[CP2K:1748] Re: different regions with different temperature in MD

Teodoro Laino teodor... at gmail.com
Mon Feb 2 15:37:42 UTC 2009

Hi Jun

then you don't need at all the different thermostatting region at 
different temperatures.
You can specify velocities in the section &VELOCITIES in &SUBSYS.
These velocities act like restart quantities.

You can (with a small external program) determine the velocities of the 
hotter atoms through a Boltzman distribution at temperature T1, and the 
velocities of the other atoms at temperature T2 (T1>T2).
You can then input these quantities in the &VELOCITIES section and run 
your MD.

Of course you may consider about running an NVE ensemble instead of the 
NVT (which you were mentioning in your previous message). NVE  makes 
more sense to me in order to inspect heat transfer (but of course more 
expert people can comment on this point).

Jun Cheng wrote:
> Thanks a lot for rapid reply, Teo.
> What I am trying to simulate is that a few atoms or molecules in an 
> equilibrated system are excited to higher vibrational levels (e.g. due 
> to photo adsorption), and see how the system evolves afterwards. I am 
> thinking of assigning the excited species an high temperature 
> initially to mimic the situation of excitation by photo adsorption, 
> and then seeing how the system reacts. So, it is not necessary to keep 
> the excited species at the high temperature during MD simulations. 
> Please let me know what do you think. Thanks.
> Jun
> On Mon, Feb 2, 2009 at 3:09 PM, Teodoro Laino <teodor... at gmail.com 
> <mailto:teodor... at gmail.com>> wrote:
>     Dear Jun,
>     it is possible to define different thermostatting regions but all of
>     them have the same temperature.
>     It would not work (most of the time) having different regions at
>     different temperatures unless the regions
>     are not fully adiabatic. In fact, different regions at different
>     temperatures ( in case of energy flow between
>     the different regions) would never thermalize to the temperature you
>     asked for..
>     Cheers
>     Teo
>     Jun wrote:
>     > Dear all,
>     >
>     > Is it possible to define different regions with different
>     temperatures
>     > in a MD simulation using cp2k? If yes, how to do that?
>     > Many thanks in advance.
>     >
>     > Jun
>     > >
>     >
> >

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