Langevin dynamics
is turned
on by a nonzero FBETA (friction) array, a
nonzero ILBFrq parameter,
and an appropriate choice of RBUF. Langevin
dynamics represents a coupling of the system to a heatbath
and thus provides a means to control and maintain temperatures.
A harmonic energy term
can be used to restrain the Langevin particles and provide
a rough approximation of a potential of mean force.