Consecutive Peierls distortions and high-pressure phase transitions in YH_3

摘要

High-pressure phase transformations in YH_3 were investigated using the evolutionary algorithm for structural searches. A series of phase transformations are predicted with three lowest enthalpy phases identified. Two consecutive Peierls distortions within the hcp and fcc cells result into two low-pressure structures, the previously identified P3c1 structure and a predicted C2/m structure. The P3c1 structure transforms to a C2/m structure at 12 GPa and stabilizes to a fcc structure at 38 GPa. The predicted properties of the C2/m structure agree well with experimental observation. At 200 GPa, the fcc structure transforms to a hcp structure. At 214 GPa, a transformation analogous to a Burgers deformation becomes more favored in the hcp form and this results in a stable Cmcm structure.