Overall, our results prove that aug-cc-pVDZ basis set already gives sufficiently converged results, which justifies its use for pentane and neopentane dimers. Table summarizes the information about the basis sets used for production calculations. The calculations of plane-averaged ∆ρ CCSD-HF (z) have to be done using electron densities represented on a real-space grid in .cube format; therefore, the sufficient numerical precision of data in these files has to be provided. The default .cube printing precision in PySCF is 5 digits after the comma, which was observed to lead to a numerical noise when computing ∆ρ CCSD-HF (z) (Figure ). It was found that this noise increases with increasing basis set cardinality and system size. We revealed that outputting the density to the .cube file with 9 digits precision eliminates the noise, and the source code of PySCF (cubegen.py file) was modified accordingly. This setting was used for all PySCF calculations. For comparison, the default .cube printing precision is 12 digits in Q-Chem and 8 digits in FHI-aims. The cuboid grid spacing was set to 0.1 Bohr to ensure the sufficient sampling of the density.