[CP2K-user] Cell Optimization does not work in QM

[Dr. Dirk Buddensiek]

Dear Pierre,
at first glance the CUTOFF and RELCUTOFF seem to be a lttle bit unbalanced. 
Maybe it would help to take a look in the tutorial hpw to get optimised 
cuttof values. https://www.cp2k.org/howto:converging_cutoff

Am Mittwoch, 7. August 2019 17:05:56 UTC+2 schrieb Pierre-André Cazade:
>
> Hello,
>
> I am rather new to CP2K though I am experienced with molecular modelling 
> both quantum and classical, and with a wide range of software. It is quite 
> frustrating that it seems impossible to get CP2K to perform a simple 
> CELL_OPT of a beta glycine crystal (20 atoms, monoclinic) with PBE. Such a 
> calculation works fine with VASP, so I am quite surprised the same 
> calculation goes astray with CP2K. Basically, the B unit cell vector 
> increases drastically up to absurd values. Needless to say, this is a test 
> system as I wish to use CP2K for its linear scaling DFT to model protein 
> crystals. I have tried to play with CUTOFF and REL_CUTOFF in the MGRID 
> section up to 1400 and 80 respectively. I also tried GPW and GAPW methods, 
> all electrons or GTH pseudo. Nothing works. Please, if anyone could have a 
> look at the attached input file "cell_opt_qm.inp" and point what's wrong in 
> it, I would be grateful.
>
> Furthermore, I have tried LS approach with DFTB on a 5x5x5 crystal of beta 
> glycine and do not have much more success. First, the pressure in the 
> crystal is insanely high and will lead again to a 20 folds increase of the 
> lattice vectors (with CG). Then, with LBFGS method, the system stops after 
> 3 to 4 cycles with a message telling LBFGS convergence criteria were 
> reached, whereas the system is clearly not. Again, I would be grateful if 
> anyone could tell me what's wrong with my system ("cell_opt2_qm.inp" with 
> "betacry.pdb" for the coordinates). Ideally, my goal would be to be able to 
> run large complex systems with the LS approach and with any DFT/DFTB method.
>
> Thank you in advance for your help.
>
> Regards,
> Pierre
>
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