Eur. Phys. J. B 84, 99-108 (2011)
https://doi.org/10.1140/epjb/e2011-10857-y

Regular Article

High pressure phase transition and elastic behaviour of lanthanum monochalcogenides

¹ Condensed Matter Theory Group, School of Studies in Physics, Jiwaji University, 474011 Gwalior, India
² Department of Physics, Govt. K.R.G. P.G. Autonomous College, 474001 Gwalior, India

^a e-mail: sosfizix@gmail.com

Received: 9 November 2010
Received in final form: 29 July 2011
Published online: 3 November 2011

Abstract

The Phase transition and elastic properties of La-monochalcogenides have been investigated under pressure by means of a modified charge-transfer potential model which incorporates the Coulomb interaction modified by Coulomb screening due to the delocalization of electron of rare-earth atom leading to many-body interactions, covalency effect and overlap repulsion extended up to second-nearest neighbours. Under high pressure the coordination increases and they transform from rock-salt to CsCl structure. The calculated values of cohesive energy, lattice constant, phase transition pressure, relative volume collapse, harmonic and anharmonic elastic moduli and their first- and second-order pressure derivatives agree well with the available measured data and better than those computed by earlier workers. Present model is capable of explaining the Cauchy’s discrepancy correctly.