Hello, Actually, this is the LDA (and not PBE) exchange-correlation functional which is used for the energy when MBJLDA is used for the potential (option 28).
If you want PBE for the energy you have to replace exu=2.d0*(exupls + eclsd) exd=2.d0*(exdnls + eclsd) by exu=2.d0*(exuppb + ecpbe) exd=2.d0*(exdnpb + ecpbe) in the part of the subroutine vxclm2.f which concerns option 28. Then you recompile the lapw0 package. Maybe, the antiferromagnetic state will be the lowest again? F. Tran On Wed, 6 Apr 2011, davgumo wrote: > Dr. Blaha, thank you very much for your comments. > What is a bit?confusing?about my case is that my very first calculation with > PBE identifies the ground state in some peculiar antiferromagnetic insulator > (very small band gap though) this result was expected. Now when I try to > improve the band gap by performing mBJ calcs, I find that this magnetic order > which once I identified as the ground state is no longer lowest in energy. In > fact, I found out that the nonmagnetic case is much lower in energy according > to mBJ. > > Once again, it was expected that the ground state would be found as an > antiferromagnetic insulator as shown with PBE. > > Do think that mBJ somehow has trouble determining the ground state for this > crystal? > > I appreciate so much your help and the time you devote to all the users. > ? > By the way, we will soon have some experimental measurements about the band > gap of this crystal, I hope the calculated mBJ band gap agrees with the > experiment this would be very nice.? > > David Guzman M > Department of Physics & Astronomy > California State University-Los Angeles > (310)528-4841 > > On Apr 05, 2011, at 10:42 PM, Peter Blaha <pblaha at theochem.tuwien.ac.at> > wrote: > > Clearly, mBJ is only a POTENTIAL, not an energy-functional. > In fact, the mBJ option in WIEN2k uses the PBE-energy-functional, but > of course with the electron density (and spin-density) corresponding > to mBJ. > > The question whether you can trust the mBJ/PBE results more than the PBE/PBE > results is not so easy to answer and may depend on the specific case. > > If your compound belongs somehow to the cuprate-family (with CuO2 planes > and a Cu2+ ios) and you should get a significant Cu-moment. the chances are > high > that PBE does not get the correct groundstate (insulator ? magnetism ?), i.e. > both the PBE-density and the PBE-energy are "wrong". > > The mBJ-density should be more reliable in this case and maybe ??? the > PBE-energy for such a density is "better". > > At least I would "backup" the mBJ results by some LDA+U or hybrid-DFT > calculations. > > Am 06.04.2011 05:38, schrieb davgumo: > > Dear Wien users and Dr. Blaha > > > > I have been performing first-principles calculations on a recently > > synthesized crystal structure CuZrTiO5. > > This is a copper oxide the exhibits some potential to be a high Tc > > superconductor under doping. > > > > First I was interested in finding the ground state, which according to PBE > > calculations turns out to be in some antiferromagnetic order. After this I > > was interested in > > using mBJ to calculate an accurate value for the band gap, so I performed > > mBJ calculation on this antiferromagnetic order where I found the lowest > > energy. Recently I > > decided to run mBJ calculations on all the possible magnetic cases for this > > crystal. To my big surprise when I checked the energies calculated with mBJ > > the lowest energy is > > not longer on the magnetic configuration I found the ground state to be > > according to the PBE calculation. > > > > My question is if mBJ calculations are meant only to improve the band gap > > and will not provide the ground state of the system > > > > I appreciate any comments, hints, critics, etc that can help me to figure > > this out, and get a better understanding of the mBJ potential. > > > > Thank you very much. > > > > I can provide more details if this is not clear. > > > > David Guzman M > > > > Department of Physics& Astronomy > > California State University-Los Angeles > > > > > > > > > > _______________________________________________ > > 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 > ----------------------------------------- > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >