Finite-size effects in the dynamics and thermodynamics of two-dimensional Coulomb clusters

Abstract

The dynamics and thermodynamics of melting in two-dimensional Coulomb clusters is revisited using molecular dynamics and Monte Carlo simulations. Several parameters are considered, including the Lindemann index, the largest Lyapunov exponent, and the diffusion constant. In addition to the orientational and radial melting processes, isomerizations and complex size effects are seen to occur in a very similar way to atomic and molecular clusters. The results are discussed in terms of the energy landscape represented through disconnectivity graphs, with proper attention paid to the broken ergodicity problems in simulations. Clusters bound by 1/r(3) and e(-kappa r)/r forces, and heterogeneous clusters made of singly and doubly charged species, are also studied, as well as the evolution toward larger systems.