Benchmarking Post-Hartree–Fock Methods To Describe the Nonlinear Optical Properties of Polymethines: An Investigation of the Accuracy of Algebraic Diagrammatic Construction (ADC) Approaches

Abstract
Third-order nonlinear optical (NLO) properties of polymethine dyes have been widely studied for applications such as all-optical switching. However, the limited accuracy of the current computational methodologies has prevented a comprehensive understanding of the nature of the lowest excited states and their influence on the molecular optical and NLO properties. Here, attention is paid to the lowest excited-state energies and their energetic ratio, as these characteristics impact the figure-of-merit for all-optical switching. For a series of model polymethines, we compare several algebraic diagrammatic construction (ADC) schemes for the polarization propagator with approximate second-order coupled cluster (CC2) theory, the widely used INDO/MRDCI approach and the symmetry-adapted cluster configuration interaction (SAC-CI) algorithm incorporating singles and doubles linked excitation operators (SAC-CI SD-R). We focus in particular on the ground-to-excited state transition dipole moments and the corresponding state dipole moments, since these quantities are found to be of utmost importance for an effective description of the third-order polarizability γ and two-photon absorption spectra. A sum-overstates expression has been used, which is found to quickly converge. While ADC(3/2) has been found to be the most appropriate method to calculate these properties, CC2 performs poorly.

Citation
Knippenberg S, Gieseking RL, Rehn DR, Mukhopadhyay S, Dreuw A, et al. (2016) Benchmarking Post-Hartree–Fock Methods To Describe the Nonlinear Optical Properties of Polymethines: An Investigation of the Accuracy of Algebraic Diagrammatic Construction (ADC) Approaches. Journal of Chemical Theory and Computation 12: 5465–5476. Available: http://dx.doi.org/10.1021/acs.jctc.6b00615.

Acknowledgements
S.K. is grateful to the Georgia Institute of Technology for their hospitality in Fall 2012. The authors thank Dr. Paul Winget for computational assistance.

Publisher
American Chemical Society (ACS)

Journal
Journal of Chemical Theory and Computation

DOI
10.1021/acs.jctc.6b00615

Additional Links
http://pubs.acs.org/doi/abs/10.1021/acs.jctc.6b00615

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