Physical Chemistry Seminar: Professor Baron Peters, UC Santa Barbara (Host: Tom Markland)
"Theoretical and computational advances in solute precipitate nucleation"
Nucleation refers to an activated process by which the first stable embryo is born to initiate a phase transition. I will present three vignettes from our efforts toward prediction, control, and extraction of nucleation rates from data. Part I will provide background on theories and methods for studying nucleation. I will highlight the special challenges posed by solute precipitate nucleation and show how these are being overcome with seeding methods. In practice, nucleation is difficult to understand and/or control because rates are usually dominated by heterogeneous sites with unknown characteristics. Parts II and III present two strategies to promote the more predictable and controllable kinetics of homogeneous nucleation. Part II considers trace additives that modulate nucleation rates in many natural and industrial environments. We combine classical nucleation theory and an adsorption theory to understand how trace additives can accelerate nucleation. The theoretical predictions are tested against simulations of a Potts-lattice gas model with solvent, solute, and surfactant-like species. Part III examines La Mer burst nucleation, where all of the individual nucleation events occur en masse and quasi-simultaneously. A simple model shows that the average resulting nucleus size is largely determined by the solute supply and growth rates, with details of the nucleation kinetics being surprisingly unimportant. However, the shape of the particle size distribution moments after the burst provides a record of the nucleation kinetics. These conclusions remain true for more elaborate models of La Mer burst nucleation, and they provide an exciting route to homogeneous nucleation kinetics from experiments.
About the Speaker
Baron Peters (1976 - ) is from Moberly, Missouri. He completed a B.S. in Chemical Engineering and a B.S. in Mathematics at the University of Missouri - Columbia. He studied catalysis and reaction rate theory for a PhD with Alex Bell and Arup Chakraborty at the University of California - Berkeley in 2004. He then worked as a post-doc with Bernhardt Trout at the Massachusetts Institute of Technology, and with Berend Smit at the Centre Europeen de Calcul Atomique et Moleculaire (CECAM). Baron is currently a professor in the Department of Chemical Engineering and in the Department of Chemistry and Biochemistry at the University of California - Santa Barbara. Baron has contributed several leading computational methods and theories for understanding chemical reaction rates, heterogeneous catalysis, and nucleation kinetics. Baron also authored “Reaction Rate Theory and Rare Events”, the first comprehensive textbook on reaction rate theory and rare events methods.