(145d) Molecular Simulation of Organic Electrolyte Solutions

Molecular Simulation of Organic Electrolyte Solutions

Maximilian Kohns, Steffen Reiser, Martin Horsch, Hans Hasse

Laboratory of Engineering Thermodynamics (LTD), University of Kaiserslautern, Germany

Electrolyte solutions play an important role in many industrial processes. In the present work, we apply molecular simulation based on classical force fields with explicit solvent models to determine thermodynamic and structural properties of organic electrolyte solutions. Furthermore, the density of organic electrolyte solutions is studied experimentally. The focus of this work is on methanolic and ethanolic alkali halide salt solutions. The ion and solvent force fields are taken from previous work of our group. The ions are modeled as one Lennard-Jones (LJ) site with a point charge of ±1e in its center of mass [1,2]. Their force fields were optimized for describing basic thermodynamic data of aqueous solutions. The molecular models of the organic solvents methanol and ethanol consist of two and three LJ sites, respectively, and three partial charges to model both polarity and hydrogen bonding [3,4,5]. These models were adjusted to the vapor-liquid equilibrium of the pure component. The simulations were performed with the molecular simulation program ms2 [6]. The long range electrostatic interactions were considered by Ewald summation.

In the present work, basic thermodynamic properties of organic electrolyte solutions with the solvents methanol and ethanol are predicted by molecular simulation. All combinations of alkali cations and halide anions that are soluble in methanol and ethanol, respectively, are considered. The Lorentz-Berthelot combining rule is used for modeling the unlike LJ interactions between the ions and the solvent molecules. No adjustments to data for electrolytes in organic solvents are made. The predictions of the reduced liquid solution density from molecular simulation are in excellent agreement with experimental data, which are measured in the present work. This holds for all studied temperatures. Furthermore, structural properties like the radial distribution function of the solvent molecules around the ions and transport properties like the self-diffusion coefficient and the electric conductivity of the organic electrolyte solutions are investigated.

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[2] S. Reiser, S. Deublein, J. Vrabec, H. Hasse, J. Chem. Phys. 140 (2014) 044504.

[3] T. Schnabel, J. Vrabec, H. Hasse, Fluid Phase Equilib. 239 (2006) 125-126.

[4] T. Schnabel, A. Srivastava, J. Vrabec, H. Hasse, J. Phys. Chem. B 111 (2007) 9871-9878.

[5] S. Reiser, N. McCann, M. Horsch, H. Hasse, J. Supercrit. Fluids 68 (2012) 94-103.

[6] C. W. Glass, S. Reiser, G. Rutkai, S. Deublein, A. Köster, G. Guevara-Carrion, A. Wafai, M. Horsch, M. Bernreuther, T. Windmann, H. Hasse, J. Vrabec, Comput. Phys. Commun. 185 (2014) 3302-3306.