[CP2K-user] [CP2K:12052] Re: Cell Optimization does not work in QM

[Pierre Cazade]

Hello Dirk,

Thank you for the files. I will have a careful look at them and give 
them a try. I will test the MP2 method on my small crystal and see if it 
gives the correct optimization.

What bothers me with my systems is that it is not only the crystal which 
is expending but also the inter atomic distance, by which I mean, the 
distance between two atoms that are part of the same molecule. For 
example, the N-H bond length of the -NH3+ group of my glycine molecule 
increases from 0.98 A to 1.4 A, at the point where I stopped the 
calculation. It feels like there is a problem with the input coordinates 
or that they are understood by cp2k as been in Bohr whereas they are in 
Angstrom.

Thanks again,
Pierre

On 08/08/2019 07:01, Dr. Dirk Buddensiek wrote:
> Good morning Pierre,
> please find enclosed an example which at least worked for computation 
> of the unit cell of p-Dimethylaminothiopivalophenone. Unfortunately 
> the Online-Manual of CP2K is not self-explanatory. But there is a lot 
> of material (Tutorials, Excercises from summer Schools etc.) available 
> which might help.
> Hope you succeed with the input file. Don´t worry. I had some similar 
> experience in the beginning.
> Kind regards
> Dirk
> PS: In really difficult cases I guess Juerg Hutter and / or Marcella 
> Ianuzzi can help.
>
> 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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-- 
Dr Pierre Cazade, PhD
AD3-023, Bernal Institute,
University of Limerick,
Plassey Park Road,
Castletroy, co. Limerick,
Ireland

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