I'm looking for the answer. What is the significant of this difference in the practical applications???
Dear M Liton,
It would be better to clarify what you mean by "in DFT", if theoretically or in actual calculations.
Given this disclaimer, this question resurfaces regularly, you can check answers with different degrees of complexity here in Researchgate.
Two articles might help to clarify this question:
Article Mind the gap!
Article The Kohn–Sham Gap, the Fundamental Gap and the Optical Gap: ...
Hope this helps.
Best regards!
Two aspects, aside from the imprecisions that Gabriel Ravanhani Schleder already adressed properly:
1) If the material has an indirect bandgap, i.e. the highest valence and the lowest conduction band location are at different locations in the k space, you cannot directly excite that. The optical bandgap is the minimum difference of bands at the same k space location which is equal to the electronic one only for a direct bandgap.
2) You mention "DFT": DFT is only an approximation and there is no systematic law whether the bandgap from there will be larger or smaller than the experimental one, that is only determined by benchmark. However, aspect 1) stays valid if you look at calculated band gaps.
"The optical bandgap is the minimum difference of bands at the same k space location which is equal to the electronic one only for a direct bandgap."
@ Jürgen Weippert
You mean that indirect band gap is not optical band gap???
Thank you very much.
Thank you very much Gabriel Ravanhani Schleder for your reference papers.
My question is based the values of the band gaps after computer simulations.
Thanks again.
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