The pressure and temperature dependent elastic properties of mercury chalcogenides ( Hg X; X = S , Se and Te ) with pressure induced structural transition from ZnS -type (B3) to NaCl -type (B1) structure have been analyzed within the framework of a model interionic interaction potential with long-range Coulomb and charge transfer interactions, short-range overlap repulsion and van der Waals (vdW) interactions as well as zero point energy effects. Emphasis is on the evaluation of the Bulk modulus with pressure and temperature dependency to yield the Poisson's ratio ν, the Pugh ratio ϕ, anisotropy parameter, Shear and Young's modulus, Lamé's constant, Klein man parameter, elastic wave velocity and Debye temperature. The Poisson's ratio behavior infers that Hg X are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of Hg X and still awaits experimental confirmations.
