[Wien] ELF

Fri Nov 4 00:13:40 CET 2022

Dear Prof. Blaha
I apologize. Let me make my previous Email a little more complete. As you
mentioned in your Email, for SnS the sources of differences between the
results of ELF using WIEN2k code and VASP code is due to the difference
between all-electron and pseudopotentials calculations in these two codes.
However, I am still not sure that the differences between my results for
the ELF of SnSe and Jiawang and Olivier's paper are normal or not. I would
be glad if you let me know your opinion about this subject.
Sincerely yours
Reyhaneh Ebrahimi

On Thu, Nov 3, 2022 at 1:13 PM Peter Blaha <peter.blaha at tuwien.ac.at> wrote:

> Good to hear that this has been resolved.
>
> PS: I just did a SnSe calc. and compared with the VASP paper. Similarly,
> very good agreement in the interstitial, while inside the atomic cores
> there is the expected difference between all-electron and pseudopotentials.
>
> Am 03.11.2022 um 21:06 schrieb Kateryna Foyevtsova:
> > Dear Prof. Blaha,
> >
> > I think I know what's going on with ELF. Wien2k gets it correctly, but
> > Quantum Espresso has a bug which shows up in nspin=1 calculations. In
> > the attached figure I compare the wien2k result with two QE
> > calculations: (1) one with nspin=1 switch and (2) one with nspin=2
> > switch. In both cases I am looking at the same non-magnetic solution
> > that has the same energy in the two QE calculations.
> >
> > Now you see that the difference between QE nspin=1 and nspin=2 is
> > dramatic whereas there should be none.
> >
> > The wien2k result looks very similar to the QE nspin=2 result in the
> > interstitial region at 0.5,0.5,0.0, marked with a big purple "X". There
> > are differences close to atomic nuclei but this is expected given that
> > we are comparing an all-electron and a pseudo-potenial code.
> >
> > Thank you very much for helping me resolve this issue.
> >
> > Best,
> > Kateryna
> >
> > On 2022-11-02 12:21, Peter Blaha wrote:
> >> [CAUTION: Non-UBC Email]
> >>
> >> My result looks like the attached picture. I do get 0.8 in the core
> >> region of Ni, but not larger than that. It is probably similar than
> >> yours.
> >> I have no idea why it is different from QE, except maybe that these
> >> are pseudopotential calc.
> >>
> >> As I said before, you should compare other compounds, and also compare
> >> with literature ELF calculations.
> >>
> >>
> >>
> >> Am 01.11.2022 um 21:16 schrieb Kateryna Foyevtsova:
> >>> Dear Prof. Blaha,
> >>>
> >>> thank you for looking into this issue. I've tried the modified
> >>> create_rho.f and calculated the ELF of NdNiO2 again using create_elf.
> >>> I am getting a better agreement with QE, but it is not perfect as you
> >>> noted it too. My calculation was well converged and I used the same
> >>> k-grid and RKmax=7. The bandstructures from QE and wien2k agree very
> >>> well.
> >>>
> >>> I attach my comparison as a png file. I wonder whether you have any
> >>> idea about the possible reasons for the differences in ELF that the
> >>> two codes give? For example, at 0.5,0.5,0 the wien2k value is ~0.22
> >>> and the QE value is ~0.43.
> >>>
> >>> Thank you,
> >>> Kateryna
> >>>
> >>> On 2022-10-28 04:43, Peter Blaha wrote:
> >>>> [CAUTION: Non-UBC Email]
> >>>>
> >>>> Dear Kateryna ,
> >>>>
> >>>> In fact, I found a big difference between     create_elf   and
> >>>> x lapw0 (with VX_ELF); x lapw5 -exchange
> >>>>
> >>>> I traced it back to normalization errors in tau_w and tau_tf, which
> >>>> missed a factor of 2.
> >>>>
> >>>> The attached    create_rho.f  fixes the problem. It should be copied
> >>>> into SRC_trig; make
> >>>>
> >>>> Then you can use    create_elf   again.
> >>>>
> >>>> PS: I would always compare the ELF created with both methods as
> >>>> indicated above. Depending on the numerics, one or the other method
> >>>> may give smoother plots, but in any case, they should be very similar.
> >>>>
> >>>> PPS: The agreement to QE-ELF seems reasonable (but not perfect), but
> >>>> I've not converged my calculations.
> >>>>
> >>>> Thanks for the report
> >>>> Peter Blaha
> >>>>
> >>>>
> >>>>> I attach a pdf showing the differences. Also attached are my wien2k
> >>>>> >struct file and quantum espresso input file.
> >>>>
> >>>>> Both calculations were done without spin polarization and using PBE.
> >>>>
> >>>>> To me, the differences are big enough to question whether it is
> >>>>> >meaningful to use ELF at all if it depends on all-electron vs
> >>>>> >pseudopotential so strongly. Unless I am missing something or
> >>>>> doing >something wrong.
> >>>>
> >>>>> Thank you,
> >>>>> Kateryna
> >>>>
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> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300
> Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
> WWW:   http://www.imc.tuwien.ac.at
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