N.B., b) Does not work without massive rearrangements. A dangling "O" on top is unchemical.
There are many ways to construct wrong models! _____ 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, 07:43 Laurence Marks <[email protected]> wrote: > 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 <[email protected]> > 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 >> > <[email protected] <mailto:[email protected]>> 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 < >> [email protected] >> > <mailto:[email protected]>> 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 < >> [email protected] >> > <mailto:[email protected]>> 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 >> > [email protected] >> > <mailto:[email protected]> >> > >> 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/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btzLCeneQ$ >> > < >> https://urldefense.com/v3/__http://www.mail-archive.com/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Day7KZQBXQaPn8HGxSpldvOiJzObtS73z_8I17izzlA5ZmuvSj27rMzSsjCo-btzLCeneQ$ >> > >> > >> > >> > _______________________________________________ >> > Wien mailing list >> > [email protected] <mailto: >> [email protected]> >> > >> 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/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ >> > < >> https://urldefense.com/v3/__http://www.mail-archive.com/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ >> > >> > >> > >> > _______________________________________________ >> > Wien mailing list >> > [email protected] >> > >> 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/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!F0mxwQIGMo_vt5Lln6VGs_hFgnGILLIJ_nXqSLtWzLcjc3A2TrWel0YHCYz6UlTuloMcSQ$ >> > >> >> -- >> -------------------------------------------------------------------------- >> Peter BLAHA, Inst.f. 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