Pressure-induced Structures and Structural Evolution in Iron

Molecular-dynamic simulations have been used to study the structure evolution in iron melts rapidly cooled under different pressures. An extreme cooling rate (4x10 super(12) K/s) was adopted in the cooling process. The simulation results show that at the ambient pressure, martensitic transformation happened. However, at a pressure of 1.4GPa, the system passes from bcc structure to a less closed packed structure which is composed of both full icosahedra clusters and bcc structure. With the increase of pressures, an amorphous state was observed, and a compacted local structure with more defected icosahedra is obtained. This work contributes to a better understanding about the dynamics of phase transitions in iron under high pressure, especially during the extremely fast cooling process.