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Low-Cost Molecular Excited States from a State-Averaged Resonating Hartree-Fock Approach

submitted on 20.03.2019, 18:06 and posted on 21.03.2019, 14:30 by Jacob Nite, Carlos A. Jimenez-Hoyos
Quantum chemistry methods that describe excited states on the same footing as the ground state are generally scarce. In previous work, Gill et al. (J. Phys. Chem. A 112, 13164 (2008)) and later Sundstrom and Head-Gordon (J. Chem. Phys. 140, 114103 (2014)) considered excited states resulting from a non-orthogonal configuration interaction (NOCI) on stationary solutions of the Hartree–Fock equations. We build upon those contributions and present the state-averaged resonating Hartree–Fock (sa-ResHF) method, which differs from NOCI in that spin-projection and orbital relaxation effects are incorporated from the onset. Our results in a set of small molecules (alanine, formaldehyde, acetaldehyde, acetone, formamide, and ethylene) suggest that sa-ResHF excitation energies are a notable improvement over configuration interaction singles (CIS), at a mean-field computational cost. The orbital relaxation in sa-ResHF, in the presence of a spin-projection operator, generally results in excitation energies that are closer to the experimental values than the corresponding NOCI ones.


Email Address of Submitting Author


Wesleyan University


United States of America

ORCID For Submitting Author


Declaration of Conflict of Interest

The authors declare that they have no conflict of interest.


Read the published paper

in Journal of Chemical Theory and Computation