Diffusion of adsorbed molecules on solid surfaces

We have conducted molecular-dynamics (MD) simulation studies of diffusion in a series of physically adsorbed n-alkanes on a model Pt(ll I) surface. In addition, we have used transition-state theory (TST) to estimate diffusion-energy barriers for these molecules and to determine the characteristic mechanisms by which they diffuse. The combined studies yield insight into the relationship between molecular structure, size, and mobility. Ocr studies also reveal some of the unique features associated with molecular mobility, including: unique, one-jump mechanisms for molecular hopping between non-nearest-neighbor binding sites; conformational correlation in molecular hopping; and short-ranged, directional anisotropy in diffusion induced by the molecular degrees of freedom. We discuss some experimental ramifications of these unique features.