[Wien] Top surface layer seems to be isolated from the rest of the system
Peter Blaha
pblaha at theochem.tuwien.ac.at
Fri Jun 25 14:16:23 CEST 2021
Remove the O atoms, which are sticking out of the lower surface.
This makes the system inversion symmetric and more realistic.
Since you are now not stoichiometric anymore, eventually test with more
than 5 layers .
Am 25.06.2021 um 13:42 schrieb 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 <mailto: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 <http://www.numis.northwestern.edu>
>
> On Fri, Jun 25, 2021, 01:59 Laurence Marks <laurence.marks at gmail.com
> <mailto: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 <http://www.numis.northwestern.edu>
>
> On Fri, Jun 25, 2021, 01:31 Dr. K. C. Bhamu <kcbhamu85 at gmail.com
> <mailto: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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