QM/MM MD simulations of iodide ion (I(-)) in aqueous solution: a delicate balance between ion-water and water-water H-bond interactions.

The characteristics of an iodide ion (I(-)) in aqueous solution were investigated by means of HF/MM and B3LYP/MM molecular dynamics simulations, in which the ion and its surrounding water molecules were treated at HF and B3LYP levels using the LANL2DZdp and D95 V+ basis sets for I(-) and water, respectively. According to both the HF/MM and B3LYP/MM results, the ion-water interactions are relatively weak, compared to the water-water hydrogen bonds, thus causing an unstructured nature of the hydration shell. Comparing the HF and B3LYP treatments for the description of this hydrated ion, the overestimation of the ion-water hydrogen-bond strength by the B3LYP method is recognizable, yielding a remarkably more compact and too rigid ion-water complex.