Unrestricted Hartree-Fock (UHF) wave functions with spin contamination are usually poor zero-order approximations for second-order Moller-Plesset perturbation theory (MP2). Orbital-optimized second-order perturbation theory (OOMP2) tackle this problem by using approximate Brueckner orbitals. In OOMP2 the orbitals are optimized in the presence of the mean-field energy plus the second-order many-body correlation energy. This method improves the description of geometries, vibrational frequencies, and relative energies. In this contribution, we present an extension of the OOMP2 method to excited states. We report test calculations for closed-shell systems and open- shell doublet radicals. The performance of method is compared with other second-order methods for excitation energies such as the approximate coupled-cluster singles and doubles model (CC2), configuration interaction with doubles corrections (CIS(D)), and the algebraic diagrammatic construction through second order (ADC(2)).

Excited states for orbital-optimized second-order perturbation theory

253rd National Meeting (2017)

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