Sorry Peter, that is also wrong. The valence of a WO2 layer is 2+ ; of the O layer 2-. A valence neutral surface comes from a) Adding OH above every W -- 1- b) Add 1/2 the O above, and letting the structure relax in a 2x1 cell (or larger) -- the last layer has a valence of 1- per 1x1 c) Adjusting a top WO2 layer so it has a valence of 1+ per 1x1 (tricky)
Note: a) is for wet samples (in air); b) more common for dry but only if the top O can adequately bond; c) less common but not impossible. There is some literature, but I expect many of the existing calculations are dodgy. _____ 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, 07:16 Peter Blaha <pbl...@theochem.tuwien.ac.at> wrote: > 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.ma...@gmail.com <mailto:laurence.ma...@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 > > http://www.numis.northwestern.edu <http://www.numis.northwestern.edu > > > > > > On Fri, Jun 25, 2021, 01:59 Laurence Marks <laurence.ma...@gmail.com > > <mailto:laurence.ma...@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 > > http://www.numis.northwestern.edu < > http://www.numis.northwestern.edu> > > > > On Fri, Jun 25, 2021, 01:31 Dr. K. C. Bhamu <kcbham...@gmail.com > > <mailto:kcbham...@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 > > > > > > > > > > > > _______________________________________________ > > Wien mailing list > > Wien@zeus.theochem.tuwien.ac.at > > <mailto:Wien@zeus.theochem.tuwien.ac.at> > > > https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btL6FGi9Q$ > > < > https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btL6FGi9Q$ > > > > > > SEARCH the MAILING-LIST at: > > > https://urldefense.com/v3/__http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btzLCeneQ$ > > < > https://urldefense.com/v3/__http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btzLCeneQ$ > > > > > > > > _______________________________________________ > > Wien mailing list > > Wien@zeus.theochem.tuwien.ac.at <mailto: > Wien@zeus.theochem.tuwien.ac.at> > > > https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlRx1yD7_g$ > > < > https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlRx1yD7_g$ > > > > SEARCH the MAILING-LIST at: > > > https://urldefense.com/v3/__http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ > > < > https://urldefense.com/v3/__http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ > > > > > > > > _______________________________________________ > > Wien mailing list > > Wien@zeus.theochem.tuwien.ac.at > > > https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlRx1yD7_g$ > > SEARCH the MAILING-LIST at: > https://urldefense.com/v3/__http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ > > > > -- > -------------------------------------------------------------------------- > Peter BLAHA, Inst.f. 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