Title: Evaluating Continuum Mechanical Quantities at the Atomic Scale

Presenter: Jonathan Zimmerman

Affiliation: Sandia National Laboratories

Abstract: Continuum theory is commonly used to analyze the mechanics of materials and structures. However, it is often advantageous to use atomistic modeling and simulation methods to gain insight on phenomena such as deformation leading to the creation of material defects and the transport of energy in materials. While these methods can provide a wealth of information, clear connections between nanoscale mechanics and engineering scale analysis need to be made. Among the many efforts to derive expressions for calculating continuum variables within an atomic system is the work by Hardy (1982), who used averaging volumes and weighting functions associated with fixed spatial points within the continuum Euler balances of mass, momentum and energy. An alternative approach is to construct a similar formulation to Hardy's in the reference or material frame. I will present work done to implement such expressions for Lagrangian and Eulerian analysis of material deformation into LAMMPS’ USER-ATC package, and will touch on several examples that use this capability, such as studying the plastic deformation of nanocrystalline metals, verification of inter-atomic potentials used to simulate the shock response of materials, and application of the continuum J-integral – a metric used to quantify the energetic driving force for crack propagation and defect motion – at the nanoscale.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04- 94AL85000.