Meaning of Koopmans' theorem | Babel Free

Definitions

A theory stating that, in closed-shell Hartree-Fock theory, the first ionization energy of a molecular system is equal to the negative of the orbital energy of the highest occupied molecular orbital (HOMO).

Examples

“There exists another approach to correct the DFT and its related Kohn-Sham Hamiltonian: the Koopmans’ theorem¹¹⁻²². The original Koopmans’ theorem only states that in Hartree-Fock, the first ionization energy is equal to the highest occupied orbital energy if the wave function relaxations are ignored. In the literature¹¹⁻²¹, the terminology “Koopmans’ theorem” was used to indicate the straight-line condition (SLC) of the total energy E(n) as a function of the continuous number of electrons n between two integer points²³.”

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