NWChem: Exploiting parallelism in molecular simulations

NWChem is the software package for computational chemistry on massively parallel computing systems developed by the High Performance Computational Chemistry group for the Environmental Molecular Sciences Laboratory. The software provides a variety of modules for quantum mechanical and classical mechanical simulation. This article describes the design of the molecular dynamics simulation module, which is based on a domain decomposition, and provides implementation details on the data and communication structure and how the code deals with the complexity of atom redistribution and load balancing.