GROMACS

GROMACS (GROningen MAchine for Chemical Simulations) is a molecular dynamics simulation package originally developed in the University of Groningen.

It is primarily designed for biochemical molecules like proteins, lipids and nucleic acids that have a lot of complicated bonded interactions, but since GROMACS is extremely fast at calculating the nonbonded interactions (that usually dominate simulations) many groups are also using it for research on non-biological systems, e.g. polymers.