Figure : Timing data for XSAPT + aiD3/hp-TZVPP calculations on a C60@C60H28 complex that is shown (4,592 total basis functions), running on 28 processors (Dell Intel Xeon E5-2680 v4). The total time is broken down into three color-coded steps: the XPol dual SCF procedure (in red), pseudocanonicalization to prepare the dimer basis (in blue), and the SAPT steps (in green). Charge derivatives ∂qa/P A µν are required in all three steps and the time to evaluate them is indicated in purple. Improvements in Gram-Schmidt orthogonalization (timings in orange) reflect better parallelization beginning with Q-Chem v. 6.0. Reprinted from Ref. 41; copyright 2019 American Institute of Physics.