Development of Molecular Simulation Methods to Compute Interfacial Properties of Electrolytes

Jeffrey Errington of the State University of New York at Buffalo is supported by an award from the Theory, Models and Computational Methods program in the Chemistry division to carry out the development of molecular simulation methods to compute interfacial properties of electrolytes. The award is co-funded by the Interfacial Processes and Thermodynamics program in CBET. The PI and his research group develop free energy-based methods to study interfacial properties of a system via connection to rigorous thermodynamic relationships. The group pursues two approaches. The first technique focuses on the evaluation of contact angles and solid-fluid interfacial tensions via determination of the surface density dependence of the so-called surface excess free energy of a system. The free energy approach has a number of advantages over the commonly-used nanodroplet route to the contact angle. The second method focuses on the determination of liquid-vapor surface tensions via area sampling techniques, which deduce the interfacial tension via measurement of the change in system free energy upon variation of the interfacial area. The research involves extending the use of transition matrix Monte Carlo methods to compute free energies to the study of electrolytes. Numerous technologies (e.g. batteries, fuel cells) contain an electrolytic fluid in contact with one or more solid surfaces. In many cases the performance of such devices is influenced significantly by the properties of the electrolyte-solid interface. It follows that the design of these applications benefits from fundamental knowledge regarding the relationship between microscopic substrate-fluid and fluid-fluid interactions within a system and the macroscopic properties it exhibits. Information of this type provides insight into how the chemistry and/or structure of a substrate can be tuned to obtain a desired behavior. Both undergraduates and graduate students are involved in this research. The PI has initiated an outreach program to middle school students that focuses on lithium-ion batteries and how they work.