  From the Ising model and the Lennard-Jones fluid, to water and the
iron-carbon system, phase diagrams are an indispensable tool to understand
phase equilibria. In spite of the effort of the simulation community the
calculation of a large portion of a phase diagram using computer simulation is
still today a significant challenge. Here we propose a method to calculate
phase diagrams involving liquid and solid phases by the reversible
transformation of the liquid and the solid. To this end we introduce an order
parameter that breaks the rotational symmetry and we leverage our recently
introduced method to sample the multithermal-multibaric ensemble. In this way
in a single molecular dynamics simulation we are able to compute the
liquid-solid coexistence line for entire regions of the temperature and
pressure phase diagram. We apply our approach to the bcc-liquid phase diagram
of sodium and the fcc-bcc-liquid phase diagram of aluminum.
