In this contribution the development, definition and selected applications of a new force field (FF) for metal‐organic frameworks MOF‐FF is presented. MOF‐FF is fully flexible and is parameterized in a systematic and consistent fashion from first principles reference data. It can be used for a variety of different MOF‐families and in particular – due to the reparametrization of a variety of organic linkers – also to explore isoreticular series of systems. The history of the development, leading to the final definition of MOF‐FF is reviewed along with the application of the previous incarnations of the FF. In addition, the parametrization approach is explained in a tutorial fashion. The currently parametrized set of inorganic building blocks is constantly extended.
Formate models of currently covered inorganic building blocks.
In this study we present the results of a first principles molecular dynamics simulation of a single 1-ethyl-3-methyl-imidazolium chloride [C(2)C(1)im][Cl] ion pair dissolved in 60 water molecules. We observe a preference of the in plane chloride coordination with respect to the cation ring plane as compared to the energetic slightly more demanding on top coordination. Evaluation of the different radial distribution functions demonstrates that the structure of the hydration shell around the ion pair differs significantly from bulk water and that no true ion pair dissociation in terms of completely autonomous solvation shells takes place on the timescale of the simulation. In addition, dipole moment distributions of the solvent in distinct solvation shells around different functional parts of the [C(2)C(1)im][Cl] ion pair are calculated from maximally localized Wannier functions. The analysis of these distributions gives evidence for a depolarization of water molecules close to the hydrophobic parts of the cation as well as close to the anion. Examination of the angular distribution of different OH(H(2)O)-X angles in turn shows a linear coordination of chloride accompanied by a tangential orientation of water molecules around the hydrophobic groups, being a typical feature of hydrophobic hydration. Based on these orientational aspects, a structural model for the obvious preference of ion pair association is developed, which justifies the associating behavior of solvated [C(2)C(1)im][Cl] ions in terms of an energetically favorable interface between the solvation shells of the anion and the hydrophobic parts of the cation.
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