Langevin molecular dynamics with quantum forces: Application to silicon clusters.

Abstract

We have implemented a dynamical stochastic scheme to determine from first principles the structure of complex low-symmetry atomic systems such as surfaces and clusters. The method is based on Langevin molecular dynamics and quantum-mechanical interactions derived from ab initio pseudopotential calculations. No fictitious electron dynamics is employed, and insulating as well as metallic or charged systems can be handled in a straightforward manner. We apply this method together with the simulated annealing strategy to small neutral and charged silicon clusters, and show that the ground-state structures can be efficiently obtained with this approach. We also exploit this scheme to perform first-principles isothermal molecular-dynamics simulations, and examine the adsorption of a Si atom on a cluster.