High-pressure induced structural phase transition in alkaline earth CaX (X = S, Se and Te) semiconductors: NaCl-type ( B1) to CsCl-type ( B2)

• Published in: Journal of alloys and compounds 2009-09, Vol.484 (1), p.239-245
• Main Authors: Varshney, Dinesh, Rathore, V., Kinge, R., Singh, R.K.
• Format: Article
• Language: English
• Subjects: Elastic constants; Equation of state; Phase transition; Volume collapse
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2009.04.022

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.