[CP2K-user] Co(111) Geometry optimization with kpoints

[fa...@gmail.com]

Hi Manuel,

According to the manuel the wavelet solver supports *"slab-boundary 
conditions (but only PERIODIC XZ)." *You are correct to change the k-point 
grid accordingly.

To avoid the warning you mentioned need to increase the cell length in the 
y-direction.

To reduce the number of scf iterations you can optimize the &MIXING 
section, in particular NBUFFER 
<https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/SCF/MIXING.html#NBUFFER> 
and ALPHA 
<https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/SCF/MIXING.html#ALPHA>. 
If you don't expect the multiplicity to change during MD you can disable 
RELAX_MULTIPLICITY to further improve scf convergence. And lastly you can 
tune the EXTRAPOLATION. 
<https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/QS.html#EXTRAPOLATION>

Cheers,
Fabian
On Tuesday, 19 January 2021 at 14:14:42 UTC+1 Manuel Corral wrote:

> Dear Fabian,
>
> Thank you very much for the commented file. It works, which it is already 
> a huge improvement, though it may take about 75 electronic iterations for 
> each ionic step, which may render a MD calculation too expensive. I wonder 
> if there is anything that could be done to speed it up.
>
> By the way, why do  you need to rotate the cell for the Wavelet Poisson 
> solver ? Based on this rotation, I would have thought of changing the 
> Monkhorst Pack set of k-points from 7x7x1 to 7x1x7, which you didn't and, 
> when I tried it, it did not work properly:
>
>  *** WARNING in pw/ps_wavelet_methods.F:236 :: Density non-zero on the ***
>  *** edges of the unit cell: wrong results in WAVELET solver.
>
> Thanks again.
>
> Regards,
> Manuel
>
> Le lundi 18 janvier 2021 à 18:03:26 UTC+1, fa... at gmail.com a écrit :
>
>> Dear Manuel,
>>
>> I changed a couple of things in the input and it's converging now 
>> (attached below). The changes include:
>> To use the WAVELET poisson solver I rotated the slab such that B is the 
>> surface vector. 
>> I also decreased RELAX_MULTIPLICITY because large values hinder scf 
>> onvergence. Maybe you need to test various initial guesses (see here: 
>> https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/SUBSYS/KIND/BS.html) 
>> to find the minimal energy configuration.
>> I increased the ELECTRONIC_TEMPERATURE in the &SEMEAR section. 300 K 
>> corresponds to just 0.02 eV in VASP which is very little.
>>
>> Cheers,
>> Fabian
>>
>> On Monday, 18 January 2021 at 14:53:36 UTC+1 Manuel Corral wrote:
>>
>>> Dear Colleagues,
>>>
>>> I have been trying to run a geometry optimization for with a Co(111) 
>>> 4-layer slab model without success. 
>>>
>>> I set up my initial input file according my previous experience with 
>>> another software (VASP) and then changed different calculation settings: 
>>> number of additional MOS (10, 30, 100), electronic temperature of the 
>>> smearing (300 K, 500 K), decreasing the cell in the vacuum direction, 
>>> changing the number of kpoints (gamma point with an increased cell), the 
>>> Poisson solver (analytical vs non analytical), the diagonalization 
>>> algorithm, settings in the mixing algorithm ... nothing worked. The SCF 
>>> cycle never converges.
>>>
>>> I would very much appreciate if you could give some advice or feedback 
>>> on my input files (enclosed).
>>>
>>> Thank you in advance for your help.
>>>
>>> Kind regards,
>>> Manuel Corral
>>>
>>>
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