[Wien] ELF

Thu Nov 3 21:13:26 CET 2022

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
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Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
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