Site dependence of surface dislocation nucleation in ceramic nanoparticles

The extremely elevated strength of nanoceramics under compression arises from the necessity to nucleate highly energetic dislocations from the surface, in samples that are too small to contain pre-existing defects. Here, we investigate the site dependence of surface dislocation nucleation in MgO nanocubes using a combination of molecular dynamics simulations, nudged-elastic-band method calculations and rate theory predictions. Using an original simulation setup, we obtain a complete mapping of the potential dislocation nucleation sites on the surface of the nanoparticle and find that, already at intermediate temperature, not only nanoparticle corners are favorable nucleation sites, but also the edges and even regions on the side surfaces, while other locations are intrinsically unfavorable. Results are discussed in the context of recent in situ TEM experiments, sheding new lights on the deformation mechanisms happening during ceramic nanopowder compaction and sintering processes.

Automated summary

The study reveals that in MgO nanocubes, not only the corners but also the edges and side regions are favorable sites for dislocation nucleation, while other locations are inherently unfavorable. This sheds new light on the deformation mechanisms during ceramic nanopowder compaction and sintering processes, based on recent in situ TEM experiments.