Melting line and thermal equation of state of fcc-cobalt: A combined experimental and computational approach

Abstract

The melting line of cobalt has been investigated both experimentally, using synchrotron X-ray diffraction coupled with laser-heated diamond anvil cells, and theoretically, using ab initio simulations. Over the investigated pressure and temperature range – between 30 and 100 GPa and from ambient temperature up to 4000 K – the hexagonal close-packed structure, stable at ambient conditions, is replaced at high temperature by the face-centered cubic structure, observed stable till melting. The melting temperatures obtained by the two methods are in remarkable agreement and the melting line can be well described by a Simon–Glatzel equation of the form Tm= 1768(K)(P(GPa)/35.62+1)0.64. Finally, from the obtained results it was possible to determine a thermal equation of state for the cubic face-centered phase of Co.