Atomistic simulation of temperature and defects effects on mechanical properties of selected single and bicrystalline...

Understanding the nanoscale mechanical properties of rocks, particularly at higher temperatures, has always been a critical issue for high-temperature rock engineering applications. In this study, two geomaterials, including α-quartz and halite salt, are selected to investigate the effect of temperature, defects, including crack and grain boundaries (GB), on the mechanical properties by employing three-dimensional (3D) Molecular dynamics (MD) simulation. Based on this study, the fracture strength of the pristine sample of crystalline α-quartz and halite salt is 110 GPa and 2 GPa, respectively. In this regard, calculated Young's modulus of crystalline α-quartz and halite salt is 94 GPa and 41 GPa, respectively. According to the results, by adding a crack, the maximum fracture strength of α-quartz and halite salt is dropped 61% and 30%, respectively. However, Young's modulus does not change significantly. Also, it is found that increasing the temperature from 400 K to 800 K in crystalline quartz and halite salt, decreases fracture strength by nearly 35% and 42%, respectively. Moreover, by elevating the temperature from 400 K to 800 K in halite salt, the rocks behavior tends to be more ductile. In terms of the impact of grain boundaries on the mechanical response, the fracture stress of α-quartz is dropped down to 45 GPa, and in halite salt, the fracture stress is reduced to 1.6 GPa.