Interatomic potentials and the simulation of fracture: C15 NbCr2

The discrete nature of solids and the interatomic interactions strongly influence crack propagation. Lattice trapping results in stable cracks above and below the critical Griffith load. Local atomic arrangements near the crack front define fracture behaviour. The analysis of these processes on an atomic scale helps to understand principle mechanisms and their consequences, which also have to be incorporated in more coarse-grained descriptions to get reliable results. Large-scale molecular dynamics simulations of fracture on the atomic level can supply information not accessible to experiment. But to simulate a specific material reasonable effective interatomic potentials are needed. In this paper, we report on the fitting and validation of potentials specifically generated for the fracture of C15 NbCr2. Results are compared to those derived with potentials for the elements from the literature. The comparison indicates that interactions fitted to elemental metals are not sufficient to determine alloy properties.