(6fg) First Principles-based Multiparadigm, Multiscale Strategies for Simulating Complex Materials Processes

Authors: 
Naserifar, S., California Institute of Technology

My research focuses on, (1) development of advanced computational algorithms for atomistic modeling, and (2) their applications to current problems in chemistry and chemical engineering. The research lies at the interface of physics, chemistry, chemical engineering, and numerical and algorithms analysis. The aim of my research is to study processes that are of current interest from both small- and large-scale perspectives. The research is motivated by diverse applications including energy technologies, nanotechnology, biomaterials, catalysts, and organic materials where experimental approaches are inaccessible and/or insufficient. In principle, any material is a collection of particles including nuclei, electrons, and phonons. To engineer alternative materials for improved or new functionalities, it is crucial to understand chemistry and energetics of the materials, which govern their mechanical, electronic and thermal properties. I use ab-initio quantum mechanics (QM) and density functional theories (DFT) to achieve the goals of my research. Such methods fail, however, when more realistic systems must be studied. For instance, micro-second studies of systems involving large number of particles and high temperature are far beyond the scope of QM and DFT methods. Much of my research is focused on bridging first-principle simulations, normally feasible for small systems, and large-scale simulations necessary for studying systems of practical interest. I have extensive experience in development of reactive force fields, such as ReaxFF as well as invoking reactive force fields to study real-life problems.

I will present an example of such problems by discussing a process-based molecular model of nano-porous silicon carbide (SiC) membrane. A broad class of important materials, such as carbon molecular sieves, SiC, and silicon nitride, are fabricated by temperature-controlled pyrolysis of preceramic polymers. In particular, the fabrication of SiC membranes by pyrolysis of a polymer precursor that contains Si is quite attractive for separation of hydrogen from other gases. It has been quite difficult to extract atomistic-scale information about such SiC membranes since they are amorphous. I will discuss development of a reactive force filed and its application for the thermal decomposition of hydridopolycarbosilane (HPCS) to form SiC nanoporous membranes. I will also highlight my future research plans which I believe are of substantial scientific merit and national interest which fit well with a range of research programs launched by different funding agencies.