Pressure induced hexagonal to cubic phase transformation in erbium trihydride

High-pressure X-ray diffraction studies of erbium trihydride have been carried out in a diamond anvil cell up to 30 GPa at room temperature. Structural phase transformation from hexagonal to cubic phase has been detected at a pressure of about 15 GPa. The molar volume of ErH3 as a function of pressure has been fitted with Murnaghanʹs equation of state. Bulk modulus Bo and its pressure derivative Bo′ have been determined for both phases. The lattice parameter of the new, cubic phase was determined as equal to 5.23 Å at normal pressure. The volume change accompanied by the phase transition has been calculated.