Theoretical analysis of pressure-induced phase transition of EuS and EuSe including the role of temperature

An effective interaction potential is developed to study the high-pressure phase transition of EuS and EuSe having NaCl-type (B1) structure at room temperature. The three-body interaction potential (TBIP) includes long-range Coulombic, three-body interaction forces, short-range overlap repulsive forces operative up to next nearest neighbor ions, van der Walls interactions and zero point energy effects. We are incorporating temperature effects in three body potential model for the first time and this has made TBIP more realistic. Earlier theoretical studies of phase transition with TBIP model have been carried by assuming the equilibrium at 0 K instead of room temperature. We have theoretically investigated phase transition pressures, volume collapses and elastic behavior of EuS and EuSe at room temperature and found results well suited with available experimental data. This shows that the inclusion of temperature effects in TBIP makes the present model suitable for theoretical high-pressure studies.