Atomistic quantum dynamics: implementation and applications of the quantum-classical path integral method

Understanding reactivity is a central goal of chemical physics, and investigations in the condensed phase are particularly important for many applications, including biochemical cycles and materials science. However, theoretical progress toward an improved understanding of chemistry in such environments can be hampered by the need for both a quantum mechanical treatment for the reactive degrees of freedom, along with a classical description of the environment, since it is typically too complex for quantum dynamical simulation to be feasible. To address these difficulties, a number of mixed quantum-classical methods have been proposed, beginning with averaged-force approaches in the earliest days of quantum theory and continuing through many new variations and improvements. Unfortunately, owing to the differences between quantum and classical mechanics, most such methods must resort to ad hoc assumptions in order to successfully combine the quantum and classical degrees of freedom in a unified description. Recently, our group has started from the path integral formulation of quantum theory and derived a completely rigorous mixed quantum-classical method, which requires no ad hoc elements and can be applied to arbitrary solvent environments. In this work, the quantum-classical path integral approach is described, along with many of the improvements to the theory which allow it to be efficiently applied to simulation of large chemical systems. As specific examples of the power of the method for atomistic simulation, application to the Azzouz-Borgis model of proton transfer is discussed, along with results from the simulation of electron transfer in a bacterial photosynthetic reaction center. Strategies for connecting simpler harmonic models to fully atomistic molecular dynamics simulations are also considered and discussed in the context of extending the domain of rigorous quantum dynamical simulations to challenging problems of contemporary interest.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2016

Author dc:creator

• Allen, Thomas Carlton

Contributors dc:contributor

• Makri, Nancy
• Hammes-Schiffer, Sharon
• Hirata, So
• Wagner, Lucas

• Quantum Dynamics
• Charge Transfer

Statement dc:rights

• Copyright 2016 Thomas Allen

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/92820

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/92820