[Pw_forum] inconsistent quadrupolar coupling from gipaw calculation

[Davide Ceresoli]

Dear Jia,
     restarting GIPAW after a DFT+U calculation works in 6.1. It
needs some fix in the SVN version (marked on my agenda).

Best,
     Davide



On 10/09/2017 06:20 PM, Jia Chen wrote:
> 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 
> <mailto: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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   Davide Ceresoli
   CNR Institute of Molecular Science and Technology (CNR-ISTM)
   c/o University of Milan, via Golgi 19, 20133 Milan, Italy
   Email: davide.ceresoli at cnr.it
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