[Pw_forum] LSDA+U calculation on band gap

[Peng Chen]

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
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