Speaker:Richard Otis, Pennsylvania State University
Title: Global energy minimization of multi-component phases with internal degrees of freedom

Abstract: In computational thermodynamics, miscibility gap detection is a crucial feature to accurately calculate the energy of phases containing regions of instability, i.e., spinodals, and is commonly handled through global minimization (GM) of the Gibbs energy. While many authors have outlined methods for either the two-component or two-phase cases, few examples of multi-component GM methods exist in the literature. Here we develop an approach that treats a phases internal degrees of freedom as its primary variables. Composition space is quasi-randomly sampled using an N-dimensional Halton sequence and the minimum energy surface is computed using the QuickHull convex hull algorithm. Tie hyperplanes spanning miscibility gaps and/or multi-phase regions are identified by facet projection along each composition axis. A software implementation, provided in the open-source Python library pycalphad, is discussed within the broader context of interactive scientific computing.

Time: Friday, February 6, 2015, 1:30-2:30 p.m.

Place: Exploratory Hall, Room 4106

Department of Mathematical Sciences
George Mason University
4400 University Drive, MS 3F2
Fairfax, VA 22030-4444
http://math.gmu.edu/
Tel. 703-993-1460, Fax. 703-993-1491