Dear Bhamu

In the present case, you are dealing with Ag+ ions and thus a d10 electronic configuration for silver.

In such a case applying a Hubbard correction will mainly lead to correct the position of the Ag(4d) states which are all occupied and below the O(2p) band. It should not affect so much the band gap. Do you have the band gap values when doing PBE only?

I would recommend to do:

- PBE

- PBE+mBJ

- and if you want to see the impact of the proper description of the 4d band of silver which is too high in energy when doing PBE only, you can apply an Hubbard term

You must also consider the impact of relativistic treatment. For silver, the spin-orbit coupling will lead to split the p1/2 and p3/2 states which could contribute to the conduction band.

Best Regards

Xavier


Le 27/11/2016 à 16:19, Dr. K. C. Bhamu a écrit :

Dear experts
I did a calculation for hexagonal AgAlO2 and found that if I do first PBE+U and then apply mBJ+ U, it give smart band gap value which is very close to experimental band gap.

But I do not know whether we can apply this U twice or not.
The DFT+U calculation underestimates and only mBJ slightly overestimate the experimental band gap for this system.

I did the calculation for -ec 0.00001 -cc 0.0002 -fc 2 (setrmt -r 5).

Any comment will be helpful.

Sincerely
Bhamu



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