[CP2K-user] [CP2K:15575] GAPW: How does r_loc affect energies?

[Hayden Scheiber]

Thank you for the explanation, Matthias.


On Wednesday, June 16, 2021 at 1:16:38 AM UTC-7 Matthias Krack wrote:

> Hello Hayden
>
>  
>
> r_loc defines the exponent \alpha_C of the core charge distribution. Check 
> section 2.3 of this reference <https://doi.org/10.1039/B001167N> for 
> further details. While this parameter is part of the parameter set of the 
> GTH pseudopotentials (local part), it can be in principle arbitrarily 
> chosen for all-electron calculations, but for reasons of computational 
> efficiency and accuracy, r_loc should not be too small or too large. 0.5 
> turned out to be a reasonable choice, which should also work for At.
>
> The atomic regions for the hard part of GAPW are defined by the 
> HARD_EXP_RADIUS 
> <https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/KIND.html#HARD_EXP_RADIUS> 
> keyword key.
>
>  
>
> HTH
>
>  
>
> Matthias
>
>  
>
> *Von:* c... at googlegroups.com <c... at googlegroups.com> *Im Auftrag von *Hayden 
> Scheiber
> *Gesendet:* Dienstag, 15. Juni 2021 22:36
> *An:* cp2k <c... at googlegroups.com>
> *Betreff:* [CP2K:15575] GAPW: How does r_loc affect energies?
>
>  
>
> Hello,
>
>  
>
> I'm attempting a series of all-electron DFT calculations involving the At- 
> ion, but astatine is not defined in the ALL_POTENTIALS file. I added in my 
> own astatine section into my local ALL_POTENTIALS file as follows:
>
>  
>
> At ALLELECTRON ALL
>
>    12   29   30    14
>
>      r_loc    0
>
> #
>
>  
>
> I don't know what choice of r_loc to use (e.g. 0.5 is used for iodine). I 
> can't find any documentation on how r_loc values are chosen. I believe that 
> r_loc defines the border between the hard (local) and soft (interstitial) 
> parts of the GAPW calculation. Is this correct? I attempted a few test 
> calculations with varying values of r_loc on a non-periodic At atom, and 
> the resulting total energy varies a lot (10s of Hartrees). Why does the 
> energy vary so much with r_loc? How should I select my value of r_loc?
>
>  
>
> Attached is the CP2K input I'm using.
>
>  
>
>  
>
> Thanks,
>
>  
>
> Hayden Scheiber
>
>  
>
>  
>
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