A simple rigid three-site model for methanol compatible with the simple point charge ͑SPC͒ water and the GROMOS96 force field is parametrized and tested. The influence of different force-field parameters, such as the methanol geometry and the charge distribution on several properties calculated by molecular dynamics is investigated. In particular an attempt was made to obtain good agreement with experimental data for the static dielectric constant and the mixing enthalpy with water. The model is compared to other methanol models from the literature in terms of the ability to reproduce a range of experimental properties.

We report a theoretical study on the liquid−liquid interfacial behavior of the species involved in the extraction of Cs+ by a calix[4]arene-crown6 ionophore (L):  the free Cs+ Pic- and Cs+ Cl- salts, the LCs+ and LCs+ Pic- complexes, and uncomplexed L. Based on molecular dynamics simulations, we calculated the free energies changes for migration from the interface into the aqueous and the organic phases, respectively. For free L and for the LCs+ complex, with or without Pic- counterion, an energy minimum is found close to the interface, on the chloroform side, showing that these species behave as surfactants. This contrasts with the uncomplexed Cs+, which diffuses spontaneously from the interface to water and displays no energy minimum. A remarkable counterion effect is found with Pic- which displays a high affinity for the interface, while Cl- prefers the bulk aqueous phase. The questions of ion extraction by ionophores, counterions, concentration and synergistic effects in assisted cation transfer through the liquid−liquid interface between immiscible liquids are discussed from the interfacial point of view.

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