The effective quasiparticle potential in molecules and solids

Abstract

The Wigner-Seitz potential is used as an effective quasiparticle potential to find the binding energies and excitation energies of diatomic molecules and diamond. The single-particle Schrödinger equation is solved by the matching Green function method; with the Wigner-Seitz potential the binding energy can be found from the sum of one-electron eigenvalues. Good results are obtained for the binding energies of alkali molecules, but the method is poor in the case of H₂ where the effective potential is much closer to Hartree-Fock. The Wigner-Seitz potential gives satisfactory energy levels in multiply bonded molecules such as C₂, N₂ and CO, and in the covalent diamond crystal it gives a good band structure and binding energy.