Hartree–Fock and standard density functional theory methods applied to excited states: The case of NO 2

Abstract

It has been shown that energies and geometries of lowest and higher excited states of symmetric molecules can be calculated with reasonable accuracy by Hartree–Fock (HF) and standard (time-independent) density functional theory (DFT) methods. In the example of NO 2, the geometries of 15 excited doublet states in C 2 v symmetry, (1–5) 2A 2, (1–5) 2B 1, and (1–5) 2B 2 were optimized by UHF and DFT (UB3PW91) with a 6-311+G(3df) basis set, all resulting from single excitations with respect to the 2A 1 ground state. Energies and optimized geometries compare well with available literature values. Vertical HF and DFT excitation energies for these states have been compared with multireference configuration interaction and time-dependent DFT values. Examples of DFT optimized doubly and triply excited doublet states are given.