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LaPtIn was attempted hydrogenated at a hydrogen pressure of 182 bar and temperatures from room temperature to 673 K. The crystal structure of the resulting LaPtInH 0.53 hydride was determined from powder neutron diffraction data. The structure was indexed on an expanded LaPtIn intermetallic unit cell with space group P 6 ¯ 2 m and dimensions a = 7.8229(2) A and c = 4.1647(2) A. Hydrogen occupies tetrahedral 4h sites in such a way that tetrahedral voids sharing a common face are not simultaneously populated. The result could not support previous density-functional theory calculations regarding the hydrogen absorption capacity of LaPtIn [P. Ravindran, P. Vajeeston, R. Vidya, A. Kjekshus, H. Fjellvag, Phys. Rev. Lett. 89 (2002) 106403].

KAlD 4 was synthesized from LiAlD 4 , AlEt 3 and KF in Et 2 O. The crystal structure was determined from powder neutron diffraction data at 8 and 295 K. KAlD 4 takes the same structure as BaSO 4 and KGaD 4 with space group Pnma and unit-cell dimensions a = 885.15 (14) pm, b = 581.19 pm (8), c = 734.57 (11) pm at 295 K. The crystal structure consists of isolated, nearly ideal, AlD 4 − tetrahedra with K + in 10-coordinated sites in-between. The average Al–D distance is 161.8 pm.

Two hydrogenated intermetallics with the highest Al/Zr ratio among the hydrogen-absorbing Zr–Al compounds, Zr 4 Al 3 and Zr 3 Al 2 , have been studied by synchrotron X-ray, powder neutron diffraction and thermal desorption spectroscopy. Initial intermetallic compounds are quite different with respect to Al–Al interactions and contain plain Kagome Al nets (Zr 4 Al 3 ) or Al–Al pairs (Zr 3 Al 2 ). In hexagonal Zr 4 Al 3 D 2.68 (space group (s.g.) P 6 3 22; a =11.0017(4); c =11.1694(5) A) a 2 a ×2 a ×2 c superstructure is formed as a result of deuterium ordering in half of the available Zr 4 tetrahedra. These tetrahedra share common corners and edges and form layers separated by 6363 Al-nets. In tetragonal Zr 3 Al 2 D 2.26 (s.g. P 4 2 / mnm ; a =7.5970(3); c =7.2613(3) A) in addition to the completely filled Zr 4 tetrahedra hydrogen partially occupies Zr 3 triangular sites. Thermal stability of the studied deuterides and Zr–D bonding characteristics can be related to the size of the occupied Zr 4 tetrahedra. Higher thermal stability of Zr 3 Al 2 D 2.26 agrees well with the existence of large Zr 4 sites and contrasts to the behavior of Zr 4 Al 3 D 2.68 containing ‘contracted’ Zr 4 tetrahedra and having weaker Zr–D bonds.

The recent powder neutron diffraction study of the crystal structure of LaNiInD 1.22 [J. Alloys Comp. 330–322 (2002) 132] concluded on the formation of a D…D pair with an unusually short interatomic distance of 1.63 A. Hydrogen atoms in LaNiInD 1.22 occupy a single crystallographic site and are coordinated by face-sharing La 3 Ni tetrahedra (92% occupancy). PCT measurements show that hydrogen storage capacity of LaNiIn, 1.63 at.H/formula unit, exceeds the limit of 1.33 at.H/LaNiIn when the La 3 Ni sites are completely occupied. In the present work, in situ powder neutron diffraction data were collected under D 2 pressure of 4.6 bar in order to study the deuteride with a maximum D content in the metal matrix. In the hexagonal structure of LaNiInD 1.63 (space group P 6 2 m ; a =7.3874(4); c =4.6816(2) A) Rietveld refinements showed that deuterium atoms occupy 36% of the available distorted La 3 NiIn 2 octahedra, in addition to the 96% filled La 3 Ni sites. The structure of LaNiInD 1.63 represents the first example of a deuteride containing direct In–D bonds (2.346(2) A). H bonding to the La 3 NiIn 2 sites is rather weak and a desorption from these sites takes place at room temperature and hydrogen pressures below 1 bar.

The structure of Li 3 AlD 6 has been determined by combined synchrotron X-ray and neutron diffraction. The space group is R 3 with unit-cell dimensions a =8.07117(10) and c =9.5130(2) A. The structure consists of isolated and close to regular AlD 6 3− octahedra, which are connected via six-coordinated Li. The Al–D distances are 1.734–1.754 A, and the Li–D distances are 1.892–2.120 A. The shortest D–D distance of 2.395 A is found within the octahedra. The structure can be described as a distorted bcc structure of AlD 6 3− units with all tetrahedral sites filled with Li.

The deuterides Zr 3 V 3 B 0.24 O 0.36 D 8.0 and Zr 3 V 3 B 0.40 O 0.60 D 6.4 with cubic structures [space group Fd 3 m (No. 227)] related to η 1 - (Fe 3 W 3 C) type have been studied by powder X-ray and neutron diffraction. The transition from the alloys to the corresponding deuterides gives a redistribution of the O/B atoms between two available types of zirconium octahedra, from 16 d (1/2, 1/2, 1/2) into the 8 b (7/8, 3/8, 7/8) sites. A correlation between occupancy/vacancy of the Zr 6 octahedra and the structure of the deuterium sublattice has been established. This explains the significant differences between the deuterides studied in this work and the previously reported, chemically similar Zr 3 V 3 OD 4.93 .

Compositions in the range Zr3V3B0.12–0.40O0.18–0.60 from the Zr–V–B2O3 system have been subjected to metallographic characterisation, microprobe analysis and powder neutron diffraction. On melting, boron was found to be reduced from its oxide and in the annealed condition, it was identified as a constituent of two phases, η-oxyboride Zr3V3(B,O) and vanadium boride V3B2. Hydrogen absorption–desorption properties were studied and related to the phase and structural composition of the alloys. A redistribution of the light atoms (oxygen, boron) within the η-oxyboride Zr3V3(B,O) matrix and, also, between the constituent phases of the alloys takes place during high temperature cycling in hydrogen which could indicate increased lattice mobility of these non-metallic elements in the hydride material.

The ferromagnetic ordering of the Heusler-related alloy AuMnSn has been verified by powder neutron diffraction. The cubic AlLiSi-type crystal structure of AuMnSn [a=634.12(11) pm at 298 K, Au in 4c, Mn in 4b, Sn in 4a of F43m] has been confirmed. Contrary to the indications from the preceding single-crystal X-ray diffraction study of AuMnSn the powder neutron diffraction data gave no evidence for intermixing of Mn and Sn on the 4b and 4a sites. The ordered magnetic moments are confined to the Mn atoms and their size at 298 K is μF,Mn=3.62(7) μB.