Chemisorption with overcompleteness, nonorthogonality, and electron correlation: Nondegenerate ground state

Abstract

A unified theory of hydrogen chemisorption on the surface of a metal is developed by taking overcompleteness and nonorthogonality of wave functions and electron correlation into account. The metal-atom system is described in terms of an overcomplete basis set consisting of the eigenstates (both occupied and unoccupied) of the metal and the occupied electronic state on the adatom. A pseudo-Green's-function formalism is set up to deal with the overcompleteness problem. The equations of motion of the pseudo-Green's-function elements are derived and the system energy is expressed in terms of them. The theory is applied in this paper to the situation where the intra-atomic Coulomb repulsion is assumed to be small so that hydrogen chemisorbs in a nonmagnetic configuration and the ground state is nondegenerate in spin. The Hartree-Fock approximation is worked out within the overcomplete basis, and the correspondence between our theory in this limit and previous work is established. Possible extensions of the perturbation procedure are discussed.