Mark Tuckerman's Research Interests
Modern theoretical methods have advanced to a point where they can be used to study the microscopic details of complex condensed phase chemical processes. With such methods, it is possible to make predictions that can be verified through experimental techniques such as ultrafast laser spectroscopy, NMR, and neutron scattering and to provide detailed mechanistic information to complement the results of such experiments.
The research carried out in my group focuses on the development of novel theoretical methodology for treating complex chemical systems and the application of these methods to a variety of important problems. One of the most active research areas in the group is the development and application of algorithms for molecular dynamics calculations. The latter is a technique in which the classical equations of motion that describe the time evolution of a system are integrated numerically, leading to a set of atomistic trajectories subject to a given set of external physical conditions. Using statistical mechanical analysis techniques, it is possible to extract both thermodynamic and dynamical information about a system. The molecular dynamics method can also be used in conjunction with "on the fly" electronic structure calculations (the so called ab initio molecular dynamics method) to study chemically active systems and also with imaginary time path integrals to obtain finite temperature quantum mechanical information. Methodology currently being developed in the group includes new canonical and free energy dynamics algorithms and reciprocal-space-based techniques for treating clusters and surfaces.
Using the battery of techniques they have developed, researchers in my group are currently applying the theoretical methodology to one of the most ubiquitous chemical processes, namely proton transfer. Mechanisms of proton transport in liquid water have been elucidated, and thermodynamic and dynamical aspects of intramolecular proton transfer are currently being determined. In addition, studies of the structure of weakly hydrogen-bonded liquids, such as ammonia and methanol, and of solvation of ions in these liquids are being carried out. Another major focus of the group centers on problems of bio-logical importance. Applications include studies of proton migration along hydrogen-bonded "water wires" in biological environments and studies of complexes of the HIV protease with fullerene-based protease inhibitors of the type developed in Professor Schuster's laboratory. Finally, work is currently under way on the development of new molecular dynamics approaches to the protein folding problem, efficient methods for mixed ab initio/ force-field-based calculations, and parallel algorithms and computer programs for both small- and large-scale parallel computing architectures.
FIGURES: A quantum mechanical probability measure called the electron localization function for isolated OH- and a fourfold coordinated OH- complex. The lone pair electrons are not distinct but form a continuous ring in the plane perpendicular to the OH bond axis. This delocalization leads to anomalously high coordination numbers of OH- and similar anions in hydrogen-bonded liquids.