Theoretical study of valence and Rydberg excited states of benzene revisited

The multireference Moller-Plesset perturbation (MRMP) theory with complete active space self-consistent field (CASSCF) reference functions is applied to the study of the singlet and tripler valence pi-pi* excited states and Rydberg excited states of benzene in the ultraviolet region. The overall accuracy of MRMP is surprisingly high. The average deviations of the excitation energies from the available experimental values are 0.1 eV for the valence excited slates and 0.15 eV for the Rydberg states. A comparison is made with recent results of single reference-based methods. It is concluded that MRMP is able to describe satisfactorily excited states with a double excitation character, while single reference-based methods are not. (C) 1998 Elsevier Science B.V. All rights reserved.