H ₂ X100: A Gold-Standard CCSD(T)/CBS Benchmark Dataset of Binding Energies, Structures, and Harmonic Frequencies for (H ₂ X) <i> _n </i> , X = S, Se, Te, <i>n</i> = 2–4, and Assessment of Lower-Scaling Density Functional Theory Methods

We constructed a benchmark dataset (H 2 X100) of 100 CCSD(T)/Complete Basis Set (CBS) binding energies for the (H 2 X) n, X = S, Se, Te, n = 2–4 clusters, and additional CCSD(T)-quality structures and harmonic vibrational frequencies for 12 unique homodimer minima, containing a mix of the hydrogen and chalcogen bonding motifs. Using the new H 2 X100 dataset, we assessed the performance of 17 density functionals across the rungs of Jacob’s ladder, with and without dispersion corrections, spanning the GGA, mGGA, GH-GGA, GH-mGGA, RSH-GGA, and RSH-mGGA groupings. The r 2 SCAN-D4, B97M-rV, and ωB97M-V functionals provide the best agreement with the CCSD(T) benchmarks and can be used in studies of larger ensembles of these systems, including simulations of their condensed phases.