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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