Theory and simulations of ionic liquids and molten salts: From Bulk to Interfaces

This dissertation presents studies on high-temperature molten salts and ionic liquids. Both molten salts and ionic liquids are materials composed solely of positive and negative species and the difference between these is mainly based on the temperature at which they melt. Molten salts tend to melt at high temperature (often at several hundred degrees Celsius) whereas ionic liquids melt at or around room temperature. This dissertation seeks to understand their bulk- and interfacial behavior using computational techniques such as molecular dynamics and other theoretical analysis tools. For example the computationally derived structure function (S(q)), a quantity that can be directly contrasted with X-ray scattering measurements, can be used to validate simulation results and explain the meaning of experimental findings on an atomistic length scale. Data derived from simulations can reveal a rich amount of details about the contribution of different liquid subcomponents that are difficult or simply impossible to extract from experiments alone. In other words, we use experiments to verify the accuracy of simulations, and simulations to explain the meaning of experimental findings. This dissertation also discusses a way to partition the computationally derived Fresnel-normalized specular X-ray reflectivity (R(q)/R_F(q)), a quantity that can also be directly compared with experiments, to interpret the structure associated with ion arrangements at and away from interfaces.

Overall, we hope that results presented in this dissertation will provide useful insight from a theory and computational perspective into the structure and dynamics of these fascinating systems which have multiple current- and potentially new applications in multiple areas of chemistry and technology in general.