GOALI: Development of Transferable Force Fields for Phase Equilibria and Simulation Studies of Microheterogeneous Fluids

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Abstract CTS-0138393 Siepmann, Joern I. University of Minnesota - Twin Cities Accurate knowledge of the phase equilibria and other thermophysical properties of complex fluid mixtures are of enormous fundamental and practical importance. The success of molecular simulation in predicting thermophysical properties an in advancing our understanding of the relationship between molecular architecture and macroscopic observable depends on the availability of efficient simulation algorithms and accurate force fields. The goals of the research are to continue the development of three levels of transferable force fields and of biased Monte Carlo methods. The first-level force field, called TraPPE-UA (transferable potentials for phase equilibria-united atom), employs the united-atom representation for alkyl segments and simple Lennar -Jones an Coulombic terms. In the second level, called TraPPE -EH (explicit hydrogen), all atoms including alkyl group hydrogens and some lone-pair electron and bond-center sites are treated explicitly. In the third-level, called TraPPE-pol (polarizable), 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 at improved accuracy for mixtures of non-polar or apolar non-hydrogen-bonding compounds. The third level is directed solely at the highest possible level of accuracy and transferability. These transferable force fields will encompass linear, branched, and cyclic alkanes, alkenes, alkynes, alkylbenzenes, alcohols, ethers, ketones, aldehydes, esters, carboxylic acids amines, amides, nitriles, thiols, sulfides, heterocycles, perfluorinated alkanes, 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 solid-fluid equilibria, spatially heterogeneous mixtures, and hydrogen-bonded networks. 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 available experimental database. The simulations will also 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. In particular, simulations will be carried out to investigate the association of alcohols in non-polar solvents, the influence of entrainers on structure and solubility in supercritical fluids, the effect of pressurization on gas-expanded liquids, the solute partitioning between water and octan-1-ol at elevated temperatures and pressures, the structures of minimum and maximum boiling azeotropic mixtures, the liquid-liquid equilibria of alcohol/water mixtures, the partial solubilities of drugs and their sodium derivatives, and the influence of solvents on the stability of polymorphs and on solvate formation. This project will profit from extensive collaboration of a close university-industry team consisting of the PI and Dr. Sami Karaborni of Merck Research Laboratories.