MOLECULAR-DYNAMICS STUDY OF THE SURFACE-DIFFUSION OF LARGE ADSORBATES.3. ROLE OF ADSORBATE SHAPE

The present study is dedicated to the investigation of the relationshi p between the surface diffusion mechanism of large adsorbates and the adsorbate shape. Three different shapes of model adsorbates were exami ned: linear chains, branched chains, and cyclic molecules. It was foun d that the surface diffusion mechanism of linear and branched chain ad sorbates is quite similar, while a markedly different diffusion mechan ism is observed for cyclic adsorbates. For all types of adsorbates the temperature dependence of the diffusion coefficient was found to obey an Arrhenius expression. The results of the simulations have shown go od qualitative agreement with the available experimental data.