Assessment of dynamic properties of water around a monovalent ion: A classical molecular dynamics simulation study

Mobility change of water molecules in ionic solutions has been a long standing issue in the field of spectroscopy; however, the molecular mechanism is still controversial. To address this issue, molecular dynamics (MD) simulations are considered to be useful tools because MD simulations can provide deeper insights into dynamics of water molecules at the atomic level, compensating for the limitation of experimental observations. However, the reliability of these simulations is significant and strongly dependent on the molecular models employed. We examined the reproduction of the dynamics of water molecules under the influence of alkali and halide monovalent ions by using the framework of classical MD simulations. Conventional water models were combined with non-polarizable ion models. The decreased mobility of water molecules was reproduced in our simulations while the increased mobility could not be reproduced. However, from the examined water models, the TIP5P model can be promising to reproduce the experimental results if ion–water interactions are improved.