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[verstraete@pcpm.ucl.ac.be]

Hello Kristopher. 

You can believe the psp6 info file: the value of fchrg has no meaning. If 
it's > 0 the nlcc is used. If fchrg = 0, nlcc isn't used. Period. I always 
use fchrg = 1, but you may prefer 99999.

If it still doesn't work, I'll send you a copy of mine (made with the
default file for Li by Martin Fuchs).

Matthieu

On Wed, 20 Nov 2002, Kristopher Andersen wrote:

> In trying to generate a pseudopotential using the PBE GGA functional
> for Lithium (not available on the web site) with the Fritz-Harber
> Institute code, I'm not sure how to choose the value of fchrg, the
> amplititude of the core charge.
> 
> The help file Infos/Psp_infos/psp6.info says the following, but offers
> no advice on how to choose fchrg. (It goes into some depth on how to
> choose rchrg.)
> 
>  fchrg: amplitude of core charge (if =0 non core-correction performed,
>         if >0 core-correction is applied). The specific value of fchrg
>         has no physical meaning in fhi98pp scheme of core correction.
> 
> In the .cpi output file, there are values of the core charge and it's
> derivatives on the radial mesh. Is it appropriate to set fchrg equal
> to the value of the core charge at the core cutoff radius (rchrg) one
> would choose for the model core?
> 
> I was hoping that looking at the fhi pseudopotential for Na, which is
> available on the web site, might shed some light on this, but
> apparently that pseudopotential doesn't include nonlinear XC core
> corrections. I was under the impression that for sodium these would be
> needed?
> 
> Any help or advice is appreciated.
> 
> 

-- 
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Matthieu Verstraete               mailto:verstraete@pcpm.ucl.ac.be 
PCPM, Boltzmann, pl. Croix du Sud, 1            tel: 010/ 47 86 81
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