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Simple Langevin Dynamics

  X-PLOR provides the possibility of carrying out Langevin dynamics. The simple Langevin equation has the form

where the random force is derived from a Gaussian distribution with the properties

where is Boltzmann's constant and is the temperature specified by TBATh. For Langevin heatbath applications, the total energy can be augmented by a harmonic energy term for all atoms with a nonzero friction coefficient . The setup of the harmonic energy is described in Section 7.1. The friction coefficient is defined by assigning the FBETa atom property (see Section 2.16). Langevin dynamics is used for all atoms that have nonzero friction coefficients and that are outside a sphere with radius RBUF (default 0) around the origin ORIGIn. This check is carried out periodically (ILBFrq parameter). By default the atom property FBETa is zero; i.e., all atoms are treated as normal particles.

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