[Wien] Choice of Coulomb Energy

[Hong Jiang]

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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