MIE Seminar Presentation: Computational Materials Science – Applications at a National Laboratory by Dr. Luis Zepeda-Ruiz
~~ The Department of Mechanical and Industrial Engineering Presents
Dr. Luis Zepeda-Ruiz
The Lawrence Livermore National Laboratory
Topic: Computational Materials Science – Applications at a National Laboratory
Date: Monday, April 14, 2014
Time: 10:30am to 12:00pm (Refreshments from 10:00am to 10:30am)
Location: 344 Curry Student Center
Abstract: The development of computational models for the simulation and prediction of the structure, properties and behavior of heterogeneous materials is advancing our understanding of materials science and engineering at an increasing rate. In most cases it requires the use of a variety of computational methods that span from an atomistic description of interactions to a continuum numerical modeling that includes: first principles calculations, structural relaxations, lattice and molecular dynamics, and kinetic Monte Carlo, among others. This is particularly true at a National Laboratory, where research has applications in future energy production, engineering innovations, and national security. In this presentation I will focus on two examples of my research at LLNL: (1) the application of Monte Carlo simulations in the study of shape formation and coarsening that occurs during the storage of crystalline powders and (2) the study of the mechanical response of metallic systems via molecular dynamics. For the first example, starting from an ab-initio description of inter-atomic interactions we develop a simple scheme of generating a short-range on-lattice molecular potential, which is then incorporated into a lattice Monte Carlo code for simulating size and shape evolution of micro-crystallites. We investigate several interesting effects including the evolution of the initial shape of a “seed” to an equilibrium configuration, and the variation of growth morphology as a function of the rate of particle addition relative to diffusion. The second example will show results of the mechanical studies on nanoporous gold (np-Au). The higher-than-expected yield strength seems to be linked to the nanoscale morphology of np-Au which can be described as an open sponge-like network of interconnecting ligaments on the nanometer length scale. Using molecular dynamics simulations of defect-free nanopillars with realistic cylindrical geometries we obtain an atomic-level picture of their deformation behavior under compression and tension. We find that dislocations are nucleated in the two outermost surface layers and depend crucially on the particular arrangement of steps and facets at the surface of the individual ligament.
Brief Bio: Luis Zepeda-Ruiz received his PhD in chemical engineering from UC Santa Barbara in 2000 where he worked with Prof. Dimitrios Maroudas on the study of strain effects on III-V semiconductor compounds. After a postdoc at Princeton University with David Srolovitz he joined the Lawrence Livermore National Laboratory in 2002 where he remains working as a staff scientist at the Physical and Life Sciences Directorate. His research interests are in the area of computational materials science and engineering of a variety of materials, including semiconductors, ceramics, metals, explosives and crystals. His work includes the application of molecular dynamics, molecular statics, Monte Carlo, firstprinciples, and continuum techniques to study materials properties, defects, interfaces, thin films, crystal growth and morphology evolution.
Monday, April 14, 2014 at 10:30am to 12:00pm
Curry Student Center, 344
346 Huntington Avenue, Boston, MA, Boston