First-order phase transitions by first-principles free-energy calculations: The melting of Al

The melting properties of aluminum are calculated from first-principles molecular-dynamics simulations using density-functional theory in the local-density approximation. We calculate a melting temperature of 890 K at zero pressure, to be compared to the experimental value of 933 K. An elaborate discussion of the techniques employed is presented. The solid- and liquid-state free energies are obtained via coupling constant integration. The respective reference systems are the quasiharmonic crystal and the Lennard-Jones fluid. Good quality of the Brillouin zone sampling is shown to be crucial. The strategy followed is expected to be applicable to a wide range of liquid metals.