Read the paper Am 18.08.2012 18:59, schrieb Jameson Maibam: > Dear sir, please suggest suitable exchange correlation for ZrO2 in monoclinic > structure. Its reported band gap using GoWo is 5.34eV . My experimental > groups got 5.5eV. > Yours sincerely > Jameson Maibam > > ----- Original Message ----- > From: Peter Blaha <pblaha at theochem.tuwien.ac.at> > To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at> > Cc: > Sent: Saturday, 18 August 2012 10:15 PM > Subject: Re: [Wien] Okay to combine mBJ, spinorbit, and LDA+U? > > Yes, the Zn-3d states are very localized (like the 4f) and some U (much > smaller than what you would use in GGA+U) > will give you the experimental gap. > > Alternatively you can use modified mBJ parameters (PRB 85, 155109) which are > tailored more towards semiconductors > (gaps below 5 eV) and bring the ZnO gap above 3.2 eV. > > Am 18.08.2012 18:27, schrieb Kamil Klier: > > Thanks Fabien, > > > > Indeed the match between MBJLDA theory and experiment (Fig. 1 in the > quoted paper) is excellent. > > > > However, the bandgap of ZnO is underpredicted by mBJ only, reading from > Fig. 1 ca. 2.8 eV. This would render zinc oxide colored in the visible > region, but pure ZnO is > > white, in accord with experimental bandgap 3.2 - 3.4 eV. Moreover, the > Zn3d_10 (filled) narrow band falls below the O2p valence band (from VB XPS) > while a quick > > calculation with MBJLDA results in blending of O2p and Zn3d. Is it > possible that in the ZnO case the U (say U_eff = 0.46 Ry) would help a bit as > follows: it would push the > > Zn3d down and improve the bandgap - unless of course there are theoretical > reasons why mBJ and U should be in conflict. That does not seem to be the > case, however, for 4f > > orbitals. > > > > Best regards, > > > > Kamil Klier > > > > Quoting tran at theochem.tuwien.ac.at <mailto:tran at > theochem.tuwien.ac.at>: > > > >> Yes, mBJ alone is already ok for NiO: > >> http://prl.aps.org/abstract/PRL/v102/i22/e226401 > >> So, adding U is not a good idea. > >> > >> On Sat, 18 Aug 2012, Kamil Klier wrote: > >> > >>> The Wien example for NiO uses U_eff = 0.52 Ry for the Ni3d orbitals. > >>> > >>> Would that mean that using subsequent mBJ potential for 'improvement of > >>> bandgap of NiO' is not appropriate or at least is an overkill? > >>> > >>> Best regards, > >>> > >>> Kamil Klier > >>> > >>> Quoting Peter Blaha <pblaha at theochem.tuwien.ac.at <mailto:pblaha at > theochem.tuwien.ac.at>>: > >>> > >>> >mBJ+U is appropriate for 4f systems only (because mBJ is too weak to > fully > >>> >localize the 4f electrons). Do not use it for d-electrons. > >>> > > >>> >mBJ is made to give a good bandstructure. We have evidence, that the > >>> >resulting > >>> >electron density is too ionic, thus a force optimization using MSR1a > could > >>> >be problematic (although it could be better than GGA in some cases > (with 3d > >>> >electrons - Jahn-Teller distortions). > >>> >Eventually, MSR1a with the original BJ potential (c=1) is physically > more > >>> >justified, sind original BJ is an approximation to OEP (optimized > effective > >>> >potential), > >>> >which should be close to the "exact local exchange-only" potential. > >>> >(Note that an "exact exchange potential" + LDA-correlation can be much > more > >>> >wrong than plain LDA !!!!! for certain cases, because we miss the error > >>> >cancellation) > >>> > > >>> >before doing Spin-orbit calculations, I'd remove case.in0_ggr and use > the > >>> >case.grr file from the scf-mBJ calculation without SO. I do not trust > >>> >the kinetic energy densities with SO. > >>> > > >>> > > >>> >Am 16.08.2012 22:15, schrieb Laurence Marks: > >>> > >If it is a decent insulator I would do LDA+U directly; often it > >>> > >converges better and since the lattice parameter and forces change you > >>> > >do not gain much by first doing LDA/GGA. Normally LDA+U is stable, > >>> > >often more stable that LDA/GGA. Volume optimization should be done > >>> > >first, then min_lapw or MSR1a. Better is to do MSR1a or min_lapw at > >>> > >each volume. > >>> > > > >>> > >Then add -so, mBJ as appropriate with the optimized positions. > >>> > >However, I not sure if mBJ+U is appropriate (I doubt that it is). It > >>> > >might be that LDA+U positions are a better approximation for mBJ, not > >>> > >sure. One