Abstract
The present paper addresses the pressure-induced structural aspects of NaCl-type ( B1) to CsCl-type ( B2) structure in alkaline earth chalcogenides (AECs) calcium chalcogenides (CaX; X = S, Se and Te) by formulating an effective interionic interaction potential (EIoIP) with long-range Coulomb interactions and the Hafemeister and Flygare type short-range overlap repulsion extended upto the second neighbor ions and the van der Waals (vdW) interaction. The vdW coefficients are evaluated 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 structural transition ( B1 to B2 structure), the phase transition pressures ( P t ) of 40 (CaS), 38 (CaSe) and 34 (CaTe) GPa as well the elastic properties. The calculated values of the volume collapses [Δ V( 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. The Born and relative stability criteria is valid in Ca monochalcogenides.
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