Modeling of atomistic scale shear failure of Ag/MgO interface with misfit dislocation network

Metal/ceramic interfaces have broad applications and misfit dislocation network (MDN) is a prominent feature of the equilibrium metal/ceramic interfaces. As one main failure mode, interface shear failure is strongly affected by the motion of MDN. In this work, we investigate the equilibrium interface structure and shear failure of Ag/MgO interface via atomistic simulation method. Periodically distributed in-plane strain field caused by MDN and severe strain concentration at dislocation node regions are found by strain analysis. During interface shearing, these dislocation nodes act as strong pinning points to the gliding motion of MDN, which leads to bending of dislocation lines. Besides, energy analysis shows the interface shear stress is largely dependent on the variation of misfit dislocation energy. To understand interface shear failure under more complex conditions, we study the effect of model thickness and shear direction further. Due to transformation of nodal structure, the shear strength of thick model eventually decreases by almost a quarter; shear failure along the direction of Burgers vector is found to be energetically favored, with the lowest interface shear strength. This work reveals the crucial role of MDN in interface shear process, and the theoretical understanding gives some hints to metal/ceramic interface design