Reports: AC6
46451-AC6 Calculations of Interfacial Free Energies Between Water and Ice from Molecular Simulations
During the past year, we have made two major progresses with the support of this PRF grant.
Motivated by our recent proposition on the possibility of using dielectric continuum models to interpret experimental measurements of solvation dynamics in room temperature ionic liquids (Journal of Physical Chemistry A, 110, 8623(2006)), some detailed simulation studies are performed to test the validity of our proposition. From these simulation studies it seems to be justified that an extended Debye-Hückel continuum model can be used to understand the solvation dynamics of ionic fluids. The theoretical underpinning of such an extended Debye-Hückel model is presented from the general dispersion relation in electrodynamics. The connection with the static extension from the dressed ion theory of electrolyte solutions is also discussed. Such a connection between the Debye-Hückel theory and the dispersion relation may be exploited to enhance our understanding of the electric double layer problem not only for the static case, but also for dynamic situations. The result is published in the Journal of Chemical Physics, 130, 044503(2009). The above result is significant because it provides a possible route to develop a perturbation theory approach to ionic fluids.
For the first time, a perturbation theory is developed to calculate a solid-liquid interfacial free energy, including its anisotropy for systems with short-range interactions potentials based upon a hard sphere reference system. The method is applied to the systems with inverse-power and Lennard-Jones pair potentials as well as to metallic system with embedded-atom model potential. The results are in reasonable agreement with the corresponding ones obtained by the molecular dynamics simulations. A manuscript based upon this work is in preparation.
A combination of the above approach will pave the way to estimate the coexistence conditions of the sodium chloride aqueous solutions. Such a strategy is essential as brute force simulations to locate the coexistence conditions for molecular mixture systems are extremely time consuming. Once we have the coexistence conditions we should be able to compute the interfacial free energies. These results can be used to make direct correlations with the experimental measurements from Koon and coworkers as proposed in our proposal.
