[QE-users] Query Regarding Band Structure Changes in DFT+U Calculations

[Stefano de Gironcoli]

this is what DFT+U is meant to do... you discourage partial occupation 
of certain localized orbitals. this of course changes the band structure 
and the share of different atomic l components for each state.

this is a desired effect when for instance you want to  open a gap in a 
material that otherwise would show partial occupation of these occupied 
orbitals... for instance FeO or Ce2O3

in your case the d bands are already either completely  occupied or 
completely empty... the U term just shifts them down or up according to 
the value of U you choose, changing the hybridization with the other 
states.

stefano

On 19/02/25 13:42, Zimmi Singh wrote:
> Dear Developers and Community,
>
> I have observed significant changes in the DFT eigenvalues, 
> particularly in the positions of the conduction band minimum (CBM), 
> when performing DFT+U calculations.
>
> In standard DFT calculations, the valence band maximum (VBM) is 
> located at the Γ point, while the CBM appears between Γ and 
> M. However, upon applying a Hubbard U correction (U= 2 eV), the 
> conduction band states shift upward for the spin-down channel and 
> downward for the spin-up channel. Additionally, the CBM relocates to 
> the K point in the Brillouin zone (see the attached image). Notably, 
> the overall topology of the CBM is drastically altered in the DFT+U 
> band structure. Furthermore, the projected density of states reveals a 
> significant change in occupancy.
>
> I would appreciate any insights into whether such modifications are 
> expected when incorporating Hubbard U corrections or if there might be 
> an issue in my calculations.
>
> I sincerely appreciate your time and suggestions.
>
> dft_and_dft+u-min.jpg
>
> -- 
> *Best Regards*
> Zimmi Singh
> /Research_Scholar
> /
> /Department of Metallurgical and Materials Engineering
> Indian Institute of Technology, Kharagpur
> Kharagpur, India/
>
>
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