Surface diffusion potential energy surfaces from first principles: CO chemisorbed on Pt{110}

Abstract

Lateral potential energy curves for the chemisorption of CO on Pt{110} (1×1) and (1×2) along different azimuthal directions have been calculated using density functional theory slab calculations. In contrast to the simple models almost universally used, the results along 〈11̄0〉 show that there is a barrier of ∼0.15 eV between bridge and atop sites. Both bridge and atop sites are local minima. Diffusion along 〈100〉 on the (1×1) surface is strongly inhibited by a barrier ⩾1.2 eV. Quasielastic helium atom scattering data require reanalysis in the light of these results. The free energy, determining the most stable site at finite temperatures, includes a significant vibrational entropy term in the atop site.