Editing Molecular dynamics (section)

=== Canonical ensemble (NVT) ===

In the [[canonical ensemble]], amount of substance (N), volume (V) and temperature (T) are conserved. It is also sometimes called constant temperature molecular dynamics (CTMD). In NVT, the energy of endothermic and exothermic processes is exchanged with a [[thermostat]].

A variety of thermostat algorithms are available to add and remove energy from the boundaries of an MD simulation in a more or less realistic way, approximating the [[canonical ensemble]]. Popular methods to control temperature include velocity rescaling, the [[Nosé–Hoover thermostat]], Nosé–Hoover chains, the [[Berendsen thermostat]], the [[Andersen thermostat]] and [[Langevin dynamics]]. The Berendsen thermostat might introduce the [[flying ice cube]] effect, which leads to unphysical translations and rotations of the simulated system.

It is not trivial to obtain a canonical ensemble distribution of conformations and velocities using these algorithms. How this depends on system size, thermostat choice, thermostat parameters, time step and integrator is the subject of many articles in the field.