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

Marcella Iannuzzi marci... at gmail.com
Thu Aug 8 12:45:43 UTC 2019

Dear Pierre,

the attached input for geometry optimisation seems to work fine. 
According to the resulting stress tensor, the given cell is too small in 
all directions and a cell_opt simulation should lead to a larger cell.
I did not run a cell_opt though. 


On Wednesday, August 7, 2019 at 5:05:56 PM UTC+2, Pierre-André Cazade wrote:
> 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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