An ehmo study of the interaction of CO molecules absorbed on a Ni(111) surface with neighboring CO molecules, H atoms and O atoms

Abstract

The extended Hückel molecular orbital (EHMO) method has been employed to study the stability of clusters of CO, H and O on a Ni(111) surface as proposed by Marzouk, Arunkumar and Bradley [Surface Sci. 147 (1984) 477] from their recent NURS study of this system. A 25 atom nickel cluster is used to represent the metal surface, and 40 coabsorbed groups are examined. While some proposed interacting groups are found to be energetically stable, others are shown to be precursors to formation of new molecules on the surface. Stretching frequencies of the CO molecule in each of the 40 coabsorbed groups are estimated from calibration curves of computed bond orders and known axial stretching frequencies of several metal carbonyls. In most cases considered, our computed CO frequency shifts appear to be quite different from those suggested by Marzouk, Arunkumar and Bradley.