LAUSR

Abstract We investigated structure properties of structure-making salts (LiCl, NaCl, and NaBr) and structure-breaking salts (KCl and KBr) solutions of 0.5 M to 4 M using TIP4P/2005 water model and OPLS ionic force fields. The viscosity results show a good trend with experimental values for all salts. For the water structure, the O O number decreased with increasing salt concentrations but is independent of the salt types. There is an extra shoulder (Cl-O/LiCl) or no obvious low-point at the first minimum point of anion‑oxygen RDF patterns (Cl-O/NaCl and Br-O/NaBr) while two structure-breaking salts show a normal minimum point (Cl-O/KCl and Br-O/KBr). Additionally, we observed that the ratio (R12) of primary and second shell cation-anion numbers showed a similar trend as the viscosity behaves with increasing salt concentration. For structure-making salts, values of R12 increased with increasing salt concentrations while R12 values of structure-breaking salts slightly decreased with concentration. These observations may indicate that the change in viscosity is due to the disturbance of cation-anion contact hydration pairs, not the free water hydrogen network.