[CP2K-user] [CP2K:15029] Gentle Heating

[Marcella Iannuzzi]

Dear Lenard, 

Heating the system by constantly rescaling the velocity generates a 
dynamics that does not correspond to any meaningful thermodynamic ensemble.
For sure, to set up a thermostat while forcing the temperature to change is 
not a good idea.
If you want to use the ANNEALING in cp2k just set NVE, obviously the energy 
is not going to be conserved.
Activating the annealing, at each step the actual temperature is multiplied 
by the scaling factor and the velocities are rescaled accordingly.

Probably a better way to bring the system from a lower to a higher 
temperature would be to run a set of NVT simulations at increasing 
temperature, say 150K, 300K, ...800K
Each simulation should be several ps long, such that the system has the 
time to sort of equilibrate at each temperature before ramping up.

best
Marcella


On Monday, March 29, 2021 at 4:19:17 PM UTC+2 jos... at gmail.com wrote:

> There is no way to do 800K over 2 ps.
>
> On Mon, Mar 29, 2021, 15:03 ASSIDUO Network <len... at gmail.com> wrote:
>
>> Good day, I trust you are doing well.
>>
>> I'm in the process of getting my hands dirty with AIMD using CP2K. I am 
>> familiar with MD simulations from AMBER, but not quite yet CP2K.
>>
>> I would like set up a gentle heating in my AIMD simulation, gently 
>> heating the box up from 0 K to 800 K. I have read on this group that 
>> annealing should be used for this, but my issues here are the following:
>> - The heating phase has the volume and number of molecules constant, but 
>> allows the energy, the temperature and the pressure to change. None of the 
>> ensembles seem to fit this. So, I decided to go with NVT since that is what 
>> I have used with the heating simulation with AMBER (many tutorials 
>> available on it), but there you could specify the initial and reference 
>> temperature.
>> - How do I properly use annealing to heat the temperature up from 0 K to 
>> 800 K over 2 ps? Annealing just scales the velocities of the particles, so 
>> I'm not sure how to best choose this scaling factor.
>> - How do I print the temperature throughout the AIMD run?
>>
>> I have included my input file. I would appreciate if you could go through 
>> the &MOTION section and tell me if it all makes sense.
>>
>> Kind regards,
>> Lenard
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "cp2k" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to cp... at googlegroups.com.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/cp2k/e2da3b1a-39d8-45aa-912f-531eb540f12en%40googlegroups.com 
>> <https://groups.google.com/d/msgid/cp2k/e2da3b1a-39d8-45aa-912f-531eb540f12en%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20210329/301c37c2/attachment.htm>