Quantum Chemical Dynamics

In many chemical systems, outcomes are dependent on the tendency of a combination of atoms to associate (in, for example, a chemical compound) or dissociate (into constituent atoms available for new reactions). In many such systems, the molecules are "metastable," requiring only a small addition or loss of energy to dissociate or combine. Exact prediction of rapid chemical dynamics requires quantum physics approaches because of the small spatial scales of the events.

The traditional computational approach to these dynamics relies on algorithms to solve the time-dependent Schrödinger equation, which describes how the wavefunction of a physical system (such as a dissociating molecule) evolves over time. Often the relevant equation system is solved on very large fixed grids, but these methods are not straightforwardly extensible to many-atom systems. Professor Wyatt's approach, by contrast, derives from a distinct formulation of quantum mechanics called "quantum hydrodynamics." This way of formulating such problems was developed in detail by physicist David Bohm in the early 1950s, but computational methods for it were not found until Wyatt and others began to work on the problem in the late 1990s.

Wyatt and student Courtney Lopreore (now at the Salk Institute in La Jolla, California) developed a method that solves the equations of motion to find quantum "trajectories" or paths for the units of the system (atoms or combinations), which are treated as "fluid particles." The "fluid" in this picture is the quantum probability density (the probability of finding an atom at one distance or another from another atom), discretized into small "particles." A typical simulation displays the dance of these particles and illustrates the tendency of the system to remain intact or dissociate under varying conditions.

For a more detailed description of the project, see "Robert Wyatt's New Approach to Fundamental Problems in Quantum Chemistry."