Figure documents the parallel efficiency of the new RI-SAPT0 code, running on a single compute node using OpenMP parallelization. Scaling is reasonably good across an entire node and does not vary strongly amongst cc-pVXZ basis sets, at least for the guanine-cytosine base pair that is used as a test system. Parallel efficiencies are considerably improved, relative to the old code, when more than a few processors are used. Memory usage is also improved, enabling cc-pVQZ calculations (1,345 basis functions) that were previously not feasible on our hardware. We next examine parallel efficiencies for XSAPT + ai D3, which has a much different cost profile. For these tests, we have extended upon data for Cl -(H 2 O) n clusters that were published elsewhere, adding new basis sets and updated timings. These Cl -(H 2 O) n clusters were extracted from a molecular dynamics simulation of Cl -(aq), 184 with n = 28.4 ± 2.4 per snapshot, and the data presented in Table are averages across 51 snapshots, treating (H 2 O) n as a single monomer. For Pople basis sets, parallel efficiencies approach or exceed 80% on 26 processors, although they are lower (46-67%) for Karlsruhe basis sets. The difference likely lies in the use of compound ("sp") shells for Pople basis sets, which Q-Chem's integrals code handles efficiently. Although Pople basis sets have fallen out of favor for modern electronic structure calculations (for good reason in certain cases), they can yield high-quality results for DFT calculations if sufficient polarization functions are included, beyond the usual 6-31G(d) or 6-311G(d,p). In the present context, Pople basis sets can reproduce induction energies obtained in much larger Karlsruhe or Dunning basis sets, to an acceptable degree, if additional polarization functions are included. For example, XSAPT + δHF + MBD induction energies computed using the 6-311++G(3df,2pd) basis set exhibit slightly smaller errors, as compared to SAPT2+(3)/aug-cc-pVTZ benchmarks, 151 than when the def2-QZVPD basis set is used. Errors are small in both cases, but the Pople basis set is dramatically more efficient. This is a rather general observation. To see this, we take XSAPT + MBD/def2-TZVPD results as converged and examine interaction energies for Cl -(H 2 O) n computed in other basis sets (Table ). The data indicate that 6-311+G(2df,2p) affords negligible differences as compared to def2-TZVPD but is 4.5× less expensive, when measured in aggregate CPU time, and 6.7× faster in wall time. For rough estimates of ∼ 1 kcal/mol accuracy, even 6-311+G(d,p) can be used and is more than an order of magnitude faster than def2-TZVPD.