Molecular dynamics simulation of structural changes in single crystalline silicon nitride nanomembrane

AK Shargh and N Abdolrahim, CERAMICS INTERNATIONAL, 45, 23070-23077 (2019).

DOI: 10.1016/j.ceramint.2019.07.355

We use atomistic simulations to investigate the mechanical behavior as well as the structural changes of single crystalline beta-Si3N4 nanomembrane upon tensile loading. Our results suggest that upon loading along (1) over bar2 (1) over bar0, the nanomembrane exhibits two distinct elastic behavior with varying Young's modulus and almost zero plasticity until fracture. We found that the variation in Young's modulus attributes to the change of crystallographic structure. Upon introduction of N-Si-N bond angles into three main types we were able to explicitly distinguish these structural changes. We further showed that upon tensile loading along (1) over bar 010 the nanomembrane behaves the same way with two elastic regimes, while a small plastic deformation is also observed up to the fracture. The post processing analysis reveals that plasticity is proceeding upon strain localization into shear bands within the slip system. The zero plastic deformation upon loading along (1) over bar2 (1) over bar0 is due to the zero Schmid factor.

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