Hydration structure and dynamics of K+ and Ca2+ in aqueous solution: Comparison of conventional QM/MM and ONIOM-XS MD simulations

Molecular dynamics (MD) simulations based on the conventional QM/MM scheme and ONIOM-XS method have been performed to investigate structural and dynamical properties of K+ and Ca2+ in water. Regarding the detailed analyses of the ONIOM-XS MD trajectories, the average hydration numbers for K+ and Ca2+ were found to be 6.3 and 7.6, respectively, compared with the corresponding values of 7.0 and 7.8 derived by the conventional QM/MM simulations. Together with the significant difference found in the comparison of the dynamics details, the ONIOM-XS method clearly shows its capability in predicting more reliable detailed knowledge of these hydrated ions.