46451-AC6
Calculations of Interfacial Free Energies Between Water and Ice from Molecular Simulations
When we began to work on the proposed work on the simulation of water interfacial free energies a couple of months after the proposal is funded by PRF, we discovered that an almost exact simulation was done and published in Physical Review Letters (100, 036104 (2008)) using the methodology developed in our group. This discovery led us to begin to work on the second part of the proposed research, namely, the calculation of interfacial free energies between sodium chloride aqueous system and the ice. In order to achieve that goal the first step is to develop an efficient method to estimate the coexistence conditions between an electrolyte solution and ice.
To this end, we developed a thermodynamic perturbation methodology to calculation free energies and correlation functions of liquid and solid hard-sphere mixtures using the fundamental measure density functional theory. An application to Lennard-Jones mixtures led to the resulting azeotrope and spindle-type solid-liquid phase diagrams which are in good agreements with the corresponding ones from computer simulations (publication 1). We also applied our theoretical methodology to the calculation of the phase diagram of Cu-Au alloy .To improve the accuracy of the computed phase diagram we developed a systematic approach to optimize the model potential of Au-Cu by adjusting the melting temperature of the pure Au to its experimental one. With such an optimized potential the computed Au-Cu alloy phase diagram is in good agreements with the experimental one for the whole composition range (publication 2).
Now we are in the process to apply the above theory 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 set up our simulation system to calculate 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.
