[CP2K-user] [CP2K:11166] general normconserving UPF in CP2K

hut... at chem.uzh.ch hut... at chem.uzh.ch
Fri Jan 11 13:38:18 CET 2019


Hi Michiel

>
>I have run some tests on this topic and would just like to share my experience.
>
>I ran the pseudo-dojo 0.4 PBE Si pseudo potential combined with the the molopt GTH DZ basis set.
>
>It took me some time and reading the source code to find out how but eventually cp2k ran. I now use
>
>    POTENTIAL_FILE_NAME PD04-UPF-POTENTIALS (in the &DFT section) 
>
>and
>
>    &KIND Si
>      POTENTIAL UPF PD04-UPF-POTENTIALS
>      BASIS_SET DZVP-MOLOPT-SR-GTH
>    &END KIND
>

The POTENTIAL_FILE_NAME should not be necessary. What would you do if there are two different atoms?

>Comparing calculations with the same cutoff and relcutoff, only the psp is different, I observe the following
>
>1) I needed to turn of non linear core corrections to prevent cp2k to segfaut in the conversion step

This is probably a bug? I thought NLCC worked but I cannot find an example to proof it.

>
>2) It seems the gausian fit results in many more gausians than the typical GTH pseudo's
> - This however does not seem to deteriorate performace: calculate_rho_elec and integrate_v_rspace take more or less the same time per iteration for both psp's 

The internal format is similar but not exactly the same as the GTHs. Yes, there are much more Gaussians needed for the fit.
Performance is not a major concern, as CP2K calculates the PP integrals analytically and adds them to the core Hamiltonian
at the start of the calculation. During the SCF there is no overhead.

>3) I observe a somewhat improved convergence with cutoff and rel_cutoff, comparable to what I am used to when using this pseudo in abinit

The cutoff in CP2K is related to the density cutoff in abinit, usually 4x the input cutoff.
rel_cutoff is a CP2K internal accuracy setting for the integrations of Gaussians, there is no relation to any cutoff in abinit.

>4) The electronic convergence systematically takes more steps.
> - I assume this is caused by the use of basisfunctions not optimized for this pseudo (can someone confirm?)

This is not clear, more steps than in abinit? The number of steps depends on the optimizer. CP2K is rather good for insulators and using
the OT method. For metals and diagonalization methods you need to find the best setting, defaults are not very good.

>5) in the case of the UPF pseudo I see an additional  read_qs_kind in the timing report, I assume this is the part where the upf is read and fitted. I assume it >should be possible to do this fit once and safe the GTH format.

see above. The fit is not compatible with the GTH format, you cannot just print and reuse it.

Thanks for testing this feature.

best regards

Juerg


Any comment is welcome.

Please let me know if someone thinks I'm polluting this channel ;-)

thanks for reading,
Michiel

Op dinsdag 18 december 2018 09:29:20 UTC+1 schreef jgh:Hi 
 
there is minimal support for general normconserving pseudopotentials from UPF 
in CP2K. The potentials are internally fit to a Gaussian form, similar 
to the GTH pseudos. The accuracy of the fit has not been thoroughly 
tested. It should work for most variants (semi-local, non-local) forms, 
but again only minimal testing has been done. 
There are plans to implement a direct integration of the UPF pp  
sometime next year.  
Another problem will be the available basis sets. You will need 
to generate also those, or rely on the PBE-GTH optimized basis sets. 
 
best regards 
 
Juerg 
-------------------------------------------------------------- 
Juerg Hutter                         Phone : ++41 44 635 4491 
Institut für Chemie C                FAX   : ++41 44 635 6838 
Universität Zürich                   E-mail: hut... at chem.uzh.ch 
Winterthurerstrasse 190 
CH-8057 Zürich, Switzerland 
--------------------------------------------------------------- 
 
-----"'Michiel van Setten' via cp2k" <cp... at googlegroups.com> wrote: ----- 
To: "cp2k" <cp... at googlegroups.com> 
From: "'Michiel van Setten' via cp2k" <cp... at googlegroups.com> 
Date: 12/17/2018 11:40AM 
Subject: [CP2K:11053] general normconserving UPF in CP2K 
 
Dear community, 
 
I have seen some keywords concerning the use of UPF pseudo potentials in CP2K, I however did not manage to figure out if this means cp2k can use general normconserving UPF pseudopotentials.  
 
I would like to make some pseudopotentials with different amounts of valence electrons for some elements. Since I have some experience in generating ONVPSP pseudo potentials, for me the easiest would generate ONCVPSP's and use them in CP2K, either in upf format or, as a second option, via a conversion into HGH format.  
 
If any one has some experience, it would be very welcome, reasons why this would be a bad idea would be equally welcome ;-) 
 
many thanks, 
Michiel van Setten 
 
   
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