The asymptotic atomic parameters (charges, multipoles, isotropic polarizabilities, and dispersion coefficients) were all computed using the TD-DFT and the ISA-pol methods implemented in Chem 6.8 and CamCASP 6.0. Fluctuating charges and 𝐶 6 coefficients were calculated at different water geometries, and were fitted to a linear model depending on both the O-H bond lengths and the HOH bond angles (see Figure for the quality of the fitting). Other atomic parameters were computed at experimental equilibrium geometry (with OH bond length set to be 0.975 Å and HOH bond angle set to be 104.5 degrees) and were kept fixed throughout the study. The atomic parameters were calculated using asymptotically corrected PBE0 functional and aug-cc-pVQZ basis set.