Cyclic cluster model for calculating defects in solids using the local density approximation

Abstract

The cyclic cluster model (CCM) was introduced earlier for defect calculations in the framework of semi-empirical quantum chemical methods with only two-centre interactions. The CCM represents a good balance between an approximate description of localized and extended states, offering most of the advantages of supercell methods at the cost of a molecular cluster calculation. This paper presents the adaptation of the CCM to an ab initio density functional Hamiltonian, incorporating the local density approximation, norm-conserving pseudopotentials and a Gaussian basis. Test results on perfect diamond cyclic clusters illustrate the advantages of the CCM.