Ab initio calculations of strain fields and failure patterns in silicon nitride intergranular glassy films

Abstract

Theoretical experiments were performed on silicon nitride intergranular glassy film (IGF) models subjected to tensile loading using an accurate ab initio method. The results were used to investigate the strain fields within IGF models. The Green–Lagrange strain fields were calculated from the displacement gradients of the IGF models under various loads. Significant deviations from the first-order Cauchy–Born rule were observed for IGF models even under small load. The strain fields were also analysed to understand atomic-scale mechanisms that lead to intergranular and intragranular failures.

Acknowledgments

This work is supported by the US DOE under Grant NO. DE-FG02-84DR45170. This research used resources of NERSC supported by Office of Science of DOE under contract No. DE-AC03-76SF0098. AM is partially supported by NSF grant CMS-0506297.