We now turn to the potential numerical errors introduced by the density fitting approximations used. In order to verify the validity of our results we have to benchmark the errors on absolute and relative energies. Therefore, we first employ size increasing clusters of the formic acid molecule ranging from one up to a cluster of four molecules. The obtained results are displayed in Fig. . The absolute error introduced by the density fitting scales very low in regards to the overall system size. For the formic acid monomer the absolute error is only 0.04 kJ mol 1 and increases only slightly up to 0.12 kJ mol 1 for the formic acid tetramer. The absolute error of the trimer, which is slightly bigger than its deprotonated counterpart, is only 0.09 kJ mol . In order to also assess the impact of the density fitting on the relative energies we analysed the di↵erences in the energies for density-fitted B3LYP-D3(BJ) and regular B3LYP-D3(BJ) results. The obtained energies are shown in Tab. S 1. The overall root mean square deviation between the relative energies is only 0.001 kJ mol . Such a minor error on relative energies is widely expected. In general, the error introduced by density fitting approximations, especially for relative energies, seems negligible. The next system we would like to revisit with NEO-DFT is the diphenyl ether-tert-butyl alcohol complex. The complex was investigated with a multi-spectroscopic approach by Bernhard et al. This included FTIR spectroscopy, IR/UV spectroscopy and chirp pulse Fourier transform microwave spectroscopy together with a broad mixture of theoretical approaches going from B3LYP-D3(BJ), over MP2 and CC2 calculations to symmetry adapted perturbation theory. Experimentally the results point in the direction that the OH-O bound dimer is slightly more stable than the OH-⇡ bound isomer. This was derived based on almost similar abundance resulting from the FTIR spectra from the helium expansion, the higher abundance of the OH-O isomer in the mass-and isomer-selective IR/R2PI spectra in neon expansion supported by the broadband rotational spectra in helium and neon. In general the experimental preference towards the OH-O bound dimer was estimated to be in the energy range of 0 1 kJ mol . Theoretical results however vary largely for the methods employed in their analysis. We recomputed the most stable isomers, predicted by the previous work, with regular B3LYP-D3(BJ) and NEO-B3LYP-D3(BJ). The obtained results are shown in Fig. . In agreement with prior B3LYP-D3(BJ) results the most stable isomer is predicted to be OH-⇡ bound. It is a rather small energetic gap to the OH-O bound isomer with only 0.23 kJ mol 1 , which would be in agreement with the experimental observation of both species. Moreover, the second determined OH-⇡ 0 structure is energetically 0.33 kJ mol 1 higher than the OH-⇡ structure which again is in agreement with experiment. By rotational spectroscopy the OH-⇡ structure was assigned to be the observed species instead of OH-⇡ 0 . 25 However, B3LYP-D3(BJ) predicts the OH-⇡ bound dimer to be energetically preferred over the OH-O bound dimer which is against the experimental conclusions. By employing NEO-B3LYP-D3(BJ) the ordering of the PES changes. The global minimum obtained from the multicomponent PES is the OH-O bound dimer, whereas the OH-⇡ bound dimer is energetically 0.97 kJ mol 1 higher in energy. Both observations are in agreement with the experimentally derived balance of the OH-O and OH-⇡ bound dimer. In addition, the OH-⇡ 0 structure is energetically 0.20 kJ mol 1 higher as the OH-⇡ structure, which agrees with the rotational spectroscopy experiment. Overall, the results obtained by NEO-B3LYP-D3(BJ) agree in all points with the experimental observations with minimal added computational e↵ort.