(7q) New Generation of Polarizable Reactive Force Fields for Multiscale Simulations of Complex Materials

Critical to the development and manufacturing of new generations of functional materials is the design of the non-equilibrium dynamical processing to achieve desired microstructures and transport properties. Here, we need methods for in silico designing and simulating of such processes to produce novel functional materials and to facilitate technological breakthroughs. These methods must be able to describe: I) non-equilibrium transport phenomena (e.g. of charges, ions, atoms, mass, and defects) in bulk and across interfaces over multiple length and time scales, II) the dynamics of phase changes during material growth, processing and operation, and III) the microstructures of complex heterogeneous structures that provide the desired functional properties.

Non-equilibrium phenomena determine the behavior of materials for practical applications, and understanding them is critical to optimize material synthesizability, characterization, and design trade-offs. Specific examples of non-equilibrium in material systems include ionic and electronic conductance in semiconductors, synthesis of thin films and nanostructures (e.g. crystallization), and functional self-organizing soft materials (e.g. adsorption polymers, catalyst support materials, soft magnets), condensed phase reaction kinetics. In all these materials, non-equilibrium dynamics determines all structural characteristics and their properties.

We need methods that provide the accuracy of Quantum Mechanics (QM) for reactive non-equilibrium dynamics simulations of extremely large spatial scales (1 billion atoms to describe a system of 100 nm on a side) and time scales (milliseconds to seconds) to characterize the non-equilibrium dynamical processes required to synthesize complex chemical and material systems. At this level we need to match to the continuum simulations required for developing manufacturing processes.

Successful Proposals: Department of Energy, National Science Foundation, Office of Naval Research

Postdoctoral Projects:

1. â??New Generation Reactive Force Fields based on Valence Bond Concepts with Polarized Charge Distributions (VaPoX), Fundamental Concepts and Applicationsâ?

2. â??Quantum Optimized Polarizable Charge Equilibration (PQEq) For Predicting Accurate Charges in Molecules and Solids

3. â??Prediction of Structures and Properties of Green Energetic Materials from Density Functional Theory (DFT) and Reactive Molecular Dynamicsâ?

Advisor: Prof. William A. Goddard III, Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech)

PhD Dissertation: 

â??A process-based molecular model of silicon carbide (SiC) nano-porous membranesâ?

Advisors: Profs. Muhammad Sahimi and Theodore T. Tsotsis, Mork Family Department of Chemical Engineering and Materials Science, University of Southern California (USC)

Research Experience:

My research focuses on first principles-based multiparadigm, multiscale strategies for simulating complex materials processes. It contains, 1) development of advanced computational algorithms for atomistic modeling, and 2) their applications to current problems in chemistry and chemical engineering. For example, I have developed VaPoX, a new generation of polarizable reactive force field. VaPoX allows an accurate description of the local polarization of atoms needed to describe dynamic dielectric properties. In addition, it uses valance bond concept to accurately describe the bonding. VaPoX is a great deal of progress toward in silico design and simulation of non-equilibrium dynamical processes required to manufacture complex functional materials to achieve novel functional and transport properties.

These research projects bring together concepts in physics, chemistry, chemical engineering, numerical methods and algorithms analysis that I have developed during my doctoral and post-doctoral work studying chemical phenomena. I have received several awards for excellence in my research including the University PhD Achievement Award (USC 2013), the Material Engineering and Science (MESD) Award (AIChE 2012), the Soft Matter Journal Award (AIChE 2012), the Mork Family Department of Chemical Engineering & Materials Science Best PhD Thesis Award (USC 2013), and Project Navigator Ltd. Environmental Engineering Awards (USC 2011 and 2012).

Future Plans: 

There is an economic and environmental imperative to develop new and alternative energy technologies. As a professor, I would like to continue developing polarizable reactive force fields to design new functional materials and to facilitate technological breakthroughs.

I propose to build a new formulation of polarizable reactive force fields based on my previous successes (e.g. VaPoX) but with the goal of matching the highest level QM while making it more systematic so that the transferable reactive force fields will be attainable. This will enable not only my group but also a broad range of scientists to study nonequilibrium, adiabatic and non-adiabatic, reactive dynamics simulations of large-scale functional material systems. I would like to prove that it is possible to construct a generic force field capable of describing complex reaction dynamics at nearly the accuracy of QM on systems that are many orders of magnitude larger than QM size and time-scales.

My research direction is motivated by a diverse set of applications including energy technologies, nanotechnology, biomaterials, catalysts, and organic materials where experimental approaches are inaccessible and/or inefficient. In particular, I would like to develop new polarizable reactive force fields to design and study high energy density materials under extreme conditions, nonporous membranes for gas separation, energy storage and conversion, hydrogen storage and supercapacitors, gas purification, fuel cells, solar cells, and Liâ??ion batteries.

As a faculty, I hope to educate new engineers and establish an externally funded and internationally renowned research group that develops energy technologies. My research group will focus on socially important problems and the translation of scientific studies into practical technologies. I will foster a learning environment and will actively maintain collaborations with colleagues from within the engineering community and from diverse fields. Scientific advancement is best accomplished through efficient communication of results and analyses; as such, I will strive to disseminate my works at the highest scientific levels as well as to the broader public. I am confident in my abilities to manage a research group and I am highly motivated to begin working on the development of new functional materials and energy technology.

Teaching Interests:

I have experience teaching and mentoring students in the classroom and in the laboratory. As a teaching assistant I have given lectures and tutorial sessions in Transport Phenomena (i.e. Mass Transfer, Heat Transfer, and Viscous Flow), Reactor Design and Kinetics, and Advanced Engineering Mathematics. My teaching efforts and strategies received commendable reviews and ratings at USC. I received university outstanding teaching assistant award in the category of chemical engineering (2012) and Mork Family Department of Chemical Engineering and Materials Science best teaching assistant award (2013). In addition, I have received several offers from prestigious institutions such as Harvey Mudd College to teach undergraduate chemical engineering courses. I am enthusiastic about the opportunity to teach undergraduate and graduate courses including Quantum Mechanics, Computer Simulation and Modeling, Transport Phenomena, Chemical Reaction Engineering, Engineering Thermodynamics, and Advanced Engineering Mathematics.