[CP2K:3415] Thermostat regions in MD

[Teodoro Laino]

This is not possible. The region section is only specifying an ensemble of atoms in which the temperature is kept under control.
But the thermostat (type/temperature/coupling) has to be the same for all the regions (this is the reason why it cannot be repeated).

Teo

On Aug 9, 2011, at 5:35 AM, Philippe C. A. wrote:

> Hi all,
> 
> I have a simple MM-only system of a couple hundred atoms of types A
> and B. What I would like to do: Attach a Nose-Hoover or Gaussian
> Isokinetic thermostat to all atoms of type B, but not A, i.e.
> particles B move according to the Nose-Hoover (or GIK) equations of
> motion, whereas particles A have no thermostat and simply move
> according to Newtonian dynamics.
> 
> From the input manual I had some hope that this would be possible
> using the "thermal_region" and "define_region" subsections and from my
> interpretation of it I created an input structure like this and
> thought it would do what I want:
> 
> &MOTION
> &MD
>  ENSEMBLE NVT
>  TEMPERATURE [K] 500.0
>  &THERMOSTAT
>   TYPE NOSE
>   REGION DEFINED
>   &DEFINE_REGION
>    LIST 1 2 3 [...] 250   # My system has 250 particles A and 250
> particles B
>   &END DEFINE_REGION
>   &NOSE
>    LENGTH 1
>    TIMECON [fs] 1.0e-2
>   &END NOSE
>  &END THERMOSTAT
>  TIMESTEP [fs] 1.0 fs
>  STEPS 20
> &END MD
> &END MOTION
> 
> The result however was disaster - all NaN positions/forces and CP2K
> complains that "no thermostat is attached to particles 251-500" (and
> if I do try to attach one to them, it complains that the thermostat
> input section cannot be repeated....).
> With the GIK thermostat - which in CP2K is not treated as a thermostat
> but as an ensemble - I tried the "motion%md%thermal_region" subsection
> in the hope that it would only treat the listed atoms within the
> ISOKIN ensemble and the non-listed atoms with simply Newtonian EOM,
> but that does not happen.
> 
> Could somebody clarify the intended use of the "region" keywords and
> how they work, and if it is possible to achieve what I described above
> with the current CP2K functionality with Nose and Gaussian
> thermostats?
> 
> Many thanks,
> Philippe
> 
> PS: I am using the "release" branch of CP2K.
> 
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