2018-06-13
10:15 at HCP F 43.4

Thermodynamic analysis of Lennard-Jones binary mixtures using Kirkwood-Buff theory

Katerina Galata

National Technical University of Athens, Greece

The ability to extract thermodynamic properties of mixtures from molecular geometry and interactions is one of major advantages of atomistic simulations, but, at the same time, can be a great challenge, especially for statistical properties such as Gibbs energy of mixing (Δ_mixG). This challenge becomes even greater in the case of mixtures of complicated molecules or macromolecules. Kirkwood-Buff theory offers a promising avenue for estimating Δ_mixG from atomistic simulation of binary mixtures. Molecular dynamics simulations are performed of both ideal and real binary Lennard- Jones mixtures at various mole fractions to produce the systems that are studied. The estimation of Kirkwood-Buff integrals will take place by two different methods and the most efficient one will be identified. Then the methodology used will be validated by comparing several thermodynamic properties of the ideal mixtures against the theoretical expressions of thermodynamics. Finally, the calculation of the mixing thermodynamic properties for the real mixtures, namely the enthalpy, Gibbs energy, and entropy of mixing, as well as their excess parts relative to an ideal solution, will be explicitly presented. These results will be compared against the predictions of the well-known modifies Benedict-Webb-Rubin equation of state for Lennard-Jones systems.