Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: POSTERS Polymerphysics

CPP 34.12: Poster

Donnerstag, 28. Februar 2008, 17:00–19:30, Poster A

Structure and thermodynamics of concentrated electrolyte solutions — •Immanuel Kalcher and Joachim Dzubiella — Physics Department, TU Munich

Concentrated electrolytes are a substantial component of many molecular systems, e.g. in cell biology, nanofluidics, or clays. The prediction of their equilibrium structure and thermodynamics in bulk and confinement remains a difficult task. We address this challenge by performing extensive explicit-water molecular dynamics (MD) computer simulations of electrolytes for a wide range of salt species and concentrations (<6M). The bulk ion-ion radial distribution functions (rdfs) are calculated and then used as input in statistical mechanics approaches to predict macroscopic thermodynamics and the inhomogeneous electrolyte structure in confinement. Here we utilize the interesting observation that the water-induced short-ranged structure of the bulk electrolyte is only weakly dependent on salt concentration. By applying a simple Debye-Hueckel approach with a concentration dependent permittivity we show that the different radial distribution functions can be mapped onto each other by separating the short and long range contributions. This mapping enables us to reproduce the experimental osmotic pressures of electrolyte solutions fairly well over a range of 0-3 mol with the knowledge of only two accurate bulk rdfs. Furthermore, strong structural inhomogeneities are observed in MD simulations of concentrated electrolytes in nanometer-sized confinement and are compared to solutions of Poisson-Boltzmann based approaches.