[CP2K-user] [CP2K:12063] Re: Cell Optimization does not work in QM

Pierre-André Cazade pierre.a... at gmail.com
Thu Aug 8 14:30:50 UTC 2019

Dear Marcella,

Thank you for the input file. I will give it a try right away and see how things goes.


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From: cp... at googlegroups.com on behalf of Marcella Iannuzzi <marci... at gmail.com>
Sent: Thursday, August 8, 2019 1:45 p.m.
To: cp2k
Subject: [CP2K:12063] Re: Cell Optimization does not work in QM

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:

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.


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