Structures and equation of state of ∈-Fe under high pressure

The equation of state (EOS) and the axial ratio c/a of ∈-Fe at high pressures are investigated by using the generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory (DFT). The results show that at the lower pressure, the EOS of ferromagnetic ∈-Fe is consistent with the experimental result. While at higher pressure, the EOS of the nonmagnetic ∈-Fe is in good agreement with the experimental result. Meanwhile, we find an obvious increase of the axial ratio c/a with pressure, and there is only a small increase with increasing temperature at high pressure.