“Structure Breaking” Effect of Hydrated Cs

Structural and dynamical properties of the hydrated Cs+ ion have been investigated by performing ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations at different quantum mechanical levels (HF, B3LYP and BP86). The first shell coordination number was found to be ∼8 in the HF and ∼9 in the B3LYP and BP86 case and several other structural parameters such as angular distribution functions, radial distribution functions, and tilt- and θ-angle distributions allowed to fully characterize the hydration structure of the Cs+ ion. Velocity autocorrelation functions were used to calculate librational and vibrational motions, ion−ligand motions, as well as reorientation times. The strong “structure breaking” effect of Cs+ can be interpreted on the basis of different dynamical parameters such as accelerated water reorientation, mean ligand residence time, and the number of ligand exchange processes.