Analysis of cohesive energies and equation of state for high-temperature superconductors

Abstract

An expression for the potential energy as a function of volume is formulated for high- T c copper oxides by considering long-range electrostatic Coulomb interactions in the form of the Madelung energy and the short-range overlap repulsive interactions represented by the Born-Lande inverse power form. The potential parameters are determined from the Pauling's criterion based on electronic structure of atoms and from the equilibrium condition using data on unit cell volumes and bulk modulus. The parameters thus calculated are used to estimate the potential energies and cohesive energies for seventeen copper oxides under study. The potential energy expression is also used to derive the equation of state and to obtain the compression values under the effect of high pressure. The results so obtained are found to compare well with the corresponding values based on Murnaghan's equation of state.