An efficient numerical multicenter basis set for molecular orbital calculations: Application to FeCl₄

The use of numerical solutions to atomlike single site potentials as a basis for molecular orbital calculations is investigated. The atomic Hamiltonian is modified by addition of a potential well to induce additional discrete levels with the desired spatial characteristics. The discrete variational method is employed, in the Hartree-Fock-Slater model, to compare levels obtained for FeCl4 using multiple-scattering, conventional Slater-orbital, and numerical basis sets. The numerical technique is shown to be an accurate and efficient method for treating general (non-muffin-tin) molecular potentials. The errors in energy levels due to the muffin-tin approximation are calculated.