Date of Award
Program or Major
Doctor of Philosophy
Howard R Mayne
The interaction of gas phase species with surfaces plays an important role in a myriad of processes such as heterogeneous catalysis, corrosion and the etching of semiconductor surfaces in the microelectronics industry. Thus, the study of gas-surface interactions has become a field of intense research. In this dissertation, we present the results of a computational study of the scattering of gas phase molecules and van der Waals clusters from surfaces. We have used molecular dynamics calculations which allow for the examination of the microscopic details of gas-surface scattering.
In this work we study four distinct systems. In Chapter I the focus is on the scattering of van der Waals clusters of N$\sb2$ from crystal surfaces. We find that the cluster-surface scattering dynamics are very different from those observed in monomer-surface scattering. Furthermore, our results are in qualitative agreement with a recent experimental study of the scattering of nitrogen clusters from metal surfaces.
The focus of Chapter II is on the effect of reagent rotation and rotational alignment on the dissociative chemisorption of H$\sb2$ on metal surfaces. We find that the probability of dissociative chemisorption depends strongly on both the rotational energy and the plane of rotation of the reactant H$\sb2$. Our results suggest that such information might be useful in uncovering intricate details of the potential energy surface governing these reactions.
In Chapter III we examine the dissociative trapping of HD on a tungsten surface. In dissociative trapping only one atom becomes bound to the surface while the other returns to the gas phase. We observe a novel isotope effect in this channel which is explained in terms of a simple mechanism for the dissociative trapping process.
Finally, in Chapter IV we examine the effect of dissolving an H$\sb2$ molecule in an argon microcluster on the dissociative chemisorption of H$\sb2$ on a silicon surface. We find that this does, in fact, facilitate the reaction. We also find that the probability of reaction is greater when the H$\sb2$ occupies a site on the "outside" of the cluster as opposed to "inside".
Beauregard, John Norman, "The scattering of gas phase molecules andvan der Waals clusters from surfaces" (1993). Doctoral Dissertations. 1746.