Orbital energy

{
  "id": "MLC-T-CHM-008297",
  "term": "Orbital energy",
  "field": "Chemistry",
  "definition": "The eigenvalue of the one-electron effective Hamiltonian for a given orbital, giving the energy of an electron in that orbital within the mean field of the nuclei and all the other electrons. In Hartree-Fock theory the negative of an occupied orbital energy approximates the energy needed to remove that electron, a relation known as Koopmans' theorem. It ignores orbital relaxation and electron correlation, so it typically differs from measured ionization energies by about an electronvolt.",
  "subject": "Physical and Biophysical Chemistry",
  "references": [
    "Green Book, 2nd ed., p. 18 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/orbital-energy/"
}