorg. Allge. Chem. 644, 1532–1539. Web of Science CrossRef ICSD CAS Google Scholar
Werwein, A., Hansen, T. C. & Kohlmann, H. (2019). Crystals, 9, 600. Google Scholar
Yatsenko, S. P., Semyannikov, A. A., Semenov, B. G. & Chuntonov, K. A. (1979). J. Less-Common Met. 64, 185–199. CrossRef ICSD CAS Web of Science Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

JOURNAL OF
APPLIED
CRYSTALLOGRAPHY

ISSN: 1600-5767

Volume 57| Part 2| April 2024| Pages 248-257

https://doi.org/10.1107/S1600576724000554

Open

access

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Search IUCr Journals		doi		Advanced search
Author		volume	page

research papers\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Revisiting the hydrogenation behavior of NdGa and its hydride phases

1. Introduction

2. Experiment

2.1. Synthesis

2.2. Thermal de­sorption experiments

2.3. Phase analysis

3. Results and discussion

3.1. Synthesis of (nearly) phase-pure NdGa and its hydrogenation/de­sorption behavior

3.2. Crystal structure variations as a function of H content

3.3. Crystal structures of NdGaD1.6 and NdGaD0.9 from NPD at 20 K

4. Conclusion

Supporting information

Acknowledgements

Funding information

References

research papers

2.2. Thermal desorption experiments

3.1. Synthesis of (nearly) phase-pure NdGa and its hydrogenation/desorption behavior

3.3. Crystal structures of NdGaD_1.6 and NdGaD_0.9 from NPD at 20 K