Microscopic physics diffusive modes

Sintering is an important mode of deactivation in supported metals that involves complex microscopic physical and chemical phenomena, e.g., dissociation, emission, diffusion, and capture of metal atoms and crystallites. The relative importance of these different processes may change with reaction conditions and catalyst formulation. Modeling and prevention of sintering processes require an understanding of these basic processes as well as quantitative measurements of sintering rates. 

A microscopic calculation of the size-dependent diffusion is presented here. The calculation is based on the well-known mode coupling theoretical approach. The theoretical calculation is shown to give an excellent agreement with the simulation results and provides a physical interpretation of the enhanced diffusion. It is found that the enhanced diffusion of smaller solutes arises from the decoupling of the solute motion from the density mode of the solvent. 

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