All calculations in this work were done using the ORCA quantum chemistry package (versions 4.21, 5.0.1, 5.0.2 and 5.0.3). The Ahlrichs-type def2-nZVPP family of basis sets 87 was used, with the default def2-ECP effective core potentials for the systems containing molybdenum and tungsten. The resolution of the identity approximation for Coulomb integrals (RI-J) was used for Generalized Gradient Approximation (GGA), meta-GGA and meta-NGA (Nonseparable Gradient Approximation) functionals, while RI-J with the chain of spheres approximation for exchange integrals (RIJCOSX) was used for the hybrid and double-hybrid functionals, as well as the Hartree-Fock steps of MP2 and Coupled Cluster calculations. MP2 steps-including in double hybrids-and Coupled Cluster calculations were sped up with the RI-C approximation and used ORCA's default frozen core settings. These approximations were used with the def2/J 92 and def2-nZVPP/C 93 auxiliary basis sets and the "GridXS2" setting for RIJCOSX. Most calculations were done with the default grids and self-consistent-field (SCF) convergence thresholds.