Halide Ion Micro-Hydration: Structure, Energetics, and Spectroscopy of Small Halide–Water Clusters

28 January 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Replica exchange molecular dynamics simulations and vibrational spectroscopy calculations are performed using halide-water many-body potential energy functions to provide a bottom-up analysis of the structures, energetics, and hydrogen-bonding arrangements in X−(H2O)n=3−6 clusters, with X = F, Cl, Br, and I. Independently of the cluster size, it is found that all four halides prefer surface-type structures in which they occupy one of the vertices in the underlying three-dimensional hydrogen-bond networks. For fluoride-water clusters, this is in contrast with previous reports suggesting that fluoride prefers interior-type arrangements, where the ion is fully hydrated. These differences can be ascribed to the variability in how various molecular models are capable to reproduce the subtle interplay between halide-water and water-water interactions. Our results thus emphasize the importance of a correct representation of individual many-body contributions to the molecular interactions for a quantitative description of halide ion hydration.


ionic clusters
many-body effects
isomeric equilibria
infrared spectroscopy

Supplementary materials



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