Elasticity and Thermodynamic Properties of EuS Related to Phase Transition

First-principles calculations of the crystal structures, phase transition, and elastic proper-ties of EuS have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values are in very good agreement with experimental data as well as some of the existing model calculations. The dependence of the elastic constants, the aggregate elastic modulus, and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson's ratio, Debye temperature, and the compressional and shear elastic wave velocities with pressure have been investigated for the first time. Through the quasi-harmonic Debye model, the thermal expansions, heat capacities, Grneisen param-eters and Debye temperatures dependence on the temperature and pressure are obtained in the pressure range from 0 GPa to 60 GPa and temperature range from 0 K to 800 K.