[Pw_forum] LSDA+U calculation on band gap

[Peng Chen]

Dear Dr. Burak,

U is different for AFM and FM states? The problem now is I can not make the
U calculation correct.  Dr. Matteo is helping me with great patient, but
still no luck now.

On Wed, Aug 8, 2012 at 2:49 PM, Burak Himmetoglu <himm0013 at umn.edu> wrote:

> 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
>>
>>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
  Best Regards.
        Peng
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20120808/5ea0d29b/attachment.html>