Including inner shell electrons in GPW calculations

[Marcella Iannuzzi]

Hi Rustam, 

the Mg basis set has functions with rather large exponent, this requires 
high cutoff with GPW. 
The alternative is to use GAPW, with the same PP and BS, then the hard part 
of the density is not collocated on the regular grids and a lower cutoff 
can be used. 
However, GAPW has some overheads with respect to GPW. 
Possibly another solution are the NLCC pseudo potentials, but you should 
check and test what is available. 

cheers
Marcella

On Friday, June 24, 2016 at 7:47:04 PM UTC+2, Rustam wrote:
>
> Hi guys,
>
> I need to include inner-shell electrons of Mg into my GPW calculations. 
> That is the total number of electrons on magnesium must be 10, not just 2 
> valence 3s electrons.
>
> This can be readily achieved using by using the following pseudopotential
>
> &KIND Mg
>
>   BASIS_SET DZVP-GTH
>
>   POTENTIAL GTH-BLYP # 2s2 2p6 3s2 configuration
>
> &END
>
>
> instead of typical
>
>
> &KIND Mg
>
>   BASIS_SET DZVP-GTH
>
>   POTENTIAL GTH-BLYP-q2 # 3s2 
>
> &END
>
> I figured (by trial and error) that including inner electrons requires 
> significantly higher CUTOFF setting. The attached plot shows energy 
> dependence on the cell size of MgH2.
>
> A. 2-electron calculations are fine with 1000 Ry cutoff
> b. 10-electron calculations produce awful results unless the cutoff is 
> above 8000 Ry.
>
> QUESTION: Is it really necessary to use such a high cutoff to get smooth 
> curves? Or are there any other settings one can tweak to get accurate 
> results with lower (i.e. cheaper) cutoff?
>
> Thanks!
> Rustam
>
>
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