(4cc) Computation and Theory of Materials with New Quantum Properties

Engineering new materials for energy storage, information sciences, and sustainable chemistry requires not only a fundamental understanding involving the quantum mechanical phenomena by which they operate at the atomic-level, but also robust design principles that can be implemented at the macroscale. My research has focused on elucidating the mechanisms for a wide range of processes in materials chemistry using computational simulations and modeling. My group will address challenges in uncovering how chemical reactivity and structural changes at the microscopic level impact the overall electronic properties of materials by developing and applying computational techniques at the intersection of quantum and statistical mechanics. The overall goal will be to understand and design materials that exhibit novel quantum properties.

In my postdoctoral work, I investigated the formation of spin defects (e.g., ­­defects with isolated electron spins) in silicon carbide that can serve as qubits with long decoherence times and are ideally suited to host quantum technology platforms, using molecular dynamics, enhanced sampling, and density functional theory. This work uncovered a general method for investigating and discovering new spin defects whose control would be applicable in quantum computing and sensing, and I delineated the mechanisms by which defects form at high temperatures, which are consistent with optical measurements during thermal annealing [1]. In addition, I developed novel sampling methods for computational simulations using artificial neural networks to map the free energies for the dissociation of molecular nitrogen on ruthenium for the synthesis of ammonia to gain insights into the role of vibrational modes of the metal catalyst on molecular gas decomposition [2]. Furthermore, I probed the molecular mechanisms for the reversible covalent bond formation in polymers synthesized in catalyst-free conditions from first-principles simulations, to design sustainable reactions that eliminate the use of hazardous chemicals in chemical synthesis routes [3]. My ongoing work is studying lithium-ion transport in polymer-inorganic ceramic composites using machine learning techniques and atomistic simulations to elucidate how interfaces created between soft and hard materials impact the diffusion of ions in lithium-ion batteries.

My Ph.D. work focused on developing new computational techniques that can simulate energy transport processes at the nanoscale in materials such as quantum dots and conjugated polymers, for designing next-generation photovoltaics and LEDs. I constructed a theoretical framework, based on analytical theories and numerical simulations, for measuring diffusion lengths of excitons—bound electron-hole pairs—in quantum dot solids from photoluminescence quenching experiments [4]. My model has since then been used by other researchers for also measuring charge carrier diffusion lengths in other systems such as organic photovoltaics and metal-halide perovskites. I also developed models that explained how organic ligands affect the vibrational frequencies of colloidal nanocrystals owing to the mass-loading effect based on the continuum linear elasticity theory [5,6,7]. Moreover, I developed kinetic Monte Carlo models of exciton diffusion in disordered quantum dots, and demonstrated how the presence of energetic disorder leads to subdiffusive transport [8, 9, 10]. I also extended my previous exciton diffusion models to study charge carrier dynamics in quantum dot solids [11,12], and predicted that charge carrier mobility can increase with decreasing temperature due to temperature-dependent structural changes, which was later measured by synchrotron small-angle X-ray scattering technique [13]. Finally, I developed a new constrained adiabatic dynamics model, to simulate exciton migration in coarse-grained conjugated polymers [14] to understand how the structure of the polymer network impact exciton diffusion length in organic photovoltaics.

Teaching Interests:

My primary aim in teaching is to instill curiosity in students, so they ask questions about how and why physical phenomena occurs and behaves in particular ways, and inspire them with creativity in discovering explanations or solutions. To achieve such goals, I will equip students with the knowledge and ability to test new ideas. As an undergraduate majoring in Chemical Engineering and Chemistry at Johns Hopkins University, I taught core chemical engineering and chemistry courses, including Chemical Separations Processes and Organic Chemistry I and II, to undergraduates at the Learning Den in Hopkins. Additionally, at Hopkins, I gained first-hand experience teaching fundamental concepts in thermodynamics along with computational techniques while serving as a teaching assistant for a chemical engineering elective course (Computational Protein Structure Prediction). Since then, I have been strongly engaged in teaching computational modeling/simulation methods to students at several levels, including introducing fundamental concepts at the undergraduate level or investigating more advanced topics in graduate courses. At the Massachusetts Institute of Technology (MIT), I taught first-year graduates on numerical methods as applied to chemical engineering and led recitations lectures for the course every week. I also taught a graduate-level course in Statistical Mechanics at the chemistry department, where I introduced programming exercises for students to learn and explore phase transitions using Ising models.

Based on my formal education, teaching experience, and research areas, I am confident in my ability to teach any undergraduate and graduate core-level chemical engineering courses, particularly statistical mechanics, physical chemistry applied to chemical engineering, heat and mass transfer, and reaction engineering/kinetics. I am also interested in courses that combine chemical engineering, theoretical chemistry, materials physics, and numerical methods, such as “Molecular engineering for energy storage, transfer, and processing.”

Selected Awards:

DOE ASCR Leadership Computing Challenge, 2021

1^st Place, Best Presentation, Oral, Graphics, DOE Center for Excitonics, Harvard-MIT, 2018

1^st Place, AIChE Area 8E Graduate Student Award, AIChE Meeting in Minneapolis, MN, 2017

Energy Fellowship, MIT, 2012

NSF Graduate Research Fellowship, 2012

Chemistry Student Award, ACS Maryland Chapter, 2012

NSF Undergraduate Research Fellowship, Harvard SEAS, 2011

AIChE Award for Scholastic Achievement, Johns Hopkins University, 2011

Provost’s Undergraduate Research Award, Johns Hopkins University, 2010

Selected Publications:

1. E. M.Y. Lee, A. Yu, J. J. de Pablo, and Giulia Galli, “Stability and Molecular Pathways to the Formation of Spin Defects in Silicon Carbide” Under review, 2021
2. E. M.Y. Lee, T. Ludwig, B. Yu, A. Singh, F. Gygi, J. K. Norskov, and J. J. de Pablo, “Network Sampling of the Free Energy Landscape for Nitrogen Dissociation on Ruthenium,” Journal of Physical Chemistry Letters, 12, 2954-2962, 2021
3. E. M.Y. Lee, N. Dolinsky, K. Michael Salerno, J. Dennis, S. Rowan, and J. J. de Pablo, In preparation, 2021
4. E. M.Y. Lee and W. A. Tisdale, “Determination of exciton diffusion length by transient photoluminescence quenching and its application to quantum dot films,” Journal of Physical Chemistry C, 119(17), 9005-9015, 2015
5. E. M.Y. Lee, A. J. Mork, A. P. Willard, and W. A. Tisdale, “Including surface ligand effects in continuum elastic models of nanocrystal vibrations," Journal of Chemical Physics, 147, 044711, 2017
6. A. J. Mork, E. M.Y. Lee, N. S. Dahod, A. P. Willard, and W. A. Tisdale, “Modulation of low- frequency acoustic vibrations in semiconductor nanocrystals through choice of surface ligand,” Journal of Physical Chemistry Letters, 7, 4213-4216, 2016
7. A. J. Mork, E. M.Y. Lee, and W. A. Tisdale, “Temperature dependence of acoustic vibrations of CdSe and CdSe-CdS core-shell nanocrystals measured by low-frequency Raman spectroscopy,” Physical Chemistry Chemistry Physics, 18, 28797-28801, 2016
8. E. M.Y. Lee, W. A. Tisdale, and A. P. Willard, “Can disorder enhance incoherent exciton diffusion?" Journal of Physical Chemistry B, 119, 9501-9509, 2015
9. M. Akselrod, F. Prins, L. V. Poulikakos, E. M.Y. Lee, M. C. Weidman, A. J. Mork, A. P. Willard, V. Bulovic, and and W. A. Tisdale, “Subdiffusive exciton transport in quantum dot solids," Nano Letter, 14(6), 3556-3562, 2014
10. E. M.Y. Lee, W. A. Tisdale, and A. P. Willard. “Perspective: Nonequilibrium dynamics of localized and delocalized excitons in colloidal quantum dot solids.” Journal of Vacuum Science & Technology A, 36, 068501, 2018
11. R. H. Gilmore, E. M.Y. Lee, M. C. Weidman, A. P. Willard, and W. A. Tisdale, “Charge carrier hopping dynamics in homogeneously broadended PbS quantum dot solids,” Nano Letters, 17, 893-901, 2017
12. R. H. Gilmore, Y. Liu, N. S. Dahod, W. Shcherbakov-Wu, E. M.Y. Lee, M. C. Weidman, H. Li, J. C. Grossman, and W. A. Tisdale. “Epitaxial dimers and auger-assisted de-trapping in PbS quantum dot solids” Matter, 1, 250, 2019
13. R. H. Gilmore, S. W. Winslow, E. M.Y. Lee, M. N. Ashner, K. G. Yager, A. P. Willard, and W. A. Tisdale. “Inverse temperature dependence of charge carrier hopping in monodisperse quantum dot solids.” ACS Nano, 12, 7741, 2018
14. E. M.Y. Lee and A. P. Willard. “Solving the trivial crossing problem while preserving the nodal symmetry of the wavefunction” Journal of Chemical Theory and Computation, 15, 4332,
15. E. M.Y. Lee, X. Zhu, and D. R. Yarkony “On the electronic structure of the low lying electronic states of vanadium trioxide,” Journal of Chemical Physics, 139, 044303, 2013.