MO STUDY OF CO CHEMISORPTION AND OXIDATION ON A PT(100) SURFACE

Using an atom superposition and electron delocalization molecular orbi tal (ASED-MO) method, we have investigated the vibrational and chemiso rptive properties of adsorbates on a Pt(100) surface during CO oxidati on. The calculated vibrational stretching frequency for a predicted st ructure of [CO...O] complex is 1642 cm(-1). The CO bond stretches by 0.05 Angstrom when adsorbed on one-fold site, and is tilted by 30 Angs trom from the surface normal. We find the decrease in CO vibrational f requency on going from the one-fold to the high coordination sites. Bi nding at the two-fold site is predicted to be favored for Pt-18(100) a nd at the 1-fold site for Pt-23(100). From the calculations of the ste ric interactions, we have found that pre-adsorbed oxygen modifies the surface so that CO is adsorbed on the one-fold site ordered in a (root 2X root 2)R45 degrees. Our results are in good agreement with recent experimental findings of Hong et al. [J. Phys. Chem. 1993, 97, 1258].