Theoretical study of the photoelectron spectra of gaseous Cu3Cl3

Ab initio calculations have been performed to interpret the photoelectron spectrum of gaseous cuprous chloride, Cu3Cl3. Density functional calculations revealed Cu3Cl3 to be a planar cyclic D3h molecule. Koopmans' theorem and two-hole/one-particle calculations with canonical Hartree-Fock orbitals were used to interpret the vertical ionization energies. These were compared with similar calculations using B3LYP Kohn-Sham orbitals. The results confirm the claim by Casida that Kohn-Sham orbitals mimic Dyson orbitals.