Nonadiabatic electron transfer in the condensed phase, via semiclassical and Langevin equation approach

In this dissertation, we discuss two methods developed during my PhD study to simulate electron transfer systems. The first method, the semi-classical approximation, is derived from the stationary phase approximation to the path integral in the spin-coherent representation. The resulting equation of motion is a classical-like ordinary differential equation subject to a two-ended boundary condition. The boundary value problem is solved using the "near real trajectory" algorithm. This method is applied to three scattering problems to compute the transmission and reflection probabilities. The strength and weakness of this approach is investigated in details. The second approach is based on the generalized Langevin equation, in which the quantum transitions of electronic states are condensed into a linear regression equation. The memory kernel in the regression equation is computed using a second perturbation expansion. The perturbation is optimized to achieve the best convergence of the second order expansion. This procedure results in a tow-hop Langevin equation, the THLE. Results from a spin-boson system validate the THLE in a wide range of parameter regimes. Lastly, we tested the feasibility of using Monte Carlo sampling to compute the memory kernel from the spin-boson system and proposed a smoothing technique to reduce the number of sampling points.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Song, XiaoGeng, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Troy Van Voorhis.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/49751

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/49751