QTAIM and source function analysis were used to explore the non-covalent bonding in twelve different water clusters (H2O)n obtained by considering n = 2-7 and various geometrical arrangements. A total of seventy-seven Oampersand-flag-changeminus;H⋯O hydrogen bonds (HBs) were identified in the systems under consideration, and the examination of the electron density at the bond critical point (BCP) of these HBs revealed the existence of a great diversity of Oampersand-flag-changeminus;H⋯O interactions. Furthermore, the analysis of quantities, such as |y#x1d449;(y#x1d42b;)|/y#x1d43a;(y#x1d42b;) and y#x1d43b;(y#x1d42b;), allowed a further description of the nature of analogous Oampersand-flag-changeminus;H⋯O interactions within each cluster. In the case of 2-D cyclic clusters, the HBs are nearly equivalent between them. However, significant differences among the Oampersand-flag-changeminus;H⋯O interactions were observed in 3-D clusters. The assessment of the source function (SF) confirmed these findings. Finally, the ability of SF to decompose the electron density (ampersand-flag-changerho;) into atomic contributions allowed the evaluation of the localized or delocalized character of these contributions to ampersand-flag-changerho; at the BCP associated to the different HBs, revealing that weak Oampersand-flag-changeminus;H⋯O interactions have a significant spread of the atomic contributions, whereas strong interactions have more localized atomic contributions. These observations suggest that the nature of the Oampersand-flag-changeminus;H⋯O hydrogen bond in water clusters is determined by the inductive effects originated by the different spatial arrangements of the water molecules in the studied clusters.
