[Pw_forum] XSpectra and US or PAW pseudos?

[Lorenzo Paulatto]

On Monday, August 31, 2015 02:36:34 PM Adrian Hühn wrote:
> Besides Matteo said XSpectra is not compatible with PAW so. And he was
> involved in the implementation of the Lanczos algorithm with USPPs (PRB
> 80, 075102 (2009)). I will try to do some small test calculations, for
> comparison.
> 

Let's see if Matteo answers.. (we work in the same place, but I'm not with him 
at the moment)

> -------------------
> Its reference state is the atomic ground state. GIPAW projectors are the
> same as PAW (?).To create the core-hole PP one should change the config
> tag to

Yes, GIPAW and PAW will use the same projectors, this may not be optimal as 
the level of precision required for a PAW calculation may be not as fine as 
that required for GIPAW. I think it will work for most cases.

> 
> ---
>     config='1s1 2s2 2p6 3s2.0 3p0 3d-2',
> ---
> 
> and I am done.

Well, I would print the wavefunctions to file, keywords:
   file_wfcusgen   ='ultrasoft_wfcs_file'*
   file_wfcaegen   ='all-electron_wfcs_file'
   file_wfcngen   ='nor-conserving_wfcs_file'**
(* Ultrasoft or PAW pseudo-wavefunctions)
(** only used for norm-conserving and ultrasoft, when PSQ=.false.)

To check that the new pseudo-wavefunctions look similar to the old one, and 
reduce the pseudization radii a bit if necessary.

> 
> What about USPP? The associated Mg USPP looks like the same:

The same as PAW.

> Creating the core-hole should trivially apply here as well. But how do I
> consistently add GIPAW information? Do I take simply the same radii? How
> does the syntax look like?

I do not know very well, I guess you may have to test for the completeness of 
the basis.

> For the normconserving case it is nicely described in the tutorial so no
> questions here :-).

I guess for ultrasoft is just the same, but I have not read the tutotial.

> 
> A further question: In the tutorials it was suggested to ionize the
> reference state a bit. Is this crucial?

I don't think so. If you where taking away some charge to make the neutral 
atom more stable, this is probably no more necessary when you put a 1s hole. 
Although, save the wavefunctions to file, plot them check for weird features 
(like big bumps or extra nodes in the pseudo wavefunction close to the origin)

> 
> Regards
> Adrian
> 
> Am 31.08.2015 um 12:53 schrieb Lorenzo Paulatto:
> > On Monday, August 31, 2015 11:49:28 AM Adrian Hühn wrote:
> >> How do I correctly include a reference state to a pseudopotential from
> >> the PSlibrary?
> > 
> > At the beginning of the .UPF file you normally find a copy of the input
> > used to generate it, you can then regenerate the pseudo adding reference
> > information for GIPAW (ask further if you need help about this).
> > 
> > About PAW dataset not being compatible, I think they can be if you
> > generate
> > them with the use_paw_as_gipaw=.true. keyword, but I leave the final word
> > to experts or to testing .
> > 
> > regards
> 
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-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
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