Study of Dielectric Properties of Covalent Crystals and Polarization Models

Investigating the Wave Functions and Cohesive Energy of Covalent Crystals

Abstract

The calculation of the cohesive energy is based on the realization that the free ion one electron wave functions of Hartree and Hartree Fock do not form an orthonormal set of wave functions when the ions come as close as they are in the solid. The correct value of the cohesive energy can be obtained as the lowest eigen value of the complete Hamiltonian of the solid.The evaluation of this value demands a knowledge of the true wave functions for the solids as a whole. These wave functions can be expressed as a linear combination of the free ion wave functions by imposing the condition of orthonormality of the linear combinations we can obtain the true wave functions corresponding to the solid.