quantum-classical treatment of condensed phase proton transfer.
Published: 2006
Language: eng
Number of pages: 130
ISBN-13: 9780494217832
Description: The study of quantum rate processes occurring in condensed phase environments is difficult because of the large number of degrees of freedom involved. Since a full quantum mechanical treatment is not computationally feasible, one is motivated to take a mixed quantum-classical approach. This approach is applicable when one can single out a few degrees of freedom to be treated quantum mechanically while treating the remainder classically. We describe a method that is based on the quantum-classical Liouville equation, which clearly prescribes the details of the coupling between the quantum and classical degrees of freedom.Starting from the reactive-flux correlation function expression for the quantum mechanical rate coefficient of a general reaction   A&rlhar2;B , we derive a quantum-classical rate formula which is amenable to the simulation of condensed phase quantum rate processes. This formula involves quantum equilibrium sampling and propagation of chemical species variables in time based on the solution of the quantum-classical Liouville equation. This nonadiabatic dynamics algorithm prescribes evolution on single adiabatic surfaces and on the mean of coherently coupled pairs of adiabatic surfaces.A more realistic model of a proton transfer reaction in a linear hydrogen-bonded complex dissolved in a polar solvent is also studied. The rate and mechanism of the reaction are investigated using both adiabatic and nonadiabatic dynamics and the role of the coherently coupled surfaces in the nonadiabatic dynamics is elucidated. This study constitutes the first application of quantum-classical Liouville dynamics and our quantum-classical rate theory to a realistic, large-scale system.Factors influencing the rates of quantum mechanical particle transfer reactions in many-body systems are investigated. The investigations are carried out on a simple proton transfer model that captures generic features seen in more realistic models. The model involves a bistable quantum oscillator coupled to a one-dimensional double-well reaction coordinate which is in turn coupled to a bath of harmonic oscillators. Reaction rates are shown to be influenced significantly by both the quantum equilibrium structure and nonadiabatic dynamics. Nonadiabatic dynamcal effects are found to play the major role in determining the magnitude of the kinetic isotope effect for the model transfer reaction.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0307.

Thesis (Ph.D.)--University of Toronto, 2006.

Electronic version licensed for access by U. of T. users.