[Wien] ELF
Kateryna Foyevtsova
foyevtsova at phas.ubc.ca
Fri Nov 4 22:06:28 CET 2022
Hello,
since I see that VASP results are being discussed here, I'd like to
bring your attention to my communication with the VASP developers in
April this year:
https://www.vasp.at/forum/viewtopic.php?f=3&t=18484
where they admitted that "the current implementation depends strongly on
the choice of the POTCAR. You can test this by using the GW POTCAR and
will find contributions from Ni 3d electrons. We believe that with this
pseudo-potential dependent ELF is not a good measure for electronic
localisation and thus want to replace this (very old) implementation in
a future release."
which means that ELF calculated in the current version (and all earlier
versions, apparently) of VASP can have errors and should not be used as
a gold standard. I think they still have not fixed that bug according to
https://www.vasp.at/forum/viewtopic.php?f=4&t=18628&p=22510&hilit=elf#p22510
Best,
Kateryna
On 2022-11-04 13:11, reyhaneh ebrahimi wrote:
> [CAUTION: Non-UBC Email]
>
> Dear Prof. Blaha
> Thank you for your valuable answer to my Email.
> I put my ELF graph, your ELF results, and Jiawang and Olivier' graph
> for SnSe on one page to have a better comparison, see
> "https://www.mediafire.com/file/kyfi46ppx6mhtnx/SnSe-final.jpg/file".
> I also specified the plane which I did my ELF calculation on it.
> Therefore, as you mentioned in your Email, the existing differences
> between my graph, your graph, and Jiawang and Olivier' graph would be
> due to the choice of different planes in these works.
> Sincerely yours
> Reyhaneh Ebrahimi
>
> On Fri, Nov 4, 2022 at 8:33 AM Peter Blaha <peter.blaha at tuwien.ac.at>
> wrote:
>
>> Sorry: the links should be: SnSe, not SnGe
>>
>> http://www.wien2k.at/Depository/SnSe-f.png
>> http://www.wien2k.at/Depository/SnSe-g.jpg
>> http://www.wien2k.at/Depository/SnSe-t.png
>>
>> Am 04.11.2022 um 15:27 schrieb Peter Blaha:
>>> Your picture for SnSe is probably in a different plane as compared
>> to
>>> the 4 pictures in the paper.
>>> I produced 2 elf pictures, which resembles the planes in Fig. 6f
>> and 6g.
>>>
>>> They look as expected. In the interstital identical (see eg. the 2
>>
>>> different blue features in 6f), but inside the spheres quite
>> different
>>> because of the pseudopotentials.
>>>
>>> I guess it is a general feature that inside spheres (and for
>> heavier
>>> atoms) the PP ELF is nonsense.
>>>
>>> You can download them at:
>>>
>>> http://www.wien2k.at/Depository/SnGe-f.png
>>> http://www.wien2k.at/Depository/SnGe-g.jpg
>>> http://www.wien2k.at/Depository/SnGe-t.png
>>>
>>>
>>> Am 04.11.2022 um 00:13 schrieb reyhaneh ebrahimi:
>>>> 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
>>>> <mailto: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
>> <mailto:peter.blaha at tuwien.ac.at>
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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
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--
Kateryna Foyevtsova, PhD
Research Associate
Stewart Blusson Quantum Matter Institute
The University of British Columbia | Vancouver
261C - 2355 East Mall | Vancouver BC | V6T 1Z4 Canada
Phone +1 (604) 822-8545
foyevtsova at phas.ubc.ca
www.sbqmi.ubc.ca
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