[gmx-users] Stochastic Dynamics nsttcouple

[Justin Lemkul]

On 11/6/19 10:40 AM, John Whittaker wrote:
> Hi all,
>
> Please correct me if this is the wrong list for this particular question.
>
> I have been messing around with the stochastic dynamics integrator in
> version 5.1 (yes, it's relatively ancient, but I am testing some things
> involving AdResS) and I can't wrap my head around something:
>
> In the src/gromacs/mdlib/update.cpp file, I cannot find a moment when the
> parameter "nsttcouple" is used in order to determine when the thermostat
> is applied. I'm not sure if this is a stupid question, but are the
> friction and noise applied at each step, regardless of the value of
> nsttcouple?
>
> I understand that tcoupl is ignored when the SD integrator is used, but
> does this mean that nsttcouple is ignored, too?

Yes. Formally, the SD integrator does not apply an explicit thermostat 
algorithm; velocities are updated based on the friction coefficient 
specified in the .mdp file. nsttcoupl is only relevant when tcoupl is 
active, which it is not when using SD.

-Justin

> I am by no means an expert in C++ so I could have easily misunderstood or
> missed something, but this question has been plaguing me for a couple
> days. Any help I can get to better understand this is much appreciated!
>
> Best,
>
> John
>
>
>
>

-- 
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Justin A. Lemkul, Ph.D.
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