way is to minimize the forces with mBJ using MSR1a (not > >>> > >min_lapw/PORT) and compare them to LDA+U. If they are the same then > >>> > >you are in good shape, needs testing. Maybe someone has.... > >>> > > > >>> > >N.B., it is completely fine to minimize positions in mBJ using MRS1a > >>> > >-- do not use min_lapw/PORT, it will not be correct. MSR1a does not > >>> > >care that the energy is incorrect whereas min_lapw/PORT does. > >>> > > > >>> > >On Thu, Aug 16, 2012 at 2:44 PM, Jeff Spirko <spirko at lehigh.edu > <mailto:spirko at lehigh.edu>> wrote: > >>> > > >Is it okay to use spinorbit and LDA+U with mBJ? > >>> > > > > >>> > > >I would guess it is done like this: > >>> > > > * Check that forces <10 mRy/au with plain LDA or GGA. Reduce via > >>> > > > min_lapw. > >>> > > > * Volume optimization (if desired) with plain LDA or GGA to reduce > >>> > > >absolute pressure. > >>> > > > * Set up LDA+U (Sec 4.5.6) and use -orb flag from now on. > >>> > > > * Need to converge LDA+U??? > >>> > > > * Follow mBJ instructions (Sec 4.5.9). > >>> > > > * After mBJ+LDA+U is converged, follow spinorbit instructions (Sec > >>> > > > 4.5.5). > >>> > > > * For spinpolarized, check whether atoms became nonequivalent > >>> > > >(affects case.inso, case.inorb, > >>> > > > case.indmc, case.in1c, basically any input file with atom lists > or > >>> > > > indices) > >>> > > > * touch .fulldiag (necessary because klist can change???) > >>> > > > * Do final run with -so -orb > >>> > > > > >>> > > >Best regards, > >>> > > >-- > >>> > > >Jeff Spirko spirko at lehigh.edu <mailto:spirko at lehigh.edu> > WD3V |=> > >>> > > > > >>> > > >The study of non-linear physics is like the study of non-elephant > >>> > > >biology. > >>> > > >_______________________________________________ > >>> > > >Wien mailing list > >>> > > >Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at > zeus.theochem.tuwien.ac.at> > >>> > > >http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >>> > > > >>> > > > >>> > > > >>> > > >>> >-- > >>> >----------------------------------------- > >>> >Peter Blaha > >>> >Inst. Materials Chemistry, TU Vienna > >>> >Getreidemarkt 9, A-1060 Vienna, Austria > >>> >Tel: +43-1-5880115671 > >>> >Fax: +43-1-5880115698 > >>> >email: pblaha at theochem.tuwien.ac.at <mailto:pblaha at > theochem.tuwien.ac.at> > >>> >----------------------------------------- > >>> >_______________________________________________ > >>> >Wien mailing list > >>> >Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at > zeus.theochem.tuwien.ac.at> > >>> >http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >>> > > >>> > >>> > >>> > >>> ---------------------------------------------------------------- > >>> This message was sent using IMP, the Internet Messaging Program. > >>> > >>> _______________________________________________ > >>> Wien mailing list > >>> Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at > zeus.theochem.tuwien.ac.at> > >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >>> > >> _______________________________________________ > >> Wien mailing list > >> Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at > zeus.theochem.tuwien.ac.at> > >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >> > > > > > > > > ---------------------------------------------------------------- > > This message was sent using IMP, the Internet Messaging Program. > > > > _______________________________________________ > > Wien mailing list > > Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at > zeus.theochem.tuwien.ac.at> > > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -- > ----------------------------------------- > Peter Blaha > Inst. Materials Chemistry, TU Vienna > Getreidemarkt 9, A-1060 Vienna, Austria > Tel: +43-1-5880115671 > Fax: +43-1-5880115698 > email: pblaha at theochem.tuwien.ac.at <mailto:pblaha at > theochem.tuwien.ac.at> > ----------------------------------------- > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at zeus.theochem.tuwien.ac.at> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >
-- ----------------------------------------- Peter Blaha Inst. Materials Chemistry, TU Vienna Getreidemarkt 9, A-1060 Vienna, Austria Tel: +43-1-5880115671 Fax: +43-1-5880115698 email: pblaha at theochem.tuwien.ac.at -----------------------------------------
