The LAMMPS package as a tool for teaching phase transition

The interpretation and description of natural phenomena, intrinsic to Science, require conceptual abstraction, using observations and theoretical constructs. Concepts like atoms and molecules, along with mathematical equations, have been developed to describe interactions and the temporal evolution of natural properties. Careful analysis of these models, considering thermodynamic parameters, enables the investigation of complex phenomena. Computational tools, such as Molecular Dynamics, allow for the modeling of atomic-molecular systems, aiding in the understanding of matter transformations. The Lennard-Jones potential, an isotropic model proposed in the 1920s, is effective in the thermodynamic description of simple fluids. In this work, we will review this model to construct the temperature and density phase diagram ($T\times \rho$) using Molecular Dynamics simulations with LAMMPS, available freely online. We will obtain critical temperature and density, as well as the coexistence region of the liquid and vapor phases. This will provide physics teachers at all educational levels with a simple computational approach to teach about phase transitions.

Keywords:
Thermodynamics; Phase Diagrams; Molecular Dynamics; Lennard-Jones