Thermo-elastic and structural properties of thorium chalcogenides: A high pressure study

The pressure induced phase transition and thermo-elastic properties of Th-chalcogenides have been investigated by means of two different models (i) modified charge-transfer potential model which consists of Coulomb and Coulomb screening due to delocalization of f  -electron of the rare-earth atom and modified by covalency and zero-point energy effects and repulsive interactions, and (ii) charge-transfer model which excludes covalency and zero-point energy effects in the previous model. These materials lie in Fm3¯m phase at ambient conditions and transform to Pm3¯m phase under pressure due to first-order phase transition (PT = 24.75 and 14.34 GPa) and their equation of state show volume collapse of 8.92 and 9.13%, respectively for ThS and ThSe while ThTe retains Pm3¯m phase up to 50 GPa. Our results are in good agreement with the experimental data. The elastic and thermal properties of these compounds have also been computed at normal and high pressures. Both the models are capable of explaining the Cauchy’s discrepancy, elastic, phase transition and thermophysical properties successfully.

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