THEORY OF CARBON-MONOXIDE ADSORPTION ON NIAL(110)

We present results of a model Hamiltonian approach to CO single molecule adsorption on a semi-infinite NiAl (110) surface. CO adsorbs on the Ni rows in agreement with experimental findings. The calculated electron-hole excitation spectrum compares reasonably with direct and inverse photoemission data. The nature of the chemisorption bond is analyzed by partitioning the density matrix and the energy into components which are accessible to physical intuition. The results demonstrate that the d electrons are as important on the alloy as they are on the pure Ni component, although they play a different role. The extended nature of the alloy d wave functions determines the adsorption geometry. The character of the chemisorption bond is discussed in comparison to CO adsorption on the components Al and Ni and to CO/Cu.