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> 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 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 >> 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 -----------------------------------------
