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

CBET-0756641

Siepmann

Accurate knowledge of the phase equilibria and other thermophysical properties of complex chemical systems is of enormous fundamental and practical importance. The success of molecular simulation in predicting thermophysical properties and 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.

Intellectual Merit:

Force Field Development. The main goal of this project is to advance the development of the TraPPE (transferable potentials for phase equilibria) force field (FF) which consists of three levels. The first-level (TraPPE UA) is designed for simplicity and computational efficiency with good accuracy and makes use of united-atom representations for alkyl segments. The second level (TraPPE EH) is aimed at improved accuracy for mixtures of non-polar or weakly polar compounds and explicitly includes alkyl group hydrogens and some lone-pair electron and bond-center sites. The third level (TraPPE pol) is directed solely at the highest possible level of accuracy and transferability and here both the van der Waals and electrostatic interactions can respond to changes in the environment. It is proposed to extend (i) the TraPPE UA FF toward the building blocks of common polymers, (ii) the TraPPE EH FF toward rings found in pharmaceutical molecules, and (iii) the TraPPE pol FF to water, alkanes, alcohols, and ethers. Algorithm Development. This project also addresses novel Monte Carlo approaches for first principles simulations of phase equilibria and biased Monte Carlo methods to improve the sampling of phase transfers and spatial distributions in microheterogeneous fluids and crystalline solids. Applications. Molecular simulations using the transferable force fields will be employed as an engineering tool to predict thermophysical properties of a variety of complex systems, thereby adding to the available experimental database. The simulations will also provide a wealth of microscopic level insight into how molecular architecture and composition determine macroscopic phenomena. In particular, simulations will be carried out to investigate (i) solvation in microheterogeneous fluids, (ii) interfacial and surface properties of aqueous mixtures containing non-ionic surfactants and of common oligomers, and (iii) polymorphism and hydrate formation for pharmaceutical solids.

Broader Impacts.

Integration of Research and Education.. The PI strives to infuse his teaching of a freshman seminar on the material world and a graduate course on thermodynamics and statistical mechanics with the excitement of discovery by integrating hands-on computational exercises and topical results from molecular simulation research. The PI has participated as science expert/co-presenter for liquids and water in ScienceWorks!, an NSF-sponsored project that seeks to improve the Minneapolis Public Schools K8 science program, and taught hands-on science classes for third graders. Development of Human Resources. Driven by the university industry partnership, which allows for extensive interactions with Drs. Ross and Schultz of 3M Central Research, St. Paul, MN, the graduate student education can be advanced in a unique and successful way. In addition, this research project will foster the participation of undergraduate students and special efforts will be made to recruit these students from traditionally underrepresented groups. Science and Engineering Infrastructure. The cyberinfrastructure will be advanced by the development of the TraPPE force field made available via a web interface and of the molecular simulation packages MCCCS (Monte Carlo for Complex Chemical Systems) and Car-Parrinello 2000, which are freely distributed via GNU General Public Licenses.