Modeling Excited Molecules and Materials
Primary Research Area
Theoretical and Computational (Th)
Other Area(s) of Interest
Chemical Physics (CP)
(Research Description PDF)
The Levine group works to develop and apply theoretical tools and computational methods to model the dynamics of electronically excited molecules and materials. In particular, we work with ab initio nonadiabatic molecular dynamics methods, which model the coupled electron-nuclear dynamics that determine photochemical and photophysical outcomes.
A primary focus of the Levine group is modeling advanced materials with applications in solar energy conversion, light emission, chemical sensing, photocatalysis, and other fields. In doing so, we have developed theoretical tools and advanced software that enable us to apply ideas from molecular chemistry to complex materials. We have demonstrated that, like molecules, semiconductor nanomaterials may non-radiatively decay to the electron ground state via conical intersections, molecular structures at which different electronic states become degenerate and are strongly coupled. Many students in the Levine group develop and apply methods to more accurately and efficiently model these intersections, thus enabling us to understand semiconductor photophysics more deeply and rigorously than previously possible.
Another primary focus of work in the Levine group is modeling nonadiabatic molecular dynamics in dense manifolds of electronic states. Many interesting chemical problems involve dynamics on many electronic states, from hundreds up to an infinite continuum. Such problems include chemical reactions involving free electrons, semiconductor and plasmonic materials, molecules in strong laser fields, and molecules and materials exposed to radiation. The Levine group develops and applies methods to accurately model these dynamics, coupling time-dependent electronic structure theory to novel nonadiabatic molecular dynamics schemes capable of accurately navigating these dense manifolds of states.
A third focus of the Levine group is the fundamental theory of dynamics near conical intersections. Two important matrix elements, known collectively as the nonadiabatic couplings, diverge toward infinity at conical intersections. Their large magnitude results in efficient transfer of population between electronic states, but such singularities are a significant challenge to those modeling dynamics near intersections. The Levine group has developed strategies for addressing these singularities that enable more accurate and efficient modeling of dynamics near conical intersections.
Much of our work is enabled by advanced computer hardware. Some students in the Levine group work to develop software that utilizes graphics processing units (advanced computer processors designed for graphical applications such as computer games) to solve the Schrödinger equation. This strategy enables us to model larger systems with more electronic states over longer timescales with greater accuracy than is possible with more traditional hardware.
Dynamics of Recombination via Conical Intersection in a Semiconductor Nanocrystal, W.-T. Peng, B. S. Fales, Y. Shu, and B. G. Levine, Chem. Sci. 2018, 9, 681.
Understanding Nonra d i a t i ve Recombination through Defect-Induced Conical Intersections, Y. Shu, B. S. Fales, W.-T. Peng, and B. G. Levine, J. Phys. Chem. Lett. 2017, 8, 4091.
The Best of Both Reps: Diabatized Gaussians on Adiabatic Surfaces, G. A. Meek and B. G. Levine, J. Chem. Phys. 2016, 145, 184103.
Nanoscale multireference quantum chemistry: Full configuration interaction on graphical processing units, B. S. Fales and B. G. Levine, J. Chem. Theory Comput. 2015, 11, 4708.
Defect-induced conical intersections promote nonradiative recombination, Y. Shu, B. S. Fales, and B. G. Levine, Nano Lett. 2015, 15, 6247.
Evaluation of the time-derivative coupling for accurate electronic state transition probabilities from numerical simulations, G. A. Meek and B. G. Levine, J. Phys. Chem. Lett. 2014, 5, 2351.
B.S. Chemical Engineering 2001, Univ. of lllinois at Urbana-Champaign
Ph.D., Chemistry, 2007, Univ. of lllinois at Urbana-Champaign
Post-Doctoral Researcher, 2007-2011, Univ. of Pennsylvania and Temple University