(6jp) Designing Chemical Reactivity at the Nanoscale using Molecular Simulation

There is great need for methods that can simulate both reactivity and condensed phases at the molecular level. Quantum mechanical (QM) methods can model the changing electronic environment as a reaction occurs, but are generally too small— O(100) atoms—to represent the condensed phase. Classical molecular mechanics (MM) simulations can be much larger, but cannot model reactivity. I am interested in employing and developing methods that can address both aspects—including QM/MM simulations, reaction ensemble Monte Carlo, and quantum-accurate reactive classical force fields.

Some specific research problems include developing methods to assess ionization in strong electrolytes (e.g. protic ionic liquid formation); modeling nucleation under reactive conditions (e.g. corrosion of plutonium); adding functionality to solid supports for reactive absorption (e.g. in amine-functionalized metal-organic frameworks); and developing quantum-accurate reactive force fields compatible with classical solvents (e.g. SPC water).

Teaching Experience:

I am energized by teaching and interacting with students at all levels. As a teaching assistant, I volunteered to give lectures while professors were away on travel. My goal was to help students understand the foundational assumptions of each equation we derived. They recognized my hard work by voting me TA of the Year.

As a grad student and in both my postdocs, I’ve sought out opportunities to lead elementary, middle, and high school students in hands-on STEM demos that connect molecular-level visualization to classroom experiences. For example, I’ve developed videos of molecular dynamics (MD) to pair with the following demos:
(*) Demo: crush a metal can by pulling a vacuum inside
MD video: a box of air that shows how the molecules move and collide

(*) Demo: pour super-cooled water and watch it freeze instantaneously
MD pictures: nucleation of an ice crystal in super-cooled water

(*) Demo: pour liquid nitrogen on the floor
MD Video: a nano-sized droplet of liquid nitrogen boils after contacting a hot surface

Teaching Interests:

I will teach anything. I would be particularly interested in teaching chemical reaction engineering, thermodynamics, and mass transfer, but would be happy to teach introductory classes, too. I am eager to develop elective courses on molecular simulation at both the undergraduate and graduate levels, and graduate courses in statistical mechanics, reaction rate theory, and mass transfer.

Research Experience:

My research career has been focused on modelling rare events and chemical reactions. As a grad student, I developed transition path sampling methods for modeling dynamics of rare events. My methods were used in a collaboration, published in Nature, to study ice nucleation. In my first postdoc, I developed general Monte Carlo methods for modeling reaction equilibria and investigated CO2 absorption in ionic liquids. In my second postdoc, I am modeling the corrosion of plutonium.

Selected Publications:

L Lupi, A Hudait, B Peters, M Grunwald, RG Mullen, A Nguyen, V Molinero, “Role of Stacking Disorder in Ice Nucleation” Nature 551.7679 218-222 (2017)

http://dx.doi.org/10.1038/nature24279

ZA Levine, MV Rapp, W Wei, RG Mullen, C Wu, GH Zerze, J Mittal, JH Waite, JN Israelachvili and J-E Shea, “Surface force measurements and simulations of mussel-derived peptide adhesives on wet organic surfaces” Proceedings of the National Academy of Sciences 113.16 4332-4337 (2016) http://dx.doi.org/10.1073/pnas.1603065113

RG Mullen, EJ Maginn, “Reaction ensemble Monte Carlo simulation of xylene isomerization in bulk phases and under confinement” Journal of Chemical Theory and Computation 13.9 4054-4062 (2017) http://dx.doi.org/10.1021/acs.jctc.7b00498

JK Shah, E Marin-Rimoldi, RG Mullen, …, EJ Maginn, "Cassandra: An open source Monte Carlo package for molecular simulation." Journal of Computational Chemistry 38.19 1727-1739 (2017) http://dx.doi.org/10.1002/jcc.24807

RG Mullen, J-E Shea and B Peters, "Transmission coefficients, committors, and solvent coordinates in ion-pair dissociation" Journal of Chemical Theory and Computation 10.2 659-667 (2014) http://dx.doi.org/10.1021/ct4009798