CHARMM (Chemistry at HARvard Macromolecular Mechanics) is a program for macromolecular dynamics and mechanics.
CHARMM can perform molecular dynamics in many different ensembles (e.g., NVE, NVT, NPT) using state-of-the-art algorithms for timestepping, long range force calculation (including Ewald and PME methods) and periodic images.
Some selected features:
There is a licensing restriction. CHARMM is made available to academic users as source code, plus documentation and test input scripts, through Martin Karplus' group at Harvard University.