(2p) Connecting Computational Chemistry and Its Applications at All Scales - from Ab Initio Quantum Chemistry to Continuum Modeling

The understanding of a new chemical system is usually driven by experiments, and is supported by theory and computations which provide intuitions at the detailed level. Recent advances in computational chemistry amplify its significance in the field. In particular, the achievement in exploiting graphical processing units (GPUs) to solve the electronic Schrodinger equation pave the way for hypothesis-free, on-the-fly ab initio molecular dynamics simulations with access to larger spatial and longer time scales. However, loose connection still persists in computational chemistry at scales ranging from quantum chemical level to mesoscale material and macroscopic continuum scale. My research group will be centered on connecting computational chemistry at all scales, and addressing a wide range of its global needs from energy conversion and storage to material design, electronic devices, and biochemistry. With my expertise in quantum chemistry and its applications, kinetic rate theory, fluid dynamics modeling, and continuum mechanics, I envision my group will make a paradigm shift in the field of computation and modeling. My group will be particularly interested in achieving the following two goals. 1) Proposing efficient, accurate and robust computational methods for constructing chemical network in an assembly of molecules using ab initio molecular dynamics. 2) Developing novel mesoscale molecular modeling theory to bridge the gap between quantum chemical, atomic scale simulation with modeling of system response at continuum level. To achieve the goals, in this poster, I demonstrate four examples, each at a particular spatial (or temporal) scale, as the starting points along this research journey.

In the first example, we apply ab initio multiple spawning (AIMS) method to study how photomechanical switch work under photoexcitation. Specifically, we study the dynamics of diarylethene derivatives on their excited and ground state, and explore the impact of substitutions on their photochemical properties. This results in this work provide insights for inverse design of novel photomechanical switch materials.

The second example shows our success in combining computational reaction discovery with microkinetic modeling, taking high-temperature methane pyrolysis as the test case. Reaction network of methane pyrolysis is automatically constructed in a recently developed ab initio nanoreactor, which describes chemical reactivity in a large assembly of molecules without any preconceptions. Examples of newly integrated kinetic modeling and sensitivity analysis workflow highlights the potential of the nanoreactor approach for systematic reaction network exploration.

The third example demonstrates a case of connecting the first-principle molecular simulation with mesoscale computational modeling. Specifically, I am unraveling the mechanochemical activation mechanism of a functional polymer material embedded with radical cascading mechanophores. At atomic/molecular level modeling, I am focusing on deciphering the radical cascading mechanism the mechanophore under external mechanical forces. In the meantime, I will show the state-of-art development of a mesoscale computational modeling suite for solid-state polymers, and how it achieve on-the-fly communicates with ab initio quantum chemistry simulations.

Lastly, I present a series of work in my Ph.D. study which combines microkinetic models and continuum simulations. This work series involve theoretical development of compact reaction kinetic models for practical fuels in combustion applications. In particular, we proposed a hybrid chemistry (HyChem) method for complex liquid fuels. HyChem has been successfully integrated into computational fluid dynamics (CFD) and brings computational modeling of turbulence chemistry interaction to the next level.

Teaching Interests

My teaching philosophy centers around cultivating student thinking on three different aspects: scientific intuition, critical thinking, and a high-level perspective. I believe that a good scientist or engineer is not only equipped with a broad range of core engineering-physics principles, but also possesses a developed scientific intuition. A scientist with this skill is able to see through a mathematical equation and think about the physical ramifications and insight that the equation offers. In classrooms, I like to encourage students to “visualize” the physics behind scientific principles, instead of teaching formulas and derivations alone, and gradually develop their intuition. Critical thinking is essential to scientific breakthroughs and innovation. Most revolutionary advancements in science are not achieved by incrementally improving an existing theory, but instead by proving it wrong. In my classroom, I will encourage students to think beyond the textbook, and establish their independent and critical thinking. This can be achieved by inspiring students with critical questions on classic theories and engineering problems, and also by encouraging students to engage in discussions in and outside of class. The third element of the scientific toolbox that I believe is invaluable in young scientists is the ability for a researcher to work not only on the details, but to have a view of the bigger picture problem they are trying to solve. My students should believe that they are poised to tackle the hardest and most impactful problems that the world has to offer. To ensure this empowerment, I will inclusively introduce global news and technology challenges in discussion with students and in lectures, and stimulate students with thinking broader than an individual homework assignment or project.

The teaching philosophy of mine evolves as teaching experience accumulates throughout my academic career. From my past experience as a Teaching Assistant for a graduate-level course, Combustion Fundamentals at Stanford, my passion for teaching elevated a lot. I was responsible for creating the material for and teaching problem sessions, and also holding office hours. I also had the opportunity to teach three lectures when the instructor was away and to offer a guest lecture for the same course in the next year. In the lectures I taught I tried to encourage students to consider the physics intuition behind the species transport phenomena in flames. During problem sessions and office hours, I encouraged students to raise critical questions not only on problem sets, but also on other aspects of the course such as the validity and limitations of well-known theories. Students enjoyed this process and sometimes surprised me with exceptional questions. My passion to engage and inspire students are not limited to the classroom. Throughout my studies as a graduate student and a postdoc at Stanford, I have mentored a few graduate students working on different research projects. From these experiences, I learned that it is necessary to apply specific mentoring approaches to each individual with different personalities. Over the course of interacting with the students, I found that they not only generated very useful results, but also developed physical insights under my guidance. More interestingly, I have always been inspired after discussing with the students, since they were able to raise questions with creativity. Overall, I found these mentorship experiences are extremely rewarding.