On the theory of chemisorption
A solution of the Anderson model for chemisorption including correlation effects is presented. The solution becomes exact in three limiting cases (largeU, smallU i.e. Hartree-Fock and the so-called symmetric strong coupling limit) of the intra atomic Coulomb repulsionU and the hopping termV. Excellent agreement of our approximation with Schrieffer's exact numerical results for the binding energy of a small model system is found. Our results for the binding energy and the charge of the adsorbate show a significant improvement over the Hartree-Fock approximation. The single particle spectral density of the H-F approximation turns out to be even qualitatively wrong in the largeU strong coupling limit.