MSE Seminar Series: Talid Sinno
Friday, November 11, 2011
Room 2110 Chemical and Nuclear Engineering Bldg.
301 405 5240
Atomistic Simulation and Analysis of Microstructure Evolution in Crystalline Materials
Department of Chemical and Biomolecular Engineering
University of Pennsylvania
The atomistic analysis of crystalline material properties is often complicated by high temperature entropic effects that can lead to significant deviations from ground state predictions. Using crystalline silicon as a model material, a theoretical/computational framework for thermodynamic analysis of crystalline microstructure is presented. The essence of the approach is to map out a portion of the energy landscape associated with a phenomenon of interest, and then use the landscape features to probe key mechanisms.
We consider two primary situations to demonstrate the utility of this approach. First, the physics of point defect clustering at elevated temperature is addressed. Defect clusters, such as nanovoids and self-interstitial precipitates, play important roles in establishing the quality of crystalline silicon for both microelectronic and photovoltaic applications. We show how entropic contributions arising from vibrational and configurational degeneracy lead to subtle but important changes in the thermodynamics of these species. In the latter part of the presentation, the phenomenon of crystal melting is addressed. Here, it is shown that the energy landscape framework provides a powerful setting for analyzing the microscopic mechanisms of melting. In particular, we consolidate melting behavior in several different geometries and show how interfacial curvature influences melting at the atomic scale.