title: Is the Bethe-Salpeter Formalism Accurate for Excitation Energies? Comparisons with TD-DFT, CASPT2, and EOM-CCSD.
abstract: Developing ab initio approaches able to provide accurate excited-state energies at a reasonable computational cost is one of the biggest challenges in theoretical chemistry. In that framework, the Bethe-Salpeter equation approach, combined with the GW exchange-correlation self-energy, which maintains the same scaling with system size as TD-DFT, has recently been the focus of a rapidly increasing number of applications in molecular chemistry. Using a recently proposed set encompassing excitation energies of many kinds [J. Phys. Chem. Lett. 2016, 7, 586-591], we investigate here the performances of BSE/GW. We compare these results to CASPT2, EOM-CCSD, and TD-DFT data and show that BSE/GW provides an accuracy comparable to the two wave function methods. It is particularly remarkable that the BSE/GW is equally efficient for valence, Rydberg, and charge-transfer excitations. In contrast, it provides a poor description of triplet excited states, for which EOM-CCSD and CASPT2 clearly outperform BSE/GW. This contribution therefore supports the use of the Bethe-Salpeter approach for spin-conserving transitions.
authors.affiliation: Laboratoire CEISAM - UMR CNRS 6230, Université de Nantes , 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.|Institut Universitaire de France , 1 rue Descartes, 75231 Paris Cedex 5, France.
authors.forename: Denis
authors.identifier: http://orcid.org/0000-0002-4217-0708
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: Univ. Grenobles Alpes , CEA, INAC-MEM, L_Sim, F-38000 Grenoble, France.|Univ. Grenoble Alpes , Inst NEEL, F-38042 Grenoble, France.
authors.forename: Ivan
authors.identifier: http://orcid.org/0000-0003-4713-1174
authors.initials: I
authors.lastname: Duchemin
authors.affiliation: Univ. Grenoble Alpes , Inst NEEL, F-38042 Grenoble, France.|CNRS, Inst NEEL, F-38042 Grenoble, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Blase