[Pw_forum] inconsistent quadrupolar coupling from gipaw calculation

[Jia Chen]

Dear Davide,

Thank you very much for this. I will try to do some more digging into this
issue. It seems to me elk is the way to go, since wien2k is commercial and
I have no access to it .

I have one more question about gipaw with DFT+U. If I am only interested in
chemical shift, is gipaw fully functional with DFT+U, for both
norm-conserving and ultra-soft pesudopotentials? Does DFT+U type in pwscf
matter for gipaw? I noticed some issues in calculations, but I would like
to know what the code is supposed to do at this stage before reporting it.

Cheers

On Mon, Oct 9, 2017 at 8:13 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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