Hello Peng, One can compute U for the AFM and FM states separately using linear response. Then, using the calculated U values for each state, you can recompute the gaps. This approach might resolve the issue.
Best regards, Burak On Wed, Aug 8, 2012 at 1:00 PM, Peng Chen <pchen at ion.chem.utk.edu> wrote: > Dear All, > > According to the experiments, the material's ground state is afm and the > band gap is ~2.30 eV in 4K. > In the magnetic field, the spin moments are aligned in the field direction > (we call it "fm state") and the > band gap is ~2.34 eV. But from the calculation results, when U>=5 eV, the > fm spin up gap is less > than that of afm state which is different from experimental results. (I > guess we should choose spin > up gap to represent fm state gap since spin down gap is larger). From the > calculated gap value, > U=8 eV is close to experimental results, but the gap in fm state is less. > Please let me know what > I can do to improve the results? > > > U afm gap fm spin up fm spin down > 4 1.49 1.723 1.731 > 5 1.81 1.77 2.01 > 6 1.922 1.912 2.273 > 8 2.265 2.076 2.634 > > > -- > Best Regards. > Peng > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120808/ec1c8bae/attachment.htm