Electronic Energy and Charge Transfer Dynamics via Quasi-Classical Methods
Liu, Yudan
2023
Abstract
Electronic energy transfer and charge transfer processes play crucial roles in many photochemical processes. Computational studies on these processes are challenging subjects in the chemistry community. The problem arises from the prohibitive computational costs of the quantum-mechanically exact methods for these typically large systems. Developing methods that can handle such large dimensionality is then the key priority. In Chapter I of this dissertation, the motivation for studying the energy transfer and charge transfer processes will be laid out. Next, a literature review of current theoretical approaches to handle these problems will be discussed. In Chapter II, the quasi-classical mapping Hamiltonian (QC/MH) methods will be laid out with various mapping schemes. The dynamics of the four types of two-state spin-boson models generated with QC/MH methods will then be compared to the exact results. By this benchmarking of accuracy, it will be shown that the modified LSC produced the most accurate simulation results. One version of modified LSC will be shown to even have the capability to generate accurate simulation results for systems in low temperature. In addition, it will be demonstrated that even with the same method, the simulation accuracy can differ for different electronic observables. The results will emphasize the importance to evaluate all elements of electronic density matrix for method benchmarking. In Chapter III, the generalized quantum master equation (GQME) with a general choice of projection operators will be presented, along with a walkthrough of their application procedures. The assessment of the accuracy of GQME will then be completed with two-state spin-boson model. It will be shown that the best approach for GQME is to perform population-only reduced-dimensionality GQME in the observable representation. This combination of approaches will provide the most cost-efficient and accurate simulation. In Chapter IV, the application of QC/MH methods and GQME is furtherly demonstrated with the linear vibronic coupling (LVC) model. We will then discover that the performance of QC/MH methods on LVC models might not agree with the performance of spin-boson models. This will suggest that accuracy benchmarking should be performed not just on spin-boson model, but on LVC model as well. In Chapter V, the energy transfer process in Fenna-Matthews-Olson(FMO) complex will be studied with the QC/MH and GQME. The simulation results will show that combining QC/MH with GQME allows one to generate accurate simulations even for large and complex systems. This discussion will expand our application of QC/MH and GQME beyond two-state systems. In Chapter VI, the various ways to generate the time evolution operators using the GQME, which can be used along with quantum computing algorithms to propagate the system, will be discussed. A comparison between different approaches will then be discussed, and we will find out that the best approach is to directly generate the propagator through GQME. In Chapter VII, we will present a summary of the discussions. In addition, further directions for QC/MH and GQME will be presented. This includes applying QC/MH and GQME to wider range of systems and further development on the reduced-dimensionality Condon approximation GQME.Deep Blue DOI
Subjects
charge transfer electronic energy transfer quantum dynamics quasi-classical mapping hamiltonian generalized quantum master equation quantum computing
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