Organodichalcogenide Structure and Stability: Hierarchical Ab Initio Benchmark and DFT Performance Study

ABSTRACT We conducted a double‐hierarchical ab initio benchmark and DFT performance study of the organodichalcogenide bonding motif CH 3 Ch 1 Ch 2 (O) n CH 3 with Ch 1 , Ch 2  = S, Se and n  = 0, 1, 2. The organodichalcogenide model systems were optimized at ZORA‐CCSD(T)/ma‐ZORA‐def2‐TZVPP. Our ab initio benchmark involved a hierarchical series of all‐electron relativistically contracted variants of the Karlsruhe basis sets (ZORA‐def2‐SVP, ZORA‐def2‐TZVPP, ZORA‐def2‐QZVPP), both with and without diffuse functions (ma‐basis set), in conjunction with a hierarchical series of ZORA‐relativistic quantum chemical methods [HF, MP2, CCSD, and CCSD(T)]. Counterpoise correction was applied to account for the basis set superposition error (BSSE). We assessed the performance of 33 ZORA‐relativistic DFT functionals (ZORA‐[XC functional]/TZ2P//ZORA‐[XC functional]/TZ2P) against our benchmark energies and found that M06 and MN15 furnish accurate geometries and bond energies within a mean absolute error of 1.2 kcal mol −1 relative to our best ab initio reference data.