Analysis of global instability mode in atomistic model
Yoshitaka Umeno (The University of Tokyo), Wolfram Noehring (), Albert Iskandarov (), Atsushi Kubo (), Erik Bitzek ()
Instability in Solids and Structures
Tue 10:45 - 12:15
Barus-Holley 190
To fully understand the deformation and fracture in solid material, the mechanism of structural instability at the atomic level must be investigated. Since deformation involves collective motion of atoms, it is required to consider the instability of the entire system (global instability). The instability of an atomistic model can be rigorously evaluated by solving the eigenvalue problem of the Hessian matrix taking into account all the degrees of freedom of the atoms. In this study we have applied this method to the problem of dislocation nucleation and twinning from defects in a metal film under tension using an EAM potential. While slight change in defect structures results in different deformations, a number of localized instability modes are observed, which indicate potential sites of deformation, before instability is realized. In the evolution of eigenvalues with increasing global strain (or stress), we found avoidance of eigenvalue crossing (level repulsion), which seems to be the phenomenon predicted by the von Neumann-Wigner theorem. Relation between potential instability modes and deformation at finite temperature is also discussed.