Dear Karel, Thank you so much for your mail. It would be very helpful.
with kind regards, On Tue, 23 Feb 2021 at 02:05, Karel Vyborny <vybor...@fzu.cz> wrote: > Dear Shamik, > it is perhaps a better idea not to try to _calculate_ the U but rather, > use the arguments of the Hu&Metiu article you mentioned (J Phys Chem C > 115, > 5841) for either hybrid functionals or GGA+U with values Hu&Metiu argue to > give a reasonable gap, reaction energies etc. A quick GGA calculation for > TiO2 shows that already within the sphere of Ti atoms, there's > significantly > more than 18 electrons (which would correspond to nominal Ti^4+) so it is > wrong to think about ni=nj=0 (in terms of what you write below). If you > wish to convince yourself (personally, I'm all in for being skeptical!) > that some particular GGA+U calculations make sense, try comparing more > physical quantities (optical or photoemission spectra for example) to > anything that is available on the experimental side. > > Best regards, > > Karel > > > > > --- x --- > dr. Karel Vyborny > Fyzikalni ustav AV CR, v.v.i. > Cukrovarnicka 10 > Praha 6, CZ-16253 > tel: +420220318459 > > > On Fri, 19 Feb 2021, shamik chakrabarti wrote: > > > Dear Wien2k users, I am interested in > > calculating the reaction energy for the equation > > 2 TiO2 + H2 = Ti2O3 + H2O > > In this case, I should use U for Ti in Ti2O3. However, in > earlier research > > works it has been given that the same U should also be used for Ti in > TiO2. > > > > My query is as Ti exists as +4 state in TiO2 why at all we need to use U > for > > it? > > > > We know EU = U/2 SUM (ni, nj), however as ni & nj is zero for Ti in TiO2 > why > > should we also need to use U for Ti in TIO2? > > > > Waiting forward to your response. Thanks in advance. > > > > with regards, > > > > -- > > Dr. Shamik Chakrabarti > > Research Fellow > > Department of Physics > > Indian Institute of Technology Patna > > Bihta-801103 > > Patna > > Bihar, India > > > >_______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India
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