Size Effect on the Fracture Strength and Toughness of Nano-cracked CoSb3: A Molecular Dynamics Study

Molecular dynamics simulations are implemented to study the mechanical fracture of CoSb₃ with penetrated nanocracks under the mode-I stress. The crack surface and crack front direction are (100) and [001], respectively. It is found that, at a fixed initial crack length, the fracture strength varies with the sample size, but the calculated value of fracture toughness K_IC, by employing the classical formula of linear elastic fracture mechanics, maintains constant. When the crack is short in length relative to the sample, the variation of the fracture strength with the initial crack length is well fitted mathematically, and the extrapolation shows rationality even up to the macroscale. More general analyses reveal that, the fracture toughness increases monotonically with increasing the initial crack length until reaching the limit, and the increment is particularly noticeable below 36 nm. Furthermore, different atomic configurations at the crack tip are considered, which show an evident influence on the strength of nano-cracked CoSb₃.