Developing an efficient and accurate quantum dynamics methods for quantum systems in complex molecular environments is one of the few remaining challenges in computational chemistry. Quantum dynamics and the resulting kinetics can involve fundamentally different mechanisms due to the delocalization and tunneling of quantum particles and can also result in transport or kinetic values surprisingly different from those predicted from the classical mechanics. Accurate description of quantum dynamics in complex molecular environments requires methods that are general enough to represent realistic interaction potentials and efficient enough to be able explore vast parameter space constituting the ensemble of systems. Path integral formalisms and quantum master equation approaches are two attractive and successful tools that have been used to this end. The Jang group is focused on making these theoretical and computational tools theoretically more reliable and versatile.
Energy on earth begins with photosynthesis, the first step of which is the light harvesting process, namely, the capture of solar photons and the conversion of their energy into the form of electronic excitation energies of pigment molecules. Various photosynthetic organisms have evolved surprisingly diverse light harvesting complexes with different characteristics while utilizing a fairly small set of pigment molecules. The quantum efficiency of these light harvesting complexes are remarkably high, roughly being 90% or higher. The diversity of light harvesting complexes comes largely from different spatial arrangements of pigment molecules and delicate tuning of their excitation energies and mutual electronic couplings by surrounding protein environments. Understanding the design principles of the light harvesting complexes is a theoretical issue with many implications, in particular, for the development of genuinely biomimetic solar light harvesting systems. The Jang group has been particularly interested in modeling the spectroscopy and the dynamics of excitons in light harvesting complexes from purple bacteria, and has uncovered important effects of quantum delocalization, disorder, and hydrogen bonding in these systems.
The dynamics of excitons and charge carriers (electron/hole) have significant implications for energy conversion, sensing, and imaging. The Jang group has been interested in constructing novel and well-defined Hamiltonian models for these processes combining the data available from large scale calculations and experimental measurements in a consistent manner, and to use the models to explain or predict experimental results. A progress in this direction is being made for systems of organic molecules with potential applications to solar energy conversion.
How olfaction works at molecular level remains largely a mystery at this point, for which a wide range of theories and models have been proposed. The Jang group is interested in genuine molecular level understanding of how olfactory receptors are activated by odorants. Development of theoretical models and computer simulations are currently being pursued to this end.
© 2018 The Jang Group, Chemistry Department, Queens College, CUNY.