Calculation of phase diagrams in the multithermal-multibaric ensemble

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. Despite 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. This repository contains the input files to reproduce the results of the paper mentioned above. The results are divided into two zip files Al.zip and Na.zip for simulations of aluminum and sodium, respectively. Inside each folder there is an example for the calculation of free energies at constant temperature and pressure, and the input files and results of the multithermal-multibaric simulations.