The Huo research group develops and applies multi-scale theoretical approaches to investigate the complex reaction dynamics associated with solar energy harvesting and storage processes. We are interested in developing new non-adiabatic quantum dynamics approaches based on real-time and imaginary-time path-integral formalism. Combined with accurate and scalable electronic structure methods, such as quantum-embedding approach, these dynamical tools are then used to investigate ab-initio non-adiabatic dynamics in exciton induced charge transfer dynamics and catalytic fuel generation reactions. These new simulation techniques will allow us to gain a deeper understanding of the fundamental reaction mechanisms and provide design principles that lead to more efficient solar devices.
Path-Integral Method Development
Our group develops theoretical methods that can treat various quantum and classical degrees of freedom on a consistent dynamical footing. In particular, we are interested in developing non-adiabatic quantum dynamics approaches based on real-time and imaginary-time path-integral formalism.
Partial-Linearized path-Integral (PLPI) dynamics is a real-time path-integral based method that uses classical equations of motions to model the quantum dynamics. The explicit forward-backward propagation of electronic DoF and Linearized approximation on nuclear DoF allows for the accurate and efficient simulation of non-adiabatic quantum dynamics.
Ring polymer molecular dynamics (RPMD) is an imaginary-time path-integral based method that uses classical equations of motions to model the real-time dynamics of a quantum system. Further method development incorporates the explicit description of electronic states with mapping representation, in order to simulate the non-adiabatic dynamics with nuclear quantum effects.
Excitation-induced charge separation dynamics
Designing efficient and inexpensive light harvesting systems is a crucial challenge for sustainable solar energy production. Organic photovoltaics as well as reaction center (RC) in Photosystem II (PS II) can efficiently convert solar exictation into separated charges. Understanding the real-time dynamics of the above processes will advance the design of more efficient solar technologies.
To understand the fundamental mechanism for the long range charge-separation dynamics, we combine accurate semi-empirical electronic structure methods with scalable quantum dynamics methods to gain a detailed picture of the exciton induced charge transfer dynamics.
The coupled transfer of exciton and electron produce separated charges in the reaction center of natural light harvesting systems. PLPI is utilized to investigate the detailed mechanism in this process. The results from numerical simulations recover the time separations from initial excitation transfer, to primary charge-transfer and all the way to the final long-range charge-separation. It also reviews additional competing charge separation path and the effects of coupling between the two types of transfer processes.
Catalytic fuel generation processes
Catalytic fuel generation such as hydrogen evolution is a crucial storage step in solar energy utilization. The fundamental understanding of the basic catalytic mechanisms is hampered by both lack of direct experimental probes of the dynamics and the limited accuracy that DFT can provide.
To address these challenges and gain clear understanding of the catalytic mechanism, we combine Wave Function Theory-in-DFT methods with the QM/MM partitioning strategy to explore the dynamics of these reactions.