Ageing of out-of-equilibrium nanoalloys by a kinetic mean-field approach

Abstract

This study describes the ageing of bimetallic nanoparticles using a kinetic mean-field method which provides the time evolution of the concentration for each site. We consider the cuboctahedron of 309 atoms in the Cu–Ag system, which is a prototype of systems with a strong tendency to phase separate. Starting from an initial homogenous configuration, we investigate the evolution towards the equilibrium configuration at different temperatures. Surprisingly, at low temperature, the kinetics exhibits a first transition towards an onion-like configuration followed by a second transition towards the equilibrium core–shell configuration. An analysis of the kinetics of the formation and then of the dissolution of the onion-like structure allows us to identify the main paths of the kinetic process.