Molecular dynamics study of melting curve, entropy of fusion and solid–liquid interfacial energy of cobalt under pressure

We performed molecular dynamics (MD) simulations with the two embedded atom method (EAM) potentials to calculate the melting curves of cobalt over a wide range of pressure. Zhou׳s EAM potential can produce satisfying results, in better agreement with the experiment compared with Pun׳s. Based on Zhou׳s potential, we simulated the melting of Co with two approaches, i.e., the one-phase (hysteresis) method and two-phase (solid–liquid coexistence) method. Both approaches can effectively reduce the superheating, and their results are in the close proximity at the applied pressures. With the one-phase method, during the investigation of the entropy of fusion of Co, we found that with the pressure increasing, the entropy of fusion decreases rapidly first and then oscillates with pressure; when the pressure is beyond 100 GPa, the entropy of fusion shows less pressure effect. When taking account of the solid–liquid interfacial energy at different pressures, we found that it increases monotonically with pressure, and can be well described as a fifth-order polynomial relation. Moreover, the thermal equation of state (EOS) and the temperature dependence of atomic structures of Co have been obtained successfully.