Kohn—Sham bond lengths and frequencies calculated with accurate quadrature and large basis sets

Abstract

We report calculations of bond lengths and frequencies using Kohn—Sham theory, defined as replacing the exchange term in the Hathree—Fock self-consistent field procedure by potentials of density functional theory. Several functionals are tested including the local density approximation to the exchange energy. Becke's non-local correction to the exchange, the Vosko—Wilk—Nusair functional for correlation with Perdew's non-local correction to the correlation energy and the Lee—Yang—Parr correlation functional. High accuracy quadrature is used, which enables the gradient of the energy to be calculated straightforwardly. The results are compared to Hartree—Fock theory and to hydrid DFT methods based on the Hartree—Fock density. On average, bond lengths from the hybrid method are much better than SCF bond lengths, and often better than those from second-order Møller—Plesset theory. The Kohn—Sham bond lengths are rather long, but improve as the basis set is increased, and for large basis sets bond lengths, dipole moments and frequencies appear on to be a significant improvement over SCF theory.