[gmx-users] The time for the temperature and pressure coupling

[Michael Shirts]

Ah, now perhaps I see that I misread the question - it could have been
phrased more clearly.  If Erik understood it correctly, then the
answer to the question is: It depends on the integrator.  The
simulation is not constrained to a particular temperature or pressure
- rather, the dynamics are modified such that the ensemble is
consistent with the external temperature and pressure are specified.
Exactly where in the integration routine the dynamics are modified
depends on the method used.  See the manual for more of the details!

On Thu, Feb 7, 2013 at 3:59 AM, Erik Marklund <erikm at xray.bmc.uu.se> wrote:
> Hi,
>
> Perhaps a side point: Temperature and pressure can not be seen as
> constraints to the system at any given instant in the sense that e.g. the
> instantaneous kinetic energy perfectly match the temperature at every time
> step just because you have a thermostat. Time and ensemble averages will,
> however, reflect the temperature and pressure coupling.
>
> Erik
>
>
> On Feb 6, 2013, at 11:28 PM, Bao Kai wrote:
>
>> Dear Gromacs Team,
>>
>> I have a small question related to the scheme of the MD in Gromacs.
>>
>> When are the temperature and pressure constrains are enforced, before
>> the update of the velocity and position or after?
>>
>> Thank you very much.
>>
>> Best Regards,
>> Kai
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