[CP2K:5392] How can I get the temperature converged in MD calculation (NVT) for system having H atoms?

[Ari Paavo Seitsonen]

Dear Jingyun Ye,

  If you start from a more or less optimised structure about half of the
initial kinetic energy first gets converted into an increase of potential
energy, and the thermostat is a bit slower: Your time constant now is 100
fs, but this does not mean that ionic temperature would reach this
temperature within the time constant (small value means faster
equlibration, at least in principle; if you use a value that does not
couple to the system - too small for example - then there will not occur
heat transfer). Rather it is a "characteristic frequency". If one needs to
equilibrate the initial part faster, one can try with the CSVR thermostat
and a smaller time constant, and later either increase the time constant or
then shift to the Nosé-Hoover thermostat chain.

  By the way, 0.1 fs is quite small a time step - do you need such a small
value? Well, it should certainly be a safe choice for any kind of system.

    Greetings,

       apsi

2014-06-11 22:15 GMT+02:00 Jingyun Ye <jingyu... at gmail.com>:

> Hi, all
>
> I am running a MD calculation for searching the most stable structure at
> room temperature. But the temperature goes from 300K to 150K after 1000
> steps and the energy goes up. My question is how can I get the temperature
> converged? Is there any thing wrong in my input? What is the reasonable
> TIMESTEP for the system having H atoms in it? Small TIMECON and big
> TIMECON, which one is more efficient for heat transfer?
>
> I included the input and results.
>
> Thanks very much.
> &MOTION
>  &MD
>   ENSEMBLE NVT
>   STEPS 10000
>   TIMESTEP 0.1
>   TEMPERATURE 300
>   &THERMOSTAT
>    TYPE NOSE
>     &NOSE
>      TIMECON 100
>     &END NOSE
>   &END THERMOSTAT
>  &END MD
> &END MOTION
>
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-- 
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  Ari Paavo Seitsonen / Ari.P.S... at iki.fi / http://www.iki.fi/~apsi/
  Institut für Chemie der Universität Zürich
  Tel: +41 44 63 55 44 97  /  Mobile: +41 79 71 90 935
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