[CP2K-user] [CP2K:19647] Finite temperature optimization

[Simone Ritarossi]

Thank you very much for your reply. However, I think I don't quite 
understand: in CP2K I can do a CELL_OPT and get the relaxed system at 0K; 
can I instead get the relaxed cell at a temperature of 300K? 

I could extract from the trajectory N configurations of the system at 300K 
and for each of these do a CELL_OPT, evaluating the volume behaviour. Does 
this make sense?
 
Thanks again for your time

Simone 

Il giorno lunedì 11 dicembre 2023 alle 17:44:26 UTC+1 Thomas Kühne ha 
scritto:

> Dear Simone Ritarossi, 
>
> just 2 comments from my side. 
> (i) When using CELL_OPT/TYPE MD, a MD simulation is conducted to obtain 
> the ensemble averaged stress tensor to conduct 
> your cell optimization. This is not only excessively expensive (in your 
> case a 10000 step AIMD calculation is performed for each 
> cell optimization step!), but in my experience is also not effective due 
> to the inherent fluctuations in the stress tensor, in particular 
> when using this in conjunction with a quasi-Newton optimizer such as BFGS 
> that tolerates noise very poorly. 
> (ii) In the comment of your input file you write "Performs a geometry and 
> cell optimization at the same time. The stress tensor is 
> computed at every step“. If this is what you want to do simply use TYPE 
> DIRECT_CELL_OPT instead. 
>
> Greetings, 
> Thomas Kühne
>
> Am 11.12.2023 um 10:17 schrieb Simone Ritarossi <sim.ri... at gmail.com>:
>
> Dear users,
>
> I have a problem with the use of CELL_OPT at temperatures other than 0K. 
> Following CP2K's guide (I could not find any discussions on the subject on 
> the web), I understood that I have to 1) set the RUN_TYPE CELL_OPT, 2) 
> define TYPE MD in the CELL_OPT section and 3) define an MD section.  In the 
> guide it says " * Two possible schemes are available: (1) Zero 
> temperature optimization; (2) Finite temperature optimization*  ". 
> However, I do not get the optimization. .
> I attach here the input and output files. I cannot understand the error in 
> the output (I cannot find anything similar on the web): the abort message 
> is " CPASSERT failed -  motion/gopt_f77_methods.F:307"
>
>
> Thank you for your time!
>
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> .
> <PCH_GST_TiTe2_CELL_OPT_MD.out><PCH_GST_TiTe2_CELL_OPT_MD-MD-1.out>
> <PCH_GST_TiTe2_CELL_OPT_MD.inp><PCH_GST_TiTe2_CELL_OPT_MD-MD-0.out>
> <job.err>
>
>
>

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