Goodyear Group Research Synopsis:
The common theme in the research performed by the Goodyear group is a focus on understanding the many-body, collective nature of liquids and fluids. (Familiar examples of important collective effects in the solid state are phonons, collective vibrational modes of a crystal, and metals, which arise from a collective overlap of atomic orbitals that manage to span the entire crystal.) Unlike in crystals, however, where the collective effects are indeed important, but nonetheless rather straightforward to enumerate, the inherently disordered nature of liquids and fluids makes an analysis of collective effects quite challenging. To date, it remains impossible (for all but the simplest liquids) to accurately predict under what conditions a liquid will conduct electricity.
One project that fits into the above rubric is our study of the microscopic mechanisms by which transition state theory is violated. Transition-state theory, by itself, already incorporates collective solute-solvent energetics. It fails, however, because the dynamics predicted by the theory neglect dynamical coupling between the solvent and the solute(s). We are using Instantaneous Normal Modes to let us probe which collective solute-solvent motions (which modes) are most important in causing violations of transition state theory. In effect, we are monitoring, at the atomic level, solvent participation in the reaction, thereby giving us a handle on the role that the solvent plays in the reaction mechanism.
Another project involves using mixed quantum-classical simulations to probe the effect of polarizability on the dynamics of hydrated electrons.
Additional projects include a study of supercritical fluids near the critical point, where collective density fluctuations cause the fluid to be inhomogenous on a mesoscopic scale, and work on the electronic structure of liquid semiconductors - under what conditions of temperature and pressure are they semiconductors, or metals, or insulators? In all cases the projects involve a combination of analytical (paper-and-pencil) techniques and computer simulations (molecular dynamics or Monte Carlo).