[Wien] Need advice for modeling the band gap in a charge transfer insulator

[David Tompsett]

Hi Shamik,

DFT+U can sometimes give a reasonable description of materials with some
charge transfer (possibly also some Mott) insulating character eg. NiO. But
it seems that in your case itinerant states are important to the band gap
and in that case using Hybrid functionals that include exchange between all
states (including itinerant ones) often helps eg. MnO. I think a full hybrid
functional set will come out in an upcoming version of Wien2k?

Some references:
Tran et al.
PHYSICAL REVIEW B 83, 235118 (2011)

Best,
David.

2011/10/25 shamik chakrabarti <shamikphy at gmail.com>

>
> Dear wien2k users,
>
>                             We all know that LSDA (or GGA)+U can be used
> successfully for a Mott-Hubbard insulator. Anisimov et al. [PRL 99, 156404
> (2007)] have described that for a charge transfer insulator we need to use
> LDA+DMFT for modelling their band structure properly. Now my question is :
>
> (1) Is their any option in wien2k by which we can use LDA+DMFT?
>
> (2) In our calculation after applying GGA+U (U for d orbital of TM) we saw
> that although there are a band gap between spin up & spin dn d DOS of
> transition metal, there are ligand (O p) DOS at Fermi Energy which is making
> our material metallic while experimentally it is an insulator [conductivity
> ~ 10^(-7)]. Here should we apply some value of U (say 0.15 Ry) for O p
> orbital also?
>
> (3) Any other advice regarding to this problem will be highly appreciated.
>
> Thanks in advance.
>
> yours faithfully,
> --
> Shamik Chakrabarti
> Senior Research Fellow
> Dept. of Physics & Meteorology
> Material Processing & Solid State Ionics Lab
> IIT Kharagpur
> Kharagpur 721302
> INDIA
>
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>
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