2.4. Quantum Chemistry Calculations. Calculations were performed using Fragme∩t 26,30 interfaced to Q-Chem v. 6.0. For timing data, calculations were run on 28-core nodes (Dell Intel Xeon E5-2680 v4) using 7 worker processes per node, with each individual Q-Chem calculation employing 4 cores. Supersystem calculations were performed using a single 48-core node (Intel Xeon Platinum 8268). Timings will be reported in terms of aggregate computer time across all processors. The self-consistent field convergence threshold was set to 10 -8 E h for all calculations. Integral screening and shell-pair drop tolerances were both set to 10 -12 a.u., consistent with recommendations for large-molecule calculations using diffuse basis sets. We use the ωB97X-V functional as our target level of theory, as it performs well across a wide range of benchmarks including non-covalent interaction energies for small molecules, where the benchmarks are well established. (For molecules with 100+ atoms, benchmarks are more uncertain. ) Minimally-augmented versions of the Karlsruhe basis sets are used for the ωB97X-V calculations. Diffuse functions can be important for noncovalent interaction energies but minimal augmentation is sufficient for this purpose. The semi-empirical HF-3c model is used to evaluate convergence and all HF-3c calculations use the minimal "MINIX" basis set. Since HF-3c is specifically parameterized for MINIX that basis set will not be mentioned in the discussion that follows, whereas for ωB97X-V we will systematically test the basis-set convergence.