Van der Waals coefficients and cohesive energies of lead chalcogenides

Abstract

The cohesive energies of PbS PbSe and PbTe, having NaCl type of crystal structure, are calculated using the generalized Huggins-Mayer form (GHM) for the Born repulsion energy. The van der Waals interactions (VDW) are estimated from the London and Mayer formulae and compared with those estimated from the Slater-Kirkwood variational method. The cohesive energies calculated adopting the VDW coefficients calculated from the later method are in good agreement with the experimental values. The difference between the experimental cohesive energies and the calculated, assuming variational method, are 2·26, 2·97 and 3·75 eV respectively for PbS, PbSe and PbTe which are in good agreement with the reported values for the covalent bonding correction using Heitler-London-Lowdin method (HLL) which are respectively 2·1, 2·9 and 3·3 eV (Tanaka and Morita 1979).