The objective of the research of my group is a theoretical understanding at the molecular level of dynamical processes such as energy transfer and chemical reaction at surfaces, in condensed-phases and in biological environments. We work on developing novel theoretical and computational tools and applying the tools to elucidate experiments.

Theories of chemical reaction dynamics are usually based on two assumptions. The first is the Born-Oppenheimer approximation: electrons adjust instantaneously to the slower movement of atoms, so that the atoms can be considered to move along a "potential energy surface" derived from a single electronic state. The second assumption is that the atomic motion can be described by classical mechanics.

These assumptions form the basis of the conventional "molecular dynamics" computer simulation method. However, one or both of these assumptions are invalid for many important dynamical processes. Breakdown of the Born-Oppenheimer assumption is the rule rather than the exception in electron transfer, photochemistry, and reactions at metal surfaces. Classical mechanical treatment of atomic motion is inadequate in situations such as proton transfer where quantum mechanical zero-point motion or tunneling effects dominate.

While a full quantum mechanical treatment of electronic and atomic motion would be desirable, this is impractical at present except for the very simplest chemical systems. Thus, to realistically describe complex systems, we seek to develop methods for introducing the most crucial quantum mechanical effects into an otherwise classical molecular dynamics framework and to include self-consistent feedback between the quantum and classical degrees of freedom. These methods show promise of greatly extending the range of validity of the molecular dynamics approach while retaining its advantages: practicality, applicability to complex systems, and the ability to "watch" the motions of individual atoms on the computer screen as they participate in a chemically reactive event.

These techniques can be applied fruitfully in various fields. They reveal the rates and pathways of energy flow in condensed phases and at surfaces, which are frequently the controlling factors in materials processing and catalytic reactions. They are useful in studying electron transfer reactions in liquids or at the liquid-solid interface as well as electron and proton transfer reactions in biological systems. They enable the exploration of competition between thermal and non-thermal reaction pathways in photochemistry, including transformations induced by high power lasers.

Our objective is not merely to reproduce experimental results but to uncover the underlying mechanisms by answering the question: why did the experiment turn out the way it did? In addition, our approach allows us to examine behavior that cannot be studied experimentally and to make quantitative predictions that will provide guidance to experimentalists when designing experiments.

Selected Publications

"Electron-Hole Pair Contributions to Scattering, Sticking and Surface Diffusion: CO on Cu(100)", J. T. Kindt, J. C. Tully, M. Head-Gordon and M. A. Gomez, J. Chem. Phys., 109, 3629 (1998).

"Mixed Quantum-Classical Dynamics", J. C. Tully, Faraday Disc. Chem. Soc., 110, 407 (1998).

"Perturbed ground state method for electron transfer", O. V. Prezhdo, J. T. Kindt  and J. C. Tully, J. Chem. Phys., 111, 7818 (1999).

"Nonadiabatic Dynamics via the Classical Limit Schrodinger Equation", J. C. Burant and J. C. Tully, J. Chem. Phys. 112, 6097 (2000).