[Pw_forum] ecutrho and rrkj psp

[Stefano de Gironcoli]

rrkjus refers to an US pseudopotential geerated in two steps. first a 
hard NCPP is generated according to the rrkj recipe and then an USPP is 
generated whose augmentation charges reproduce the one of the previous NCPP.

stefano

On 01/31/2011 01:31 PM, Davide Sangalli wrote:
> Thanks for the answers to question 1.
> So rrkjus from quantum espresso are not norm conserving (indeed I'm using rrkjus
> psps).
>
> I supposed that rrkj means a pseudo created according to the rrkj scheme
> presented in PRB 41, 1227 (1990).
> In that paper the proposed psps are norm-conserving. Is that correct?
> Is there any another paper I should look for?
>
> Regards,
> Davide
>
> On 01/31/2011 12:41 PM, Davide Sangalli wrote:
> >  Dear forum,
> >  I'm doing calculations with rrkj pseudo-potentials.
> >
> >  As far as I understand rrkj are norm-conserving psps and only ecut should be
> >  checked, while ecutrho=4*ecut should be fine.
> >   From this I guess that the ecutrho paramater, if increased, should not
> >  influence the convergence.
> >
> >  I did some test and I saw that this is not true. Increasing ecutrho (at fixed
> >  ecut) the results changes significantly. For example the elements of the
> >  stress tensor changes more than 15 Kbar (in some case even more) moving
> >  ecutrho from 140 to 300 Ry (with ecut=35 Ry). Here I was testing FeO, CoO and
> >  NiO, with pbe/rrkj psps for all thee elements.
> >  *Question 1: Why ?
> >  *(I saw that in the psps header Rcut and Rcut US are different ... ?)
> >
> >  I did these checks even because I would like to perform calculations using
> >  vanderbilt psp (for some elements) together with rrkj psp (for other element?).
> >  *Question 2: Is there any counter indication in doing that ?
> >  *
> >  Thanks and best regards,
> >  Davide Sangalli
>
>
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