Beyond Explored Functionals: A Computational Journey of Two-Photon Absorption

• Published in: Journal of chemical theory and computation Vol. 20; no. 9; pp. 3879 - 3893
• Main Authors: Elayan, Ismael A., Rib, Laura, A. Mendes, Rodrigo, Brown, Alex
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14-05-2024
• Subjects: Absorption cross sections; Approximation; Coumarin; Density functional theory; Dipole moments; Photon absorption; Photons; Spectroscopy and Excited States
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/acs.jctc.4c00133

We present a thorough investigation into the efficacy of 19 density functional theory (DFT) functionals, relative to RI-CC2 results, for computing two-photon absorption (2PA) cross sections (σ2PA) and key dipole moments (|μ00|, |μ11|, |Δμ|, |μ01|) for a series of coumarin dyes in the gas-phase. The functionals include different categories, including local density approximation (LDA), generalized gradient approximation (GGA), hybrid-GGA (H-GGA), range-separated hybrid-GGA (RSH-GGA), meta-GGA (M-GGA), and hybrid M-GGA (HM-GGA), with 14 of them being subjected to analysis for the first time with respect to predicting σ2PA values. Analysis reveals that functionals integrating both short-range (SR) and long-range (LR) corrections, particularly those within the RSH-GGA and HM-GGA classes, outperform the others. Furthermore, the range-separation approach was found more impactful compared to the varying percentages of Hartree–Fock exchange (HF E x ) within different functionals. The functionals traditionally recommended for 2PA do not appear among the top 9 in our study, which is particularly interesting, as these top-performing functionals have not been previously investigated in this context. This list is dominated by M11, QTP variants, ωB97X, ωB97X-V, and M06-2X, surpassing the performance of other functionals, including the commonly used CAM-B3LYP.