Hybrid molecular dynamics: an approach to low density simulations

A new molecular dynamics technique is described which addresses the special problems intrinsic to low density simulations, particularly fluids in the gas phase. This technique incorporates aspects of both the conventional hard spheres and continouos potential molecular dynamics algorithms. The difficulties inherent in low density simulations are discussed and the synthesis of existing molecular dynamics techniques into a new, hybrid algorithm is described in detail, including optimization and vectorization modifications. Finally, benchmarks for the new code are reported which show a speedup of up to a factor of 7 over a traditional molecular dynamics program.