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

[Dr. K. C. Bhamu]

Dear Prof. L. Marks,
Thanks for your suggestions.  Yes, WO3 is an insulator.

I am facing the same issue for WC (SG: 187).

I have worked on Ni(OH)2 and ZnO surfaces and I did not face any
difficulties there. Ni(OH) surface is also polar.

For the present case, I do not have much choice. I was asked to provide the
absorbance of some molecules on the (100) surface of WO3. The experimental
group is not using any substrate/support for it.

I will read up on oxide surfaces.

Thank you very much,
Bhamu








On Fri, Jun 25, 2021 at 12:46 PM Laurence Marks <laurence.marks at gmail.com>
wrote:

> 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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