[Wannier] Wannier Digest, Vol 52, Issue 7

[Mario Burbano]

Jonathan,

Thank you for the suggestions for dealing with Gd-doped ceria. Everything
seems to be working as expected now. This is what I did with my .win file:

num_wann =   464
exclude_bands : 465-576
translate_home_cell = T
write_xyz = T
!postproc_setup = T
num_dump_cycles = 20
num_iter = 100
!gamma_only = T
!restart = default
length_unit = bohr
conv_tol = 1E-04
conv_window = 2

use_bloch_phases = F
  Begin Projections
  O:sp3
  Ce:sp3
  Gd:sp3
  c=0.07696275,11.00533316,10.77486182:l=3,mr=1
  c=0.07696275,11.00533316,10.77486182:l=3,mr=2
  c=0.07696275,11.00533316,10.77486182:l=3,mr=3
  c=0.07696275,11.00533316,10.77486182:l=3,mr=4
  c=0.07696275,11.00533316,10.77486182:l=3,mr=5
.........

Regards,

Mario Burbano



On Fri, Mar 30, 2012 at 08:46, <wannier-request at quantum-espresso.org> wrote:

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> Today's Topics:
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>   1. Re: Spin polarized calculations with f-electrons (Jonathan Yates)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 29 Mar 2012 22:49:57 +0000
> From: Jonathan Yates <jonathan.yates at materials.ox.ac.uk>
> Subject: Re: [Wannier] Spin polarized calculations with f-electrons
> To: Wannier90 <wannier at quantum-espresso.org>
> Message-ID: <51C42D6F-3C24-415E-9BA6-B10962C95F2E at materials.ox.ac.uk>
> Content-Type: text/plain; charset="Windows-1252"
>
>
> On 29 Mar 2012, at 10:09, Mario Burbano wrote:
> >
> > The results I have obtained so far for yttrium-doped CeO2 and
> scandium-doped CeO2 have been consistent with each other using either DFT
> program. By this I mean that the forces and the dipole moments obtained
> from the DFT codes show excellent agreement between them. However, it is
> when I carry out simulations with elements that have f-electrons (Ce3+,
> Gd3+, Sm3+) that I start having some serious problems. In the case of
> Gd-doped ceria, when I visualize the wannier90_centres.xyz file from the
> Wannier90 analysis of the data, I can see that the f-electrons that should
> have been assigned to Gd, have instead been localized near the nucleus of
> the Ce atoms, in addition to the expected 8 valence electrons. I have
> encountered similar problems with systems that include reduced cerium
> (Ce3+). In this case the single f-electrons from each Ce3+ are assigned to
> a single Ce atom (which according to the VASP output should not be
> reduced). These wannier centres are conspicuous among the others given that
> their spreads are typically higher (>4 Bohr^2) than those of all the other
> WCs in the system (2.5 ? 3 Bohr^2). In addition, the up and down spin
> components from the wannier90 calculation are the same, which, I think, is
> unexpected. Finally, a comparison with the results from CPMD is not
> available here because CPMD does not have the DFT+U method implemented.
>
> Mario,
>
>  I'm going to make some generic comments first, rather than think about
> the chemistry of your system. Although I don't think there should be
> particular issues in dealing with f-electron systems.
>
> You should investigate if the WF you have found correspond a true minimum
> in the spread functional.
>
> A good indication is to check how real the WF are.
> You are starting from random phases. What happens if you use a starting
> guess?
>
> You are using the gamma-point. Is the vasp interface set up to take
> advantage of the fact that the bloch states are real at gamma? (the PWSCF
> interface is) If so, you can use the gamma-point routines within W90. The
> special gamma point routines are quicker, and have been found to be more
> robust ie less reliant on the start guess.
>
>
>
>  Jonathan
>
>
> --
> Department of Materials, University of Oxford, Parks Road, Oxford, OX1
> 3PH, UK
> tel: +44 (0)1865 612797                http://users.ox.ac.uk/~oums0549/
>
>
>
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> End of Wannier Digest, Vol 52, Issue 7
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