Molecular dynamics (MD) is the simulation of the movement of individual atoms in a system. Such a simulation typically fixes a number of thermodynamical variables such as number of particles (N), volume (V), temperature (T), energy (E), or pressure (P). A simulation fixing, e.g., the three former variables is referred to as "NVT" MD.
The Atomic Simulation Environment implements several kinds of MD for use with either classical force fields or ab-initio simulations with the possibility of interfacing different electronic structure codes.
i-PI is a molecular dynamics code in Python designed for ab-initio MD with the possibility of interfacing different electronic structure codes.