Approximate Numerical Hartree—Fock Method for Molecular Calculations

Abstract

Calculations are presented which show that the atomic orbitals which result from approximate numerical Hartree—Fock calculations (by the Xα method) are as close to the Hartree—Fock limit for atoms as are those calculated using a double‐zeta basis. Arguments are given which show that the exchange is treated with sufficient accuracy by the Xα method. With the additional ``muffin‐tin'' approximation, which is widely used in solid state calculations, the ``multiple scattering'' formalism can be used for molecules to solve this model Hamiltonian without any further approximation. The exchange is treated with sufficient accuracy, therefore this approach should give the electronic energies as well as the usual type of ab initio calculation, whenever the ``muffin‐tin'' approximation is good, but with 2 or 3 orders of magnitude less computational time.