High pressure structural (B1–B2) phase transition and elastic properties of II–VI semiconducting Sr chalcogens

We evolve an effective interionic interaction potential (EIoIP) with long-range Coulomb interactions and the Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and the van der Waals (vdW) interaction to discuss the pressure induced structural aspects of NaCl-type (B1) to CsCl-type (B2) structure in alkaline earth chalcogenides (SrX; X = S, Se and Te). Particular attention is devoted to evaluate the vdW coefficients following the Slater–Kirkwood variational method, as both the ions are polarizable. The present calculations have revealed reasonably good agreement with the available experimental data on the phase transition pressures (P_t = 17.5, 14.5, 12.5 GPa) and the elastic properties. The calculated values of the volume collapses [ΔV(P)/V(0)] are also closer to their observed data. Further, the variations of the second- and third-order elastic constants with pressure have followed a systematic trend, which are almost identical to those exhibited by the observed data measured for other semiconducting compounds with rocksalt (B1) type crystal structure. Also the Born and relative stability criteria is valid in strontium monochalcogenides.