Based on a systematic investigation of trajectories of ab initio quantum mechanical/molecular mechanical simulations of numerous cations in water a standardized procedure for the evaluation of mean ligand residence times is proposed. For the characterization of reactivity and structure-breaking/structure-forming properties of the ions a measure is derived from the mean residence times calculated with different time limits. It is shown that ab initio simulations can provide much insight into ultrafast dynamics that are presently not easily accessible by experiment.

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Articles you may be interested inDynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region Structural and dynamical properties of Co(III) in aqueous solution: Ab initio quantum mechanical/molecular mechanical molecular dynamics simulation Copper͑II͒ was used as a model system to investigate the relevance of including the full second hydration shell in ab initio treatment while describing hydrated ions in hybrid quantum mechanical/ molecular mechanical molecular dynamics ͑QM/MM MD͒ simulations. Three different simulation techniques were applied ͑Hartree-Fock, B3LYP, and resolution of the identity density functional theory͒ to find a good compromise between accuracy and simulation speed. To discuss details of the hydration structure radial distribution functions, coordination number distributions and various angular distributions have been used. Dynamical properties such as vibrational motions of water molecules and ion-oxygen stretching motions were investigated using approximative normal coordinate analyses. QM/MM MD simulations offer a detailed time picture of the dynamic Jahn-Teller effect of Cu 2ϩ showing short-term as well as long-term distortions to occur within Ͻ200 fs and 2-3 ps. The results prove that for transition metal ions such as Cu 2ϩ the inclusion of the second shell into the ab initio treated region can be of decisive importance for obtaining accurate results and that such simulations can offer new insights into chemical dynamics on the picosecond scale.