Isolating Diffusion Coefficients of Lattice Defects in Coulomb Crystals

The diffusion coefficients of Coulomb crystals, as applicable to stellar astrophysics, have seldom been studied to a satisfactory level. Molecular dynamics (MD) studies such as this inform our understanding of the macroscopic properties of stellar remnants, such as white dwarfs and neutron stars. We use the MD code LAMMPS to simulate small Coulomb crystal lattices of varying temperature and screening length, then introduce defects by either inserting (interstitials) or removing (vacancies) particles. By tracking the propagation of these defects and their interactions with the surrounding lattice, we determine their diffusion coefficients. This research enhances current understandings of defect-driven diffusion in strongly coupled plasmas, thereby influencing knowledge of the thermal and mechanical evolution of the dense matter within white dwarfs and neutron star crusts.