Our goal is to develop a molecular level understanding of some of the chemistry that occurs on surfaces. We do this by exploring, theoretically, a number of reactions that are important in catalysis and other surface processes. We use electronic structure methods to compute the molecule-surface interactions, exploring transition states and reaction paths. Both quantum and classical mechanics are then used to examine the reaction dynamics.
A first step in many important catalyzed reactions is dissociative adsorption, where a molecule breaks a bond as it collides with and adsorbs onto a surface. We have studied the dynamics of the dissociative adsorption of H2, N2 and CH4 on a variety of metal surfaces, and plan to examine similar reactions for CO, CO2 and H2O. We are interested in understanding how reactivity varies as a function of the translational, rotational and vibrational energy of the molecule, the surface temperature, and the details of the molecule-metal interaction. In a similar fashion we have examined Eley-Rideal reactions, where particles incident from the gas-phase can react with species already adsobed onto a surface. We have found that the incident particles often trap onto the surface, forming highly mobile and reactive “hot” precursors. We have also explored the details of how molecules stick onto surfaces, and how H atoms migrate through the bulk of metals.
Our work often involves the development of new methodologies. For example, we have devised and implemented several techniques for evolving the molecular wavefunction in time, allowing us to follow the evolution of a surface reaction quantum mechanically. Much effort has also been spent developing methods for coupling the reacting molecules with the thermal vibrations of the metal lattice, allowing us to study how the temperature of the metal effects reactivity.