Simulating the Distillation of Fe Impurities in O-Ne White Dwarfs

White dwarfs are remnants of low mass stars, primarily made of elements like carbon, oxygen, and neon. Unlike our sun, white dwarfs do not have fusing cores or a heat source, so they cool monotonically, and the ionized plasma mixtures separate and crystallize in their cores. In this work, we study the behavior of trace iron nuclei O-Ne-Fe mixtures using molecular dynamic simulations and quantify the phase of matter using the bond order parameter. We simulate small Fe nanocrystals in O-Ne liquids to study the coexistence of highly concentrated Fe solids in these mixtures, with implications for Fe distillation. In simulations of large volumes of solid Fe and O-Ne liquids, we find a a complex interface structure which is evidence of surface whetting in strongly coupled plasmas. Meanwhile, simulations of O/Ne solids in coexistence with O-Ne-Fe liquids find that Fe is excluded from O-Ne lattices. We observe O-Ne mixtures easily form a bcc lattice, whereas the iron nuclei, due to its much larger charge, is excluded from this structure and forced into pockets of remaining disorder, providing direct evidence that Fe can distill in O/Ne