A concise representation of adsorbate-surface interactions. II. An application to Pt(111) + Co,W(110) + Co and Pt(112) + Co systems

A method is presented to represent the chemisorptive interactions concisely. The canonical molecular orbitals of a chemisorption system are transformed into new orbitals where the charge transfer interactions between the surface and the adsorbate are maximized or minimized. The chemisorptive bonds are well described by a small number of the transformed orbitals. The analysis of chemisorptive interactions is carried out for the Pt(111) + CO, W(110) + CO and Pt(112) + CO systems. The weakening of the C-O bond in the W(110) face and in the trench region of the Pt(112) face is larger than that in the Pt(111) face in conformity with the experimental data. The interactions are, to a good approximation, represented by five or six orbitals and are explained in terms of the and donation of CO to the surface and the back donation to CO.