[Wien] Top surface layer seems to be isolated from the rest of the system

[Laurence Marks]

N.B., your cell is polar, and you are not satisfying valence neutrality or
Pauling's rules. It will never occur in reality, and any results you obtain
with it will move science backwards.

Read up on oxide surfaces, much is known.

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Györgyi
www.numis.northwestern.edu

On Fri, Jun 25, 2021, 01:59 Laurence Marks <laurence.marks at gmail.com> wrote:

> Did you check:
> a) The BVS, to ensure that you do not have a GIGO surface?
> b) Whether the system has a decent gap or not -- I believe WO3 should be
> an insulator.
> c) Whether you are satisfying valence neutrality at the surface.
>
> I expect you have a GIGO surface, 99.99% probability. You cannot just
> create an oxide supercell and expect it to lead to a realistic surface.
> Fixing layers won't help, and is flawed thinking.
>
> GIGO.
>
> _____
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Györgyi
> www.numis.northwestern.edu
>
> On Fri, Jun 25, 2021, 01:31 Dr. K. C. Bhamu <kcbhamu85 at gmail.com> wrote:
>
>> Dear Wien2k Users,
>>
>> I am trying to relax the WO3 surface structure (1x1x5 with 15 Ang
>> vacuum). The bulk structure crystallizes in  221 SG.
>> Then I created the 1x1x5 layered structure and relaxed the top two layers
>> with the bottom three layers kept fixed.
>> I see after relaxation, the top layer detached from the system (the W-O
>> bond length increased from 1.9 to 2.3 Ang), you can see from the PDF
>> provided with this email.
>> I have tried with QE as well and the same problem I faced there.
>> I am wondering if someone has faced a similar experience and would like
>> to share his/her experience with me to tackle this issue.
>>
>> I have used a different strategy: with U, with U, with dipole correction,
>> without dipole correction, vacuum up to 30Ang.
>>
>> As the bulk system is a high symmetry system, is it the reason due to
>> the symmetry? If so then how one can handle it?
>>
>> I am providing the required information here in the tar file  (PLEASE
>> DOWNLOAD FROM HERE
>> <https://urldefense.com/v3/__https://we.tl/t-0vedkrUS54__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-bt6MCzNAQ$>
>> ).
>>
>> I would appreciate it if someone shares their experience with me.
>>
>> Regards
>> Bhamu
>>
>>
>>
>>
>>
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