Miscibility of ionic and neutral fluids in low dimensional systems: A computational investigation of room temperature ionic liquids / hydrocarbon mixtures
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- Institutt for fysikk 
A new class of organic ionic compounds, liquid at ambient conditions and collectively known as room temperature ionic liquids (RTIL) could represent the solvents of choice to extract hydrocarbons from pores and cracks in rocks. Modelling and predicting the phase diagram of these systems at an acceptable cost is therefore a valuable target for computational investigations. To this aim, a suite of computer codes have been developed and tested to determine the equilibrium structure and thermodynamic properties of ternary fluid mixtures consisting of cations and anions dispersed at low concentration into a neutral molecular solvent. The suite includes molecular dynamics (MD) and Monte Carlo (MC) simulation programs in the canonical, grand canonical and Gibbs' ensemble formulation, as well as state of the art programs able to solve integral equations for the correlation functions of liquids whose constituent particles interact with each other through pair potentials. The preliminary studies whose results are reported in the thesis display a wide variety of phases and phase transitions, from the usual liquid-vapour and crystallisation transitions, to more exotic liquid-liquid separations, meso-phase formation, and ionic to dipolar transitions. This rich picture reflects the interplay of short- and long-range forces in the Hamiltonian of the fluid system. The investigation has been extended to analyse by MC simulation the effect of dimensionality on the phase diagram of these ternary fluid mixtures. The sizeable implementation effort documented in the thesis will provide in the near future the basis for an extensive analysis of equilibrium properties, and phase diagrams in particular, of RTIL-hydrocarbon mixtures, using simplified and coarse grained but still realistic models.