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The crystal structures of LiND2 and Mg(ND2)2 have been investigated by high-resolution powder neutron and synchrotron X-ray diffraction. LiND2 takes a tetragonal crystal structure (space group I4¯, a = 5.03164(8) A, c = 10.2560(2) A). The Li+ ions are tetrahedrally coordinated by four amide (ND2−) ions with Li–N separations ranging between 2.065(3) and 2.210(3) A. The two N–D distances are similar (0.967(5) and 0.978(6) A) and the D–N–D angle is 104.0(7)°, which are very close to the isoelectronic water molecule. The neutron diffraction data for Mg(ND2)2 are fitted well with a tetragonal unit cell (space group I41/acd, a = 10.3758(6) A, c = 20.062(1) A), although the powder synchrotron X-ray diffraction data indicate that the symmetry may be lower. The cation is again tetrahedrally coordinated by four amide ions. The Mg–N distances are between 2.00(1) and 2.17(1) A. The N–D separations and D–N–D angles in the three different amide ions are in the range of 0.95(1)–1.07(1) A and 101(1)–107(2)°, respectively. The Mg(ND2)2 structure can alternatively be described as a pseudo-fcc lattice of Mg4 tetrahedra with amide anions in all tetrahedral interstices and six amide ions distributed in the periphery of each octahedral interstices, giving a slightly distorted octahedral arrangement of amide units around each Mg4 tetrahedron.

The mixed alanate K2NaAlH6 has been synthesised by ball-milling a mixture of KH and NaAlH4 and subsequent annealing at 150 °C under a stabilizing hydrogen pressure. It takes a cubic ordered perovskite-type structure (space group F m 3 ¯ m , a = 8.118(1) A) where the ideal octahedral AlH63− units form a cubic close-packed structure with K+ in all tetrahedral sites and Na+ in all octahedral sites. K2NaAlH6 with 1 mol% TiF3 decompose quickly and reversibly with a flat plateau. Pressure-composition isotherms have been measured at five temperatures in the range 280–325 °C. The decomposition enthalpy and entropy were determined to 98(2) kJ/mol H2 and 150(4) J/(K mol H2) from the van’t Hoff equation.

The crystal structure of rhombohedral PbNb2O6 is re-examined by powder XRD and powder neutron diffraction in combination with ab initio DFT calculations.

Mechanochemical milling of LnCl3 (Ln: La—Tb, Er, Yb, Lu) with LiBH4 in the molar ratio of 1:6 for 5 h and additional annealing at 100 °C for 50 h leads to the new compounds LiLn(BH4)3Cl (Ln: La, Ce, Pr, Nd, Sm, Gd), Ln(BH4)3 (Ln: Sm, Gd, Tb, Er, Yb), and/or LiLn(BH4)4 (Ln: Yb, Lu).

The title compounds are characterized by neutron and X-ray diffraction, and IR spectroscopy.