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Next: Finite Difference Approximation Up: Temperature Control Previous: Langevin Dynamics

Temperature Coupling

This option is turned on by TCOUpling. This method was described by Berendsen et al. (1984). It is essentially a Langevin-type method with zero random forces and a scaled friction coefficient. The friction coefficient is computed by the program from the equation
\begin{displaymath} b_i=b_i^I (T_o/T -1) \end{displaymath} (11.7)

where $b_i^I$ is given by the FBETa atom property. Note that FBETa is by default zero; i.e., FBETa has to be specified in order to use TCOUpling. The target temperature $T_o$ is specified by the TBATh parameter. $T=\sum_i m_i {dx_i \over dt}^2 / ( {n_{deg} k_B} ) $ is the temperature of the system at the particular step where $n_{deg}$ is the number of degrees of freedom of the system. Thus, a positive fricition coefficient is applied if the system is too hot, a negative friction coefficient is applied if the system is too cold, and no friction is applied if $T$ matches $T_o$.


Xplor-NIH 2024-09-13