Structural Phase Transition of Single-Crystalline Iron under Shock Loading along the [110] Direction: Molecular Dynamics Simulations Based on Different Potential Functions

Single-crystal iron is a prototypical system for studying the dynamic behavior of metallic materials under shock loading, which is of great significance in high-pressure phase transition research due to its phase transformation mechanisms and mechanical response characteristics. In this work, molecular dynamics simulations were performed to investigate the mechanical response of single-crystal iron under shock loading along the [110] crystallographic direction. Three different potential functions (Ackland, Mishin, optimized MAEAM) were employed to examine differences in stress transmission, dislocation activity, and new phase formation, as well as to explore the coupling mechanisms between plasticity and phase transformation. The research results show that the body-centered cubic-hexagonalclose-packed (BCC-HCP) phase transition pressure (14.03 GPa) predicted by the Ackland potential function is closest to the experimental data and can better describe the coupling of plastic deformation and phase transition; the Mishin potential function shows an independent plastic stage at high strain rates; the optimized MAEAM potential function gives a higher BCC-FCC (face-centered cubic) phase transition pressure threshold (49.91 GPa), which is more consistent with the phenomenon that the FCC phase was not observed in the experiment. In addition, the three potential functions all show the same phase transition mechanism: from BCC compression to shear-induced stacking fault formation and its reorientation.