Excited-State Static Polarizabilities: CC3 Reference Values, Wave Function, and TD-DFT Benchmarks

We present a comprehensive benchmark of excited-state polarizabilities for a representative set of more than 40 singlet states from 27 small organic molecules. Reference data were obtained using the high-level coupled-cluster CC3 model in combination with the aug-cc-pVTZ atomic basis set, providing the first systematic data set of excited-state polarizabilities at this level of theory. The studied set includes both valence and Rydberg states, the latter exhibiting significantly larger polarizabilities, reflecting their diffuse character and enhanced sensitivity to external electric fields. The benchmark analysis includes lower-level wave function-based methods, namely, CCSD and CC2, as well as Time-Dependent Density Functional Theory (TD-DFT) with several common density functional approximations (B3LYP, MN15, M06-2X, CAM-B3LYP, and LC-BLYP). The statistical analysis enables the evaluation of the impact of orbital relaxation and highlights method-dependent differences across the different kinds of excited states. The results indicate that CCSD, in both its relaxed and unrelaxed forms, provides the most accurate description of excited-state polarizabilities, closely followed by CC2, which can therefore be generally employed as a computationally efficient yet reliable alternative. Among the TD-DFT functionals, range-separated hybrids─particularly LC-BLYP─perform best, while larger errors are observed for the three evaluated global hybrids.