Supplementary Material

Supplementary material for the OO RDFs for pure water and slightly acidic water compared with experimental data, the decomposed RDFs of OO pairs from water and acid molecules, the representative solvation patterns for active H3O+ (δ_"min" <0.1 Å), the computed fraction of special pair acid molecules, contour plots of probability distribution for proton transfer between H3O+ and other species, the MSDs for H2O and H3O+ and their decomposed MSDs of the vehicular and structural components.