DHCP AS A POSSIBLE NEW EPSILON' PHASE OF IRON AT HIGH-PRESSURES AND TEMPERATURES

Using in-situ X-ray diffraction and ab initio theoretical calculations , we have identified a possible new phase of iron, epsilon'-Fe, in the stability field of what was previously known for epsilon(hcp)- and ga mma(fcc)-Fe, The crystal structure of epsilon'-Fe is indexed to a dhcp structure with an ABAC stacking sequence. The epsilon'-phase exists a t temperatures lower than the gamma-phase and at pressures between 15 and 40 GPa, which differs from the stability field previously suggeste d for beta-Fe above 40 GPa.