The high-pressure structural phase transition in~heavier RH3 (R: rare earth metals) by ab initio theory

Rare earth hydrides are very interesting because they exhibit a reversible metal-insulator transition upon hydrogenation. In present work, we have studied the structural stabilities of heaver~rare earth~trihydrides, RH3 (R=Sm, ..., Lu), under high pressure~using ab initio calculations. Our results show the hexagonal structure with HoD3-type structure is stable~for all studied RH3 at ambient pressure.~Further~these RH3~transform to a face-center cubic structure under high pressure. In HoD3-type phase bulk modulus decreases, whereas the~transition pressure for~hexagonal to fcc structural transformation increases,~as the atomic number of rare earth~element increases.