Anharmonicity in a linear chain of Lennard-Jones atoms

Atoms in solids move in the force fields of their vibrating neighbors and these vibrations give rise to thermodynamics. In many systems it is enough to use the Taylor expansion of the potential energy up to second order to derive most of their thermodynamic properties, but higher order (anharmonic) terms are necessary to predict quantities that depend on scattering rates, such as thermal conductivity. Here we present a study of the anharmonicity that arises from atoms in a linear chain interacting via the Lennard-Jones potential and a test run of a dynamic mean field theory in which the atoms only see a harmonic potential but the stiffness of the potentials depends on the configuration of the system which is determined using a machine learning classifier.