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Closed-form expression for excitation energies, given the exact XC functional

Do you consider the exact frequency-dependent XC kernel as part of "the exact XC functional"? And do you allow the use of additional ingredients like two-electron integrals? If both of your ...
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Closed-form expression for excitation energies, given the exact XC functional

No, they cannot be obtained from a DFT calculation. As the first paper I linked in the previous response says, DFT is a ground state theory, and it should not be expected to get excited state ...
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5 votes
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Question on generalised Kohn-Sham "band gap"

The optical band gap is not expected to equal the DFT band gap since excitonic effects are not included. What you are referring to is the fundamental gap. The fundamental gap is related to electron ...
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