Title: Atomic Level Variation of Elastic Moduli

Speaker: Nicholas Burgess, NECIS Student, Lehigh University        

Date/Time: Tuesday, August 8, 2006, 9:30 am – 10:00 am (PT)

Location: Building 940 Auditorium (Sandia CA), Building 980, Room 95 (Sandia NM)

Brief Abstract: Elastic moduli are measures of the mechanical stiffness and stability of a material, and can be used to predict instabilities.  At very small length scales, materials can no longer be modeled as a continuum with point-wise continuous variations of quantities such as elastic moduli or stress.   In this work, my collaborators and I put forward a method for determining local variations of elastic moduli in a defected material at the atomic level. This method is based on knowing the Lattice Green’s Function for both an undefected and defected system of the same material.  Lattice Green’s Functions are generated using atomistic analysis methods such as Molecular Dynamics or Kinetic Monte Carlo.  The data from this atomistic analysis is then post-processed to generate Green’s Functions, which are in-turn used within Dyson’s Equation to solve for spatial variations of elastic moduli.  Much of the work this summer has been generating and verifying Green’s functions for certain properties such as symmetry, comparison to continuum, and other validations of these functions.  Volume averaging techniques have been investigated as it is conceptually difficult to apply elastic moduli values to atoms.  Future work necessary for success will also be discussed.

CSRI POC: Jonathan Zimmerman, (925) 294-2437