Petrova N. Modeling of gas adsorption on transition metal surfaces

The results of modeling of gas adsorption on transition metal surfaces are presented. Main attention is focused on hydrogen adsorption on (110) W and Mo surfaces, on the structures and adsorption kinetics of oxygen and CO on Pt(111) and on the catalytic CO oxidation. Kinetics of low-temperature hydrogen and deuterium adsorption on W(110) and Mo(10) surfaces have been studied by the "real-time" Monte Carlo simulations. The role of the intrinsic and extrinsic precursor states in hydrogen dissociative adsorption on the transition metal surfaces is analyzed. Recently reported qualitative dependence of the adsorption characteristics on variation of the H2 flux is described in terms of the dynamical equilibrium between incident and desorption fluxes and improved conditions for accommodations for the hydrogen molecules at high incident fluxes. One of the main aspects in the modeling is an adequate account of lateral interaction of adsorbed particles, which includes both direct (electrostatic and exchange) andindirect (through substrate electrons) interactions. In particular, proper account of the lateral interaction has allowed for explanation of the mechanism of formation of the CO and oxygen structures on the Pt(111) surface. A new model of catalytic CO oxidation reaction, in which only oxygen atoms in hcp-type threefold adsorption sites on the Pt(111) surface are chemically active, is suggested. Within this model, the TPD spectra of the coadsorbed CO+O films, which represent the rate of CO oxidation, do resemble experimental data for a perfectly ordered p(2x2) structure of CO+O/Pt(111) film as well as for the film with structural imperfections.