Stepwise-equilibrium and Adaptive Molecular Dynamics Simulation for Fracture Toughness of Single Crystals

A stepwise-equilibrium and adaptive molecular dynamics (MD) simulation scheme for investigating the fracture toughness of single crystals is proposed in this study. The critical fracture toughness is found by conducting MD simulations along with the gradually increasing external load. At each load step, an equilibrium state is obtained by relaxing the system from the initial state generated. This is done by adjusting the atomic position using an additional displacement of linear elastic solution corresponding to the current load increment. The load increment is adjusted at each step in an adaptive way in order to achieve high computational efficiency and accuracy. A nickel crystal having 14256 atoms is investigated using this technique. The critical stress intensity factor in the (1[UNKNOWN]0) plane is found to be 0.7436 MPa √m, while the fracture stress is 4.7776 GPa. The effects of vacancies on the critical stress intensity factors are also investigated.