For the methane dimer, we performed a cross-validation of the PySCF results with Q-Chem(v.6.1) , and the perfect agreement was obtained between the two codes (Figure ), ensuring the reproducibility of our results. In addition, we examined basis set convergence of the CCSD-HF density differences by performing calculations with aug-cc-pVXZ basis sets, where X = D, T, Q for methane dimer and X = D, T for ethene and ethene-pentane dimers (Figure ). The observed variations are rather small in all three cases. In methane, TZ basis gives practically the same result as QZ, while DZ only slightly overpolarizes the dimer. For ethene and ethene-pentane dimer, DZ basis also shows the close agreement with TZ, which was the largest affordable therein.