ALADYN, a set of codes to compute lattice dynamical properties of anharmonic crystalline materials: phonons, thermal conductivity and state of equilibrium at high temperatures

We introduce a set of codes we have developed over more than a decade ago to compute lattice dynamical properties of crystalline solids based on first-principles data. They include FOrce Constants EXtraction (FOCEX), which can extract from force-displacements in one or many supercells the harmonic and anharmonic force constants up to potentially order 8. The order and the range of force constants are set by the user and correspondingly, appropriate set of force-displacement data need to be provided. This first-principles data is however much smaller than the ones needed for machine learning potentials. The THERMACOND code, can calculate the exact solution to the steady-state phonon Boltzmann equation and the corresponding thermal conductivty. Finally, the state of thermal equilibrium, i.e. lattice shape, equilibrium atomic positions and effective force constants are computed from a free energy minimization using the code SCOP8, which is based on the self-consistent phonon approximation. Examples will be presented to illustrate the capabilities of these codes.