I have come across a review that cites CASTEP as yielding corrected band gap of ZnO using DFT+U, approx. equal to experimental band gap of ~3.38 eV. The VASP results were still smaller after correction with DFT+U in the review. Does any one know of any literature that uses VASP DFT+U to get ZnO band gap values close to experimental one?
Did you test the effect of U values on the final results? You may use different values. In fact, the U value can be estimated from the self-consistent response calculation.
Thank you Wenzhong, Philip, and Zahara.
I had the review paper you cited, Zahara. Philip, it is the first paper in Zahara's list.
Wenzhhong,
The review paper has a table listing three papers based on VASP code. Two of the results are similar to what we get, around 2 eV for the band gap. There is a third paper in J. Phys. Chem.C that claims it has achieved Eg of 3.4 eV which is equal to the experimental value. Damilola Dada has posted another thread on this forum. Please see details of VASP inputs we used on that post. And if you are a VASP user and can suggest or get the same band gap, it would validate the DFT+U approach for us for further work.
Philip:
The CASTEP results are three using GGA+PBE+U in the table. One of them only has the experimental value for the band gap. I am in the process of getting CASTEP license and will contact you when I get it.
M
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