[CP2K-user] [CP2K:10927] GAPW convergence for Cu and Ni

[Maxime Van den Bossche]

Dear Juerg,
Thanks a lot for your feedback -- with this, I will continue to use GAPW, 
exploring also the influence of EPSISO and EPSFIT, and checking the 
PW cutoff convergence when decreasing HARD_EXP_RADIUS.
Best,
Maxime



Op maandag 12 november 2018 03:20:32 UTC-5 schreef jgh:
>
> Hi 
>
> there are a few parameters that determine the numerical accuracy 
> of a GAPW calculation. We tried to pick good default values for 
> them, but it is well possible that for certain elements/basis set 
> combinations they do not work. 
> HARD_EXP_RADIUS sets the GAPW atomic sphere radius. The smaller 
> this value the higher the PW cutoff you will need. It shifts 
> the border between the soft and hard part of the basis set. 
> The same is also true for EPSFIT. This parameter sets the accuracy 
> of the fitting of the different densities at the GAPW sphere radius. 
> For heavy elements EPSISO can also be of importance (determines which 
> basis functions are completely within the GAPW sphere). 
>
> Usually, one can see the sensitivity of a calculation by changing these 
> parameters and then search for stable values. 
>
> best 
>
> Juerg Hutter 
> -------------------------------------------------------------- 
> 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 
> <javascript:> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
>
> -----cp... at googlegroups.com <javascript:> wrote: ----- 
> To: "cp2k" <cp... at googlegroups.com <javascript:>> 
> From: "Maxime Van den Bossche" 
> Sent by: cp... at googlegroups.com <javascript:> 
> Date: 11/10/2018 04:51PM 
> Subject: [CP2K:10927] GAPW convergence for Cu and Ni 
>
> Dear all, 
>
> I would like to use the GAPW method in CP2K to study 
> (late) transition metal clusters, as it would offer 
> quite an increase in speed compared to GPW (because 
> GAPW requires less high plane-wave cutoffs for dealing 
> with such "harder" pseudopotentials). 
>
> I had no problems performing GAPW runs for fifth- and 
> sixth-row elements (Pd, Ag, Pt, Au), but for the 
> fourth-row ones (Ni, Cu), I ran into severe SCF 
> convergence problems (strongly oscillatory behaviour). 
>
> I managed to create a minimal example, involving just 
> the Cu dimer, where this behaviour is also present 
> (see attached input and output files). In this particular 
> case, the SCF does converge when using the DIRECT_P_MIXING 
> mixing scheme, but this solution is not applicable to 
> my original problem, where I need e.g. Broyden mixing. 
>
> I then found that lowering the HARD_EXP_RADIUS parameter 
> to 1.2 Bohr radii or below (compared to the default value 
> of 1.512) makes the SCF cycle converge without problems. 
> I realize that the GAPW mode is still a bit more "experimental" 
> compared to GPW, so I'm fine with having to tinker with 
> such parameters, but I wanted to check with you: 
>
> Does it indeed make sense to you that the default value for 
> HARD_EXP_RADIUS is not appropriate here? Would this e.g. 
> be related to the shorter 3d-orbital radius for Cu compared to 
> Ag-4d and Au-5d? 
>
> Best regards, 
> Maxime 
>   
>   -- 
>  You received this message because you are subscribed to the Google Groups 
> "cp2k" group. 
>  To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+... at googlegroups.com <javascript:>. 
>  To post to this group, send email to cp... at googlegroups.com <javascript:>. 
>
>  Visit this group at https://groups.google.com/group/cp2k. 
>  For more options, visit https://groups.google.com/d/optout. 
>   
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20181112/7ee59c20/attachment.htm>