Dynamical stability of iron under high-temperature and high-pressure conditions

The dynamical stability of iron under high-temperature and high-pressure conditions was investigated based on the phonons evaluated by using a recently developed method. It is revealed that both the fcc-Fe and the hcp-Fe are dynamically stable in a wide temperature and pressure range. The bcc-Fe phase can be stable as well, while in a limited temperature/pressure regime bounded by a dynamical stability limit and a harmonic limit. Direct evidence shows that it is the entropy term that plays a critical role in stabilizing the bcc-Fe under high-temperature and high-pressure conditions.