Calculation of local density of states at defects in diamond and silicon

Abstract

A tight-binding first-principles calculation of the local density of states at lattice defects in diamond and silicon is presented. The numerical crystal potential (including a local exchange - correlation term) is fitted to a superposition of simple analytic functions centred on each atom. A basis of localised s- and p- orbitals is calculated from this potential and fitted to a combination of Gaussians. All Hamiltonian and overlap matrix elements are then analytically evaluated and the density of states and charge density can be calculated by a recursion method modified to deal with overlap. We use this method to find the charge density of the perfect lattice and the energy levels of the ideal and distorted vacancies in diamond and silicon. Finally the local densities of states along the cores of the ideal and reconstructed 90° glide partial are evaluated for diamond.