Fracture behavior of ordered and disordered solids predicted by atomistic simulations

Crack initiation and propagation start at the atomic level but can lead to material failure. The mechanical response of a solid, brittle or ductile, therefore depends on the type of bonding and degree of order and disorder. However, from an engineering perspective, predicting the stress–strain response of various solid materials remains highly challenging. Building on molecular dynamics simulations, we here investigate these phenomena at the atomic scale in both ordered (crystalline) and disordered (glassy) solids with bonding types covering covalent, metallic, ionic, coordination, and hydrogen bonding. We demonstrate that stress accumulation and release are inherently tied to the change in the atomic volumes of the atoms in both the ordered and disordered solids. Based on this, we propose a universal model for predicting the microscopic fracture behavior. Specifically, the stress–strain response can be predicted by the loading-induced atomic volume change combined with an energy-related constant that is related to the bonding type. The model is applicable to a wide range of solid materials, and thus elucidates the intrinsic relation between the mechanical behavior and atomic-scale features, offering a new tool for atomistic design of strong and tough solid materials.