Hydrogen site energetics in LaNi5Hn and LaCo5Hn: Toward predicting hydrides

Herbst, J.F.; Hector, L.G.
October 2004
Applied Physics Letters;10/18/2004, Vol. 85 Issue 16, p3465
Academic Journal
We have investigated the energetics of hydrogen site occupation in LaNi5Hn (hexagonal P63mc structure) and LaCo5Hn (orthorhombic Cmmm structure) via calculation of the site-dependent enthalpies of hydride formation ΔH. For each structure ΔH was determined for a broad variety of hydrogen configurations. In LaNi5Hn (LaCo5Hn) we find that the minimum ΔH occurs for hydrogen filling of the 2b6c16c2 (4e4h) sites, precisely those identified by neutron diffraction. Hydrogen-richer hydrides are predicted for both structures, in qualitative agreement with experiments performed at higher pressures.


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