|Phase-field crystal modeling of deformations and phase transformations at the nanoscale |
|Mikko Haataja, Princeton University|
12:10 PM, CCR 201
The vast majority of naturally occurring or synthetic materials are not in equilibrium and contain complex spatial structures on nanometer, micrometer or millimeter length scales. This is particularly important since these morphologies often determine the mechanical, electrical, and optical properties of the material. Traditionally, the temporal evolution of morphologies has been modeled through numerically solving either a set of physically-based sharp-interface or diffuse-interface (“phase-field”) models. While such approaches have proven to be very useful in elucidating the physics behind the evolving morphologies in, e.g., phase transformations and thin film growth, incorporating plastic effects and other atomistic features in these models becomes quite cumbersome. As an alternative approach, in this talk I will describe a simple continuum model which is capable of modeling both elastic and plastic deformation under non-equilibrium conditions. This so-called “phase-field crystal” method introduces a continuous atomic mass density field in which fast atomic vibrations have been integrated out. The free energy functional of the system supports spatially periodic states, and naturally incorporates elastic and plastic effects, grain boundaries, free surfaces, and arbitrary crystal orientations. Wave-like dynamics with dissipation can be constructed to govern the temporal evolution of the density field across mesoscopic time scales, inaccessible by direct Molecular Dynamics simulations. I will illustrate the utility of this approach with specific examples from deformation of nanocrystalline materials, ultrathin film growth and deformation of ferroelectric nanomaterials.
Bio: Dr. Haataja is a graduate of Tampere University of Technology (Finland) and obtained his PhD in Theoretical Condensed Matter Physics at McGill University (Montreal, Canada). He has been an Assistant Professor at the Mechanical and Aerospace Engineering Department at Princeton University since 2004. Dr. Haataja‘s research interests range from the mechanical behavior of metals and alloys to the self-assembly of soft materials and evolving microstructures in biology. His research has been sponsored by NSF and AFOSR.
Host: Adrian Mann 732.445.8421