High pressure phase-transition, elastic and thermal properties of uranium chalcogenides: A model study

Uranium chalcogenides crystallize in Fm3¯m space group at ambient condition and transform to Pm3¯m space group under pressure. We have investigated the elastic and thermo-physical properties of uranium mono-chalcogenides using modified charge-transfer potential model. This model incorporates long-range Coulomb effects and charge-transfer (Coulomb screening due to f-electrons of U) effect modified by covalency and short-range repulsive interaction extended up to next-nearest neighbours. This model is capable of explaining the Cauchy-discrepancy. Calculated values of the phase-transition pressure (PT = 79.50, 19.60 and 9.50 GPa) and relative volume collapse (4.69, 7.95 and 7.88%) are in good agreement with experimental data. The equation of state has been plotted to get phase diagram.