[Wannier] Recreating radial wavefunctions from pw2wannier90 or wannier90 outputs

[Stepan Tsirkin]

Dear  Erica, dear Lorenzo,

just to add to what Lorenzo said:

  * as far as I know mostly the PAW coded write the pseudo-wavefunction
    into the UNK files, therefore the number of nodes cannot be
    reproduced in Wannier functions. At least it is true for  VASP and
    QuantumEspresso. The reasons are twofold: (i) noone bothered to code
    plotting all-electron wavefunction, (ii) the all-electron
    wavefunction strongly oscillates near the core, therefore a very
    dense real-space grid is needed to represent it.
  * The Wannier function may have additional nodes far from the the
    center (usually near the neighboring atoms, or even further) but
    those are not related to the nodes of atomic wavefunctions.
  * According to the page http://www.wannier.org/features/ , Wannier90
    is interfaced with Fleur and Wien2k, but I am not familiar with
    those, I do not know if/how they write the UNK files.
  * I fully agree with Lorenzo's conclusion:
>     Finally, if all you need is a pretty picture, I don't think it is
>     worth it. If you need the correct all-electron wavefunction close
>     to the core, I'm not sure wannierization is the best method.

Regards,

Stepan


On 03.11.20 10:41, Lorenzo Paulatto wrote:
>
>
> On 11/3/20 7:55 AM, Erica Kotta wrote:
>> The plots in xcrysden I've come across only show the lowest-level 
>> orbitals for each l-value (for example only 2p orbital character, 
>> even when you know that the bands of interest are 3p or 4p). I 
>> thought that by getting the underlying xsf numerical data or 
>> recreating the plots from the Umn/UNK files, I would be able to 
>> resolve the "missing" nodes.
> Hello Erica,
> this is not a limitation of the wannierization method, but of the 
> pseudo-potential approximation. The Wannier90 only works with what it 
> gets from the total energy code.
>
> I don't know if Wannier90 can interface with any all-electron code
>
> In principle if you use PAW pseudopotential, or with a GIPAW-like 
> method, it is possible to reconstructs the all-electron wavefunctions 
> from a pseudopotential calculation, but I do not think it has ever 
> been done in conjunction with wannierization.
>
> Finally, if all you need is a pretty picture, I don't think it is 
> worth it. If you need the correct all-electron wavefunction close to 
> the core, I'm not sure wannierization is the best method.
>
> cheers
>
>
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