[Wien] Choice of Coulomb Energy

[Uday]

Dear Hong and Laurence,

Thank you very much for your valuable suggestions.

Regards,
Uday


> Dear Uday,
> For the 4f orbitals of lanthanide ions, the value of U in the range of 5
> - 7 eV should be quite reasonable. In particular, for Ce, I did some
> constrained DFT calculations in WIEN2k some time ago, and I got Ueff =
> U-J ~ 6.2 eV. But this value can not be taken too serious since it
> depends on some technical parameters. In a early study by S. Fabris et
> al (PRB 72, 237102 (2005)), the U for Ce obtained from a linear response
> approach is about 5.3 eV. Considering the uncertainty related to the way
> to calculate U, I think U=5 - 7 eV for lanthanide ions is a reasonable
> estimation. That is why in our study of lanthanide oxides using
> GW at LDA+U, we use Ueff=5.4 eV, and we have obtained quite good agreement
> with experiment for the band gaps of Ln2O3 (H. Jiang et al. PRL 102,
> 126403 (2009); PRB 86, 125115 (2012)).
>
> Hong
>
>
> 于 2013/6/17 21:30, Uday 写道:
>> Dear Wien2k users and Prof. Blaha,
>> I am working on a "Ce" based magnetic system. I tried to do LSDA+U with
>> different values of U from 0 to 6 eV for Ce-4f sate. U=0 eV gives the
>> minimum energy and total energy for the system increases as we increase
>> U
>> value. Also the DOS for Ce-4f keeps on shifting with increasing U. My
>> question is how to choose a correct U value for a system when a
>> spectroscopic data is missing?
>> Any help will be appreciated.
>>
>> Regards,
>> Uday
>> Dept. of Physics
>> IIT Kanpur
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