**From:** Brian Radak (*brian.radak_at_gmail.com*)

**Date:** Tue Nov 06 2018 - 13:34:00 CST

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Technically Langevin dynamics should totally obscure physical diffusion -

the friction coefficient is meant to model effects that are already present

due to molecular collisions in the condensed phase. Values considerably

larger than 5 ps^-1 would be appropriate for implicit solvent simulations

where the model does not explicitly include these effects. That being said,

rather small values of the coefficient may lead to barely distinguishable

perturbations of the dynamics. See for example:

Effects of Temperature Control Algorithms on Transport Properties and

Kinetics in Molecular Dynamics Simulations

<https://pubs.acs.org/doi/10.1021/ct400109a>

Joseph E. Basconi and Michael R. Shirts

J. Chem. Theory Comput., *2013*, *9* (7), pp 2887–2899

HTH,

BKR

On Tue, Nov 6, 2018 at 12:32 PM Mani Kandan <manikandand5110_at_gmail.com>

wrote:

*> Dear all,
*

*> What are the important things to be considered while choosing
*

*> the Langevin dynamics coefficient value? I want to maintain the diffusion
*

*> coefficient of water as same in experimental conditions. Then what is the
*

*> appropriate value of Langevin dynamics coefficient value that I have to
*

*> choose?
*

*>
*

*> I found some researchers are using 5.0 1/ps value for
*

*> Langevin coefficient. Is these value enough to represent experimental
*

*> conditions? Kindly help me in this regard.
*

*>
*

*> MANIKANDAN D
*

*>
*

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