Kinetics of Multicomponent Nanosize Clusters on Solid Surfaces

Abstract

We discuss the kinetics of multicomponent liquidlike clusters adsorbed onto solid surfaces. In this work, the rate expressions governing the growth and decay of surface clusters coupled to a two-dimensional gas phase are derived based on previous treatments of unary systems. General expressions are presented for the equilibrium partial pressures, the monomer evaporation rates, and the monomer capture rates. The composition dependence of the rate expressions is accomplished using the theory of real solutions to represent the activity coefficients and the surface tension. Numerical results from dynamical Monte Carlo simulations are presented for a nontrivial model of two-dimensional binary clusters. A generalized Gibbs-Thomson expression for the partial pressures is found to be in excellent agreement with the numerical results even for very small cluster sizes. The species selective evaporation rates are found to obey a simple rate law that predicts strong deviations from a naive geometric scaling behavior. The growth and decay rates of binary clusters in the simulations were accurately modeled using the analytical rate expressions.