Study of phase stability and isotope effect in dysprosium trihydride at high pressure

Synchrotron X-ray and Raman scattering investigations have been performed on dysprosium trihydride at high pressure up to 40 GPa. Structural phase transformation from original hexagonal to cubic phase has been observed confirming predictions from other studies and theoretical calculations. Dysprosium trihydride is the last one that has not been studied so far among the heavier lanthanide trihydrides family. These studies completed the overall picture of hexagonal to cubic phase transition for the whole ReH₃ compounds. Equation of state and Gruneisen mode parameters have been calculated. High pressure Raman scattering performed on dysprosium deuteride unveiled significant deviation from the harmonic approximation in specific modes most probably due to the anharmonicity of hydrogen potential in the hydride lattice. - Highlights: • Pressure induced phase transition from hcp to fcc has been characterized. • Raman scattering of dysprosium trihydride and trideuteride has been used for constructing of phase diagram. • Isotope effect has been estimated for selected Raman modes under pressure.