Multimillion-atom molecular dynamics simulations have been performed on parallel computers to study atomistic mechanisms of nanoindentation of nanocrystalline ceramic thin films, understanding of which is critical for the design and fabrication of nanocrystalline materials with enhanced mechanical properties. We have implemented a sintering scheme involving high pressure and high temperature to create a realistic two-phase microstructure with crystalline grains and a disordered intergranular phase. We have found that the increased volume fraction of highly disordered intergranular films manifests itself in novel deformation mechanisms as compared to nanometals. Simulation results on nanocrystalline silicon carbide show that the interplay between grain rotation, cooperative grain motion, sliding at grain boundaries and integranular deformation combine to produce a unique load-displacement response. We predict a crossover from continuous cooperative grain response to discrete intra-grain plasticity at a critical depth that is a fraction of the grain size.

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