Tensile mechanical properties of c-BN thin layers under tension: A molecular dynamics simulation

Molecular dynamics simulations were performed to investigate the axial tension properties and fracture mechanisms of the c-BN nano thin layers. It is found that thin layers display a linear stress-strain relationship firstly at ε < 0.054, and then a quasi-linear response at 0.054 < ε < 0.302, and finally the stresses decrease gradually until entire fracture occurs. Fracture stresses are 76, 49, 33 and 21 GPa, respectively, for 100 K, 300 K, 500 K and 700 K, and Young's modulus decreases gradually with the increasing of temperature. The deterioration in mechanical properties derives from the formation of major defects that B[sbnd]N bond, tetragonum and octagon with broken bonds, and two-hexagon by the sharing of the nitrogen atom. The results not only clear the outstanding property of c-BN nano thin layers but also built relevance between the mechanical behaviors and loading conditions such as side length, temperature and strain rates.