MSE/ME Special Seminar on Computational Materials Science and Materials Modeling - Md Zubaer Hossain
Thursday, April 4, 2013
Rm. 1105, Jeong H. Kim Engineering Bldg.
301 405 4799
Multiscale Implications of Nanoscale Heterogeneity & Deformation in Solids
M. Zubaer Hossain
Division of Engineering and Applied Science
California Institute of Technology
Pasadena, CA 91125
When a solid is exposed to a source of higher energy (e.g. Sun, or an AFM tip) or deformed mechanically, its fundamental constituents atoms, electrons, and phonons respond in an intricate manner and transport energy. Likewise, nanoscale deformation or heterogeneity couples strongly with the associated energetic processes and governs the solids macroscopic ability to store or transfer energy in structural, electronic, or thermoelectric applications. However, it remains a nontrivial task to investigate the coupling, particularly over a wider range of length or time scales and material conditions, using conventional computational techniques (such as first-principles calculations, molecular dynamics simulations, or the finite element method all of which are mostly constrained at the single level scale or phenomenon).
This talk will discuss a multidisciplinary computational approach to transcend the traditional boundaries of atomistic or continuum calculations in unraveling the critical mechanisms that arise on the nanoscale but affect material properties or processes on the macroscale. The significance of the approach will be exemplified for Si1-xGex systems (quantum dots, quantum heterostructures, alloys), carbon allotropes (graphene, carbon nanotube), and transitional metals (tungsten, tantalum). Particular emphasis will be given to discuss two multiscale modeling efforts: one in the space domain that combines the density functional theory, the k.p method and the finite element method to study the influence of nanoscale heterogeneity on energy absorption in alloy quantum dots; and the other in the time domain that links molecular dynamics with the mechanics of surface height evolution to study the effect of femtosecond energy deposition on ripple formation in semiconducting solids. Results reveal a novel variable for modulating electron confinement in nanostructured materials with applications in solar energy or spintronics, and a mechanism responsible for causing instability during nanofabrication of electronic devices.