Molecular Dynamics Analyses of Crack Growth Behaviors in Single Crystalline Fe by the Use of Hybrid Potential Method

In Molecular Dynamics (MD) simulations, interatomic potentials have significant effects on the results and calculation time, i.e. analysis sizes. In this paper, first, the crack growth behaviors in α-Fe calculated by three representative interatomic potentials, the Embedded Atom Method (EAM) potential fitted by Simonelli, G. et al., Finnis-Sinclair (FS) potential and Second Nearest-neighbor Modified EAM (MEAM) potential, are compared, and the reliability of the results obtained by the MEAM potential is confirmed based on the reproducibility of the important physical properties. Although the MEAM potential is reliable, we show that the computational time required by the MEAM potential is more than 50 times of the FS potential. Here, we propose “Hybrid Potential Method” which selectively uses different interatomic potentials according to the local atomic structure, and connects those potentials by the use of handshake method. We use FS potential, which is efficient in calculation, for bcc structure and the MEAM potential, which is accurate but time consuming, for non-bcc structures. The availability of the Hybrid Potential Method is demonstrated, and then the method is applied to crack growth simulations using large calculation models. We report the phase transformations and grain nucleation near the crack tip during crack growth.