Re: [AMBER] Effect of different gamma_ln values

From: Adrian Roitberg <>
Date: Mon, 1 Mar 2021 18:42:50 -0500

I do not think that is completely correct.

The effect clearly depends on the system, solvent, etc.

For example for a very small system in vaccum or implicit solvent, then
you are reasonably correct.

For a large system, the dominant friction could easily be the internal
friction due to the presence of close contacts. In explicit solvent, the
friction is completely dominated by the solvent friction, and there is
no real difference between using a langevin gamma_ln or 0.1, 1, 2, or 10.


On 3/1/21 3:29 PM, Liao wrote:
> [External Email]
> Dear Amber Community,
> If I understood it correctly, the gamma_ln value for the Langevin thermostat affects the conformation search speed, that the smaller the value the faster the search, and vice versa.
> But what about NVE and NPE ensembles that don’t have thermostats? Or if using other types of thermostats? What will the conformation search speed be equivalent to in those scenarios, will it be more like gamma_ln=0.01 (or some other small number)?
> Thanks there.
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Dr. Adrian E. Roitberg
V.T. and Louise Jackson Professor in Chemistry
Department of Chemistry
University of Florida
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Received on Mon Mar 01 2021 - 16:00:02 PST
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