Exploration of the Phase Space of the Morse Potential

Abstract

Knowledge of phase stability is important due to its usage in a variety of areas ranging from drug formulation to semiconductor production. The most common method of understanding phase stability is through a phase diagram, however extensive phase diagrams can be hard to determine experimentally. As such, theoretical models have seen significant use in computing phase diagrams. The Morse potential has previously been used to describe diatomic molecules and metals, but to the best of our knowledge, the phase space of the Morse potential has never been comprehensively studied. In this work, the phase space of the Morse potential with a range of parameters most applicable to simulating metals is studied. Particular emphasis is placed on the solid and liquid phases, due to previous studies on the vapor-liquid equilibrium of the Morse potential. Thermodynamic integration is used to calculate the chemical potential of different phases and these are compared to generate temperature-pressure phase diagrams spanning the phase space of interest. Particular interest is paid to the propagation of error, to the fitting of thermodynamic functions for thermodynamic integration, and to the fitting of chemical potential surfaces.