Pressure Dependence of Pure Zirconium Liquid–Solid Phase Transition

Molecular dynamics simulations were conducted at a cooling rate of 1.0 × 1011 K/s to investigate the solidification mechanism of zirconium (Zr) under high pressure. Three distinct pressure-dependent regimes are identified: crystallization into a body-centered cubic (BCC) phase below 27.5 GPa, vitrification between 27.5 and 65 GPa, and crystallization into an A15 phase above 65 GPa. The volume change during crystallization is found to reverse at critical pressures of 5 and 103 GPa, and anomalous behavior is observed at the phase boundaries: at 27.5 and 65 GPa, the volume varies continuously despite a sharp drop in potential energy, whereas at 65 GPa, the volume decreases abruptly while the energy changes smoothly. Structural analysis indicates that evolution in the low-pressure regime is governed by atomic configurations extending to the second-neighbor shell, while at high pressures, nearest-neighbor interactions become dominant. This work clarifies the microstructure–pressure relationship during metallic solidification, providing insights into controlling phase transitions under extreme conditions.