A NEW ALGORITHM FOR MOLECULAR-DYNAMICS SIMULATIONS IN THE GRAND-CANONICAL ENSEMBLE

We present an algorithm for implementing molecular dynamics simulation s in the grand canonical ensemble that takes advantage of parallelism. The algorithm is an extension of the one presented recently for perfo rming Monte Carlo simulations in the same ensemble. In contrast to mos t commonly used algorithms for open systems, instead of physically add ing or deleting molecules to generate concentration fluctuations, para llel sets of trajectories are generated using molecular dynamics simul ations in the canonical ensemble, corresponding to various composition s. Appropriate combinations of chains of configurations are selected a ccording to the prescription of the grand canonical probability distri bution. The method is illustrated for a test case of the isotopic Lenn ard-Jones mixture. We compare the thermodynamic properties obtained wi th this parallel method to those obtained from the Adams algorithm for performing Monte Carlo simulations in the same ensemble, observing a faster convergence to equilibrium and smaller errors with our method. Comparisons with the parallel Monte Carlo algorithm are also made.