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

Pierre-André Cazade pierre.a... at gmail.com
Wed Aug 7 15:05:56 UTC 2019


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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