Convergence of Reciprocal-Lattice Expansions and Self-Consistent Energy Bands of NaF

Abstract

A convergence study is made of the reciprocal-lattice expansion of linear-combination-of-atomic-orbitals integrals in NaF. Converged integrals are obtained by direct summation and by extrapolation after different numbers of terms. It is found that extrapolation procedures give simple accurate results and substantially reduce labor involved. Comparison is made with other methods for obtaining convergence. Converged integrals are used as a basis for a self-consistent Hartree-Fock-Slater energy-band calculation for NaF using methods previously developed. Some transition energies are presented and correlated with available optical data. Self-consistent charge densities in NaF differ only slightly from a linear combination of ionic charge densities, confirming the ionic nature of NaF.