HYDROGENATION OF ZR6FEAL2 AND CRYSTAL-STRUCTURE OF ZR6FEAL2D10

The intermetallic compound Zr6FeAl2 was hydrogenated (deuterated) at room temperature and investigated by X-ray and neutron powder diffraction. The hydride (deuteride) crystallizes with hexagonal symmetry (space group P ($) over bar 62c; deuteride: a = 8.1354(4) Angstrom, c = 7.0940(6) Angstrom, V = 406.62(5) Angstrom(3), Z = 2, refined composition Zr6FeAl2D9.82(3)). Its metal atom substructure derives from an ordered Fe2P type host structure (space group P ($) over bar 62m) by small atomic displacements that lead to a doubling of the c axis. Deuterium occupies two types of tetrahedral [Zr-4], one type of tetrahedral [Zr3Fe] and one type of trigonal bipyramidal [Zr3Fe2] interstices, thus avoiding the neighbourhood of aluminium. The metal-deuterium bond distances are in the range Zr-D = 2.03-2.22 Angstrom and Fe-D = 1.73-1.77 Angstrom, while the shortest A1-D distance is 2.90 Angstrom. The hydrogen sorption properties of Zr6FeAl2 are intermediate to those of Zr2Fe and Zr2Al.