LaH2

LaH2 is a binary hydride of lanthanum, consisting of lanthanum and hydrogen in a 1:2 ratio. It is one of several hydride phases that can form in the lanthanum–hydrogen system. As a metal hydride, LaH2 is typically studied for its basic structural chemistry and potential hydrogen storage properties.

Crystal structure and bonding: In many metal dihydrides, including reported descriptions of LaH2, the stable phase at ambient pressure is described as fluorite-type, with lanthanum forming a face-centered cubic lattice and hydrogen occupying tetrahedral interstitial sites. This arrangement gives a high hydrogen content and a metallic bonding character that influences its electrical and mechanical properties.

Synthesis and stability: LaH2 can be produced by direct hydrogenation of lanthanum metal under elevated temperature and hydrogen pressure, or by conversion from other lanthanum hydride phases under controlled conditions. The compound is typically air-sensitive, and exposure to air can lead to oxidation and changes in composition over time. Its stability is strongly dependent on temperature and hydrogen chemical potential.

Properties and potential applications: LaH2 is expected to exhibit metallic conductivity typical of many metal hydrides. Its practical use in energy storage is limited by stability considerations and by its tendency to transform to other hydride phases as conditions change. It remains of interest primarily within basic research on the La–H phase diagram and as a stepping stone to understanding higher lanthanum hydrides.

Relation to other lanthanum hydrides: The lanthanum–hydrogen system includes several phases, such as LaH3 and higher hydrides like LaH10 observed under extreme pressures. Studying LaH2 helps researchers explore hydrogen absorption, phase stability, and the prospects of superconductivity in related hydrides under pressure.