Chalcogen bonds: Hierarchical ab initio benchmark and density functional theory performance study

We have performed a hierarchical ab initio benchmark and DFT performance study of D(2)Ch•••A(−) chalcogen bonds (Ch = S, Se; D, A = F, Cl). The ab initio benchmark study is based on a series of ZORA‐relativistic quantum chemical methods [HF, MP2, CCSD, CCSD(T)], and all‐electron relativistically contracted variants of Karlsruhe basis sets (ZORA‐def2‐SVP, ZORA‐def2‐TZVPP, ZORA‐def2‐QZVPP) with and without diffuse functions. The highest‐level ZORA‐CCSD(T)/ma‐ZORA‐def2‐QZVPP counterpoise‐corrected complexation energies (ΔE (CPC)) are converged within 1.1–3.4 kcal mol(−1) and 1.5–3.1 kcal mol(−1) with respect to the method and basis set, respectively. Next, we used the ZORA‐CCSD(T)/ma‐ZORA‐def2‐QZVPP (ΔE (CPC)) as reference data for analyzing the performance of 13 different ZORA‐relativistic DFT approaches in combination with the Slater‐type QZ4P basis set. We find that the three‐best performing functionals are M06‐2X, B3LYP, and M06, with mean absolute errors (MAE) of 4.1, 4.2, and 4.3 kcal mol(−1), respectively. The MAE for BLYP‐D3(BJ) and PBE amount to 8.5 and 9.3 kcal mol(−1), respectively.