Molecular dynamics study of configuration and stability of vacancy clusters in fcc Ag

Abstract

Vacancies may agglomerate to form vacancy Frank loops of different shapes, as observed by transmission electron microscopy in quenched and irradiated fcc metals. The dynamics for the dissociation of vacancy Frank loops and the subsequent evolution of defect nanostructures were explored by means of the molecular dynamics method and displayed by the local crystalline order method. Frank loops of different initial shapes were found to transform to a variety of defect nanostructures: triangle to stacking fault tetrahedra, equilateral hexagon to quasi-heptahedron, and scalene hexagon to various intermediate structures depending on the length of the short side. The formation energies for vacancy Frank loops of different geometries are introduced to categorize various final configurations. Crystallographic analysis and elasticity calculations were performed to elucidate the transform mechanisms in fcc Ag.

Keywords:

• defect structure
• dislocation theory
• metal
• molecular dynamics
• crystallography
• energetics