7. Molecular Dynamics in other Ensembles

NVT, NVE, NPH, NPT, ...

In the basic MD setting the macroscopic observables $N,V,E,\vec{p}$ are held constant (where $\vec{p}$ is the total linear momentum.) This defines the so-called ``MD ensemble'' which can be shown to be thermodynamically equivalent to the other ensembles.

Other ensembles may be of advantage for specific problems: $NVT$ is useful for comparisons with theory and MC simulations; non-equilibrium simulations require a thermostat, thus $T=const$; phase transitions are best studied in an $NPT$ ensemble, etc.