How To Interpret ricc2 Excitation Energy Calculation Output?

[mbeyhan]

Hi,

I've done ricc2 singlet state excitation energy calculations including the excited state properties for this molecule called daidzein, which is a member of isoflavones. I've done the same type of calculations using DFT too. The thing is with DFT I get for the lowest excited states, excitations such as HOMO to LUMO (from the 66th orbital to 67th), as expected. However, in ricc2 output I get for the lowest excitation, from the 61th orbital to 75th, and for the following excitations, from 66th to 78th, and such. On the other hand numerically, the excitation energies are consistent with I get with TDDFT. I am thus a bit confused about how to interpret the ricc2 output in terms of orbitals involving in excitations. Could you please help?

Thanks,

Maya

[christof.haettig]

Hi Maya,
the numbering of the orbitals is in both programs identical and corresponds to order of the orbitals in dscf and ridft. Note, however, that (due to the somewhat different physical meaning of the orbital energies) the order of the MOs in dscf and ridft is, in particular for virtual orbitals, at the DFT level quite different from that at the Hartree-Fock level..
Christof