Regular Adsorption of Co Molecules On Lif(001)

The regular adsorption of CO at various concentrations on an infinite three-layer slab of LiF has been studied by using the CRYSTAL ab initio program. The CO molecules are adsorbed vertically above the surface cations by purely electrostatic attraction counterbalanced by the Pauli repulsion. The induced polarization has been analysed through the changes occurring in the molecular orbitals of the adsorbed species. The adsorption via the oxygen atom appears to be preferred, which contradicts IR experimental data. Such contradiction arises from the correlation error in the Hartree-Fock SCF method which is applied in the CRYSTAL program. Consideration of simple correlated clusters enables a semi-quantitative evaluation which additively corrects the above contradictory results.