The goal of the proposed research is to design two levels of transferable force fields for a large spectrum of organic molecules and water. The first level, called TraPPE (Transferable Potentials for Phase Equilibria),employs the united-atom representation and simple Lennard-Jones and Coulombic terms. In the second level, called TraPPE-pol (polarizable), all atoms are modeled explicitly, and both the van der Waals and electrostatic interactions can respond to changes in the environment. Whereas the first level is, designed for simplicity and computational efficiency with good accuracy, the second level is aimed solely at the highest possible accuracy and transferability. These force fields will allow us to study single and multi-component phase equilibria, excess properties of mixing, and to predict partition coefficients and separation factors. The transferable force fields will encompass linear, branched, and cyclic alkanes, alkenes, alkynes, alcohols, ethers, ketones, carboxylic acids, alkylbenzenes, and last, but not least, water.
In addition to the force field development, this proposal also addresses novel simulation algorithms which are targeted at efficient simulations of mixtures containing very polar and/or hydrogen-bonding species, and which will allow efficient Monte Carlo sampling for polarizable force fields. Molecular simulations using the transferable force fields will be employed as engineering tool to predict thermophysical properties of a variety of systems, thereby adding to the experimental database. The simulations will provide a wealth of microscopic-level information for complex chemical systems, thereby giving new physical insight into how molecular architecture and composition determine macroscopic phenomena.
This interdisciplinary project will profit from extensive collaboration of people with different knowledge, expertise, and perspective. On the one side, a tight university-industry team consisting of the PI and Drs. George Parks and William Parrish of Phillips Petroleum will advance the project. On the other side, Dr. Stanley Sandler, Univ. of Delaware, will provide additional guidance from the viewpoint of an experienced experimental properties worker.
