[Wien] Basic question regarding band gap calculation using GGA+U approach

[shamik chakrabarti]

Dear wien2k users,

                           We know that charge transfer type band gap
(transition metal d - oxygen p) is generally underestimated in simple DFT
calculation. Situation may improve a bit by using DFT+U approach, however,
more accurate band gap may be found in Hybrid-DFT calculation.

Now, my question is that is there any scaling factor by which the
underestimation for a charge-transfer type gap in a simple DFT calculation
can be approximated.

Say, in a simple DFT we have found 0.5 eV gap for charge transfer type
states...then whether it can be said that the accurate gap may be 1.5
eV...that mean there is an underestimation of 1 eV for a charge-transfer
type gap in simple DFT calculation......whether there is any such thumb
rule like that or it strictly depends on the system under consideration?

Any response in this regard will be very helpful for us.

Thanks in advance.

with regards,


-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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