Dynamics behavior and defects evolution of silicon nitride nanowires under tension and compression load: A molecular dynamics study

Molecular dynamics simulations are used to investigate the dynamics behavior of single-crystalline β-Si3N4 nanowires with different aspect ratios under tension and compression load. Results show under tension deformation the elastic limit is independent of aspect ratios and occurs around ε = 0.05. The calculated breaking strength increases with the decrease of aspect ratios of nanowires under tension and compression load. In addition, the deformation mechanism is discussed in details based on the snapshots of defects evolution. The mechanism of failure by fracture preceded by plastic deformation is present. Large numbers of defects that Si–Si bonds and spheric cluster-like N atoms can be observed under tension deformation. Under compression deformation other newly-developed defects such as fourfold bonds of Si atoms appear in the middle part of the lower surface and two symmetric parts of top surface, which lead to primary stress concentration, together with substantive twofold and threefold Si atoms defects, come into being a maximum value of stress. This study on the dynamics behavior of nanowires will be conducive to further understanding of the mechanical properties of nanomaterials.

► The elastic limit is independent of aspect ratios and occurs around ε = 0.05. ► The mechanism of failure by fracture preceded by plastic deformation is present. ► Defects that Si–Si bond and spheric cluster-like N atoms can be observed. ► Defects such as fourfold bond of Si atoms appear under compression.