[Pw_forum] inconsistent quadrupolar coupling from gipaw calculation

[Ary Junior]

Hi Jia,

I would start with Elk and I'm sending an example input file. More
information about essential convergence tests necessary to obtain some
initial results can be found at

http://elk.sourceforge.net/faq.html
http://elk.sourceforge.net/elk.pdf

Try starting with the default atomic species configuration files.

Cheers!

Ary Ferreira

FAPESP postdoctoral fellow
UFSCar - Brazil

On Mon, Oct 9, 2017 at 9:13 AM, Davide Ceresoli <davide.ceresoli at cnr.it>
wrote:

> Dear Jia,
>      I have to admit that this is the first time that NMR/EFG results
> depend so much on the choice of the pseudopotential. I've calculated
> a bunch of minerals, both with NC and US pseudos, and results are
> in good agreement each other.
>
> I've tested several Co pseudos (NC, NC+semicore, PAW+semicore) on
> Co3O4 spinel and the EFG results span the entire real numbers range,
> both for Co and for O.
>
> Which one is correct? I don't know. I'm in favor of pseudopotentials
> with semicore states. They should be closer to all-electron.
>
> Do you have some reference with Co EFG calculated all-electron (wien2k,
> elk/exciting) on some simple system? If not, is there someone that
> could help us to setup a wien2k/elk calculation?
>
> Best regards,
>      Davide
>
>
>
>
>
> On 09/20/2017 06:50 PM, Jia Chen wrote:
> > Dear All,
> >
> > I am working on calculating nmr parameters with gipaw code. I have two
> settings:
> > one with norm-conserving gipaw pesudopotentials which has some semi-core
> states,
> > and the other with ultra-soft gipaw pseudopotentials. Electronic
> structure
> > eigenvalues from pwscf look similar, and chemical-shift are not far away
> from
> > each other. The issue is quadrupolar coupling, for Co, norm-conserving
> > calculation gives 0.5MHz and ultra-soft gives 1.5MHz. It seems to me a
> > significant discrepancy.  I don't know what caused the inconsistency,
> and which
> > one is more reliable. I appreciate any insight on this problem.
> >
> > One thing about norm-conserving calculation is that the code gives
> warming about
> > some orbitals has zero norm. I don't know if that could be of concern.
> >
> > Cheers
> > Jia
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