BENZENE ADSORPTION ON PT(111) - A THEORETICAL-STUDY

From crystal orbital calculations, benzene is found to chemisorb with nearly equal binding energy on a hollow site and on a bridge site of t he Pt(111) face. The chemisorption is stronger and involves larger mol ecular distortions than on palladium and rhodium surfaces in agreement with experiment. On the hollow site, the benzene molecule undergoes a Kekule distortion. On the bridge site found experimentally (with or w ithout coadsorbed CO), the benzene molecule undergoes a local C-2u dis tortion with long and short C-C bonds also in qualitative agreement wi th experiment. The favored azimuthal orientation of pure benzene coinc ides with that found experimentally only in the presence of CO. Accord ing to calculations, CO adsorption is found to weaken the benzene adso rption and reduce its metal-induced distortions but preserved the same orientation.