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We present here the implementation of a self-consistent approach to the calculation of excitation energies within regular Kohn-Sham density functional theory. The method is based on the n-order constricted variational density functional theory (CV(n)-DFT) [T. Ziegler, M. Seth, M. Krykunov, J. Autschbach, and F. Wang, J. Chem. Phys. 130, 154102 (2009)] and its self-consistent formulation (SCF-CV(∞)-DFT) [J. Cullen, M. Krykunov, and T. Ziegler, Chem. Phys. 391, 11 (2011)]. A full account is given of the way in which SCF-CV(∞)-DFT is implemented. The SCF-CV(∞)-DFT scheme is further applied to transitions from occupied π orbitals to virtual π(∗) orbitals. The same series of transitions has been studied previously by high-level ab initio methods. We compare here the performance of SCF-CV(∞)-DFT to that of time dependent density functional theory (TD-DFT), CV(n)-DFT and ΔSCF-DFT, with the ab initio results as a benchmark standard. It is finally demonstrated how adiabatic TD-DFT and ΔSCF-DFT are related through different approximations to SCF-CV(∞)-DFT.

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A modified ansatz for explicitly correlated coupled-cluster wave functions that is suitable for response theory Implementation of transition moments between excited states in the approximate coupled-cluster singles and doubles model Explicitly correlated coupled-cluster singles and doubles method based on complete diagrammatic equations From the diagrammatic construction of the full coupled-cluster theory of all single and double excitations, a linearized theory, a direct configuration interaction theory (CISD). a CEPA-like theory, and a linked singles and doubles (LSD) theory are separated. These theories are then compared with one another. with the results from full fourth-order perturbation theory, and with exact results when available. The LSD model, corresponding to the removal of unlinked terms of the CISD, and its spin adapted version, appear most accurate in Pariser-Parr-Pople studies where the exact numbers are known. Examples within the localized bond model are given indicating that this model is also the most successful of those examined in generating not only the basis set correlation, but the necessary delocalization and polarization required to correct for the zeroth-order local description.4088