Cluster transport induced by a thermal gradient on a crystalline surface

Abstract

Using molecular dynamic (MD) simulations, we study the thermomigration of small clusters consisting of 2, 3 or 4 atoms on a crystalline surface. After evidencing the thermomigration by analyzing the cluster trajectories, we generalize the thermodynamic integration method to compute a thermodynamic potential driving the probability of presence of the clusters on a substrate submitted to a thermal gradient. The study of this thermodynamic potential allows to disentangle the thermomigration effective force from the stochastic diffusion. We show that the heat of transport characterizing the effective force responsible for thermomigration is the sum of the free energy of the cluster–substrate and cluster internal energies. Finally, an unidimensional kinetic model for the thermomigration is proposed and its results compared to the MD trajectories.