Benchmarking CASPT3 Vertical Excitation Energies

Martial Boggio-Pasqua (1) , Denis Jacquemin (2) , Pierre-Francois Loos (3)

1 PTC - Photochimie théorique et computationnelle (LCPQ)
2 CEISAM - Chimie Et Interdisciplinarité : Synthèse, Analyse, Modélisation
3 GMO - Groupe THEO (LCPQ)

Based on 280 reference vertical transition energies of various natures (singlet, triplet, valence, Rydberg, n → π * , π → π * , and double excitations) extracted from the QUEST database, we assess the accuracy of third-order multireference perturbation theory, CASPT3, in the context of molecular excited states. When one applies the disputable ionizationpotential-electron-affinity (IPEA) shift, we show that CASPT3 provides a similar accuracy as its second-order counterpart, CASPT2, with the same mean absolute error of 0.11 eV. However, as already reported, we also observe that the accuracy of CASPT3 is almost insensitive to the IPEA shift, irrespective of the transition type and system size, with a small reduction of the mean absolute error to 0.09 eV when the IPEA shift is switched off.

Domaines: Chimie théorique et/ou physique

Martial Boggio-Pasqua, Denis Jacquemin, Pierre-Francois Loos. Benchmarking CASPT3 Vertical Excitation Energies. Journal of Chemical Physics, 2022, 157 (1), pp.014103. ⟨10.1063/5.0095887⟩. ⟨hal-03641092⟩