Chemisorption with overcompleteness, nonorthogonality, and electron correlation: II. Large U limit

The pseudo-Green's-function theory of hydrogen chemisorption, developed in a previous paper, is extended to treat the situation when the intra-atomic Coulomb repulsion on the adatom is very large, so that hydrogen chemisorbs in a magnetic configuration. The theory takes systematically into account the overcompleteness and nonorthogonality of wave functions describing the problem, and electron-electron interaction. The metaladsorbate 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. The overcompleteness problem is satisfactorily dealt with through the introduction of the pseudo Green's functions, and their equations of motion are worked out in detail. In the limit of a large intra-atomic Coulomb repulsion U, there is an electronic spin localized on the adsorbed hydrogen atom. This is shown by rearranging the equations of motion of the pseudo Green's function in that case, so that they manifestly describe the scattering of metal electrons off of the localized spin. The physics of hydrogen chemisorption in this limit is discussed, and comparison is made with previous theoretical work.