[CP2K:5115] Re: Equipartition and calculation of vibrational, rotational and translational Temperatures

[Rasoul Nasiri]

Hello Matt,

Many thanks.

I think even using NVE, one will be dealt with some errors in
non-equilibrium situations. Could anybody please comment on it?

Probably the reason is related to <mv2> = KBT in vibrational modes.

Best,
Rasoul


On Thu, Mar 27, 2014 at 7:23 PM, Matt W <MattWa... at gmail.com> wrote:

> Hi, interesting question, and I'd hope of interest to a few.
>
> I can't give a proper answer, but I think, in general, if you are not in
> equilibrium, equipartition is going to break - waving hands:
>
> (i) you can't define your modes properly.
> (ii) Also, most (all?, maybe some Langevin types recently implemented
> might escape this) thermostats only work at equilibrium too, so you'd be
> running NVE or similar where temperature isn't defined properly for a small
> cluster.
>
> I guess there are tricks for steady-state thermostatted non-equilibrium
> processes, but that is well beyond anything I know about.
>
> Matt
>
>
> On Thursday, March 27, 2014 10:16:07 AM UTC, Rasoul wrote:
>>
>> Dear All,
>>
>> Apologize if my question seems to be irrelevant for CP2K users.
>>
>> I'm trying to do a non-equilibrium MD simulation using CP2K in which one
>> molecule attacking the nano-droplet.
>>
>> My question is whether the equipartition of kinetic energy is satisfied
>> in the code for vibrational, rotational and translational modes at high
>> temperatures and non-equilibrium situations?
>> Having said this if <mv2> = KBT works properly for estimation of
>> temperature in the vibrational modes even using small time steps?
>>
>> Many thanks,
>>
>> Best,
>> Rasoul
>>
>>
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