The use of projection-after-variation double-hybrid density functional theory is proposed and examined as a difference method for the calculation of excited states. The strengths and weaknesses of the proposed method are discussed with particular reference to connections with linear response coupled-cluster theory. Vertical excitation energies are computed for the 28 molecule benchmark of Schreiber and co-workers in order to compare how the model performs with linear response coupled-cluster theories and multireference perturbation theory. The findings of this study show that the proposed method can achieve standard deviations in the error of computed vertical excitation energies compared to complete active space second-order perturbation theory of similar size to linear response coupled-cluster theories.
Difference projection-after-variation double-hybrid density functional theory applied to the calculation of vertical excitation energies
Emily M. Kempfer-Robertson, Thomas Dane Pike, Lee M. Thompson; Difference projection-after-variation double-hybrid density functional theory applied to the calculation of vertical excitation energies. J. Chem. Phys. 21 August 2020; 153 (7): 074103. https://doi.org/10.1063/5.0017222
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