Effects of Hydrogen Bond Networks on Viscosity in\nAqueous Solutions

In\naqueous solutions, the impact of ions on hydrogen bond networks\nplays a crucial role in transport properties. We used molecular dynamics\nsimulations to explain how ions affect viscosity through structural\nchanges. We developed a quantitative model to describe the effect\nof ions on viscosity. The model comprises two parts: the addition\nof ions alters hydrogen bond networks, and changes in hydrogen bond\nnetworks exponentially lead to changes in viscosity. The influence\nof ions on hydrogen bond networks involves the following mechanisms:\nfirst, ions can disrupt the tetrahedral structures within the first\nsolvation shell into three-coordinated structures through substitution;\nsecond, structural changes within the first shells affect the global\nhydrogen bond network through electrostatic forces and the hindrance\nof ionic volumes. By analyzing the mechanisms of how hydrogen bond\nnetworks determine viscosity through the decomposition of viscosity,\nwe found that the proportion of potential viscosity in aqueous solutions\nprimarily increases due to the enhancement of non-hydrogen bonding\ninteractions, and the proportion of hydrogen bonding viscosity decreases\naccordingly. Our results demonstrate that hydrogen bond networks are\ncrucial for describing the changes in transport phenomena affected\nby external factors.