Concurrent Atomistic-Continuum Simulation of Defects in Polyatomic Ionic Materials

Abstract

This chapter reviews a concurrent atomistic-continuum (CAC) method for studying the dynamic behavior of defects in polyatomic materials. The CAC method combines a unified atomistic and continuum formulation of balance laws and a modified finite element method. In this chapter, we show that in the dynamic simulations of strontium titanate (SrTiO3), the CAC method allows the passages of defects, including dislocations and cracks, from the atomistic to the continuum domain without the need for any special numerical treatment. Then the CAC simulation results of the dynamics of defects in single-crystal, bi-crystal, and polycrystalline SrTiO3 are presented. Simulation results show that CAC successfully reproduces crack propagations, dislocation migrations, and the interplay between cracks, dislocations, and grain boundaries in SrTiO3, with a significant reduction in the degrees of freedom compared with atomistically resolved molecular dynamics (MD) simulation. Most importantly, the essential atomistic features of defects, such as the propagation paths of cracks and dislocations, the dissociation of dislocations, the atomic-scale grain boundary (GB) structures, and atomic details for GB interactions with other defects, are retained in the CAC simulations.