Atomistic simulation study on the shear behavior of Ag/MgO interface

Metal-oxide composites with advanced mechanical properties play an important role in many practical applications, and failure of the metal-oxide interface is directly related to service life of related structures. In order to understand interface failure mechanism, study on atomic-scale separation of metal-oxide interface is significant. In this work, shear behaviors of Ag/MgO (0 0 1) coherent interface and semi-coherent interfaces are studied by employing molecular mechanics method, and some interesting size and defect effects are found. The simulation results show that interface shear stress and displacement appear periodic characteristics with loading. For coherent interface, the interface shear stress and displacement both increase first in each period, then the shear stress drops abruptly after reaching ideal shear strength, and the shear displacement jumps by a unit cell length. The shear strength keeps a constant for all periods. Atomistic simulations of interface systems with different thicknesses show size-independent shear strength and intrinsic interface adhesive energy, but needed loading displacement for the first jump of interface displacement is larger for the thicker systems due to the larger energy consumed by bulk materials. For both 1D and 2D semi-coherent interfaces with dislocations, the shear strength is more than one order of magnitude lower than the ideal shear strength, and the interface displacement changes more continuously with decreased period, which is attributed to different shear mechanism related to dislocation gliding. Comparing 2D semi-coherent interface with 1D case, the shear strength and energy barrier of dislocation motion are both higher due to pinning effect of dislocation intersections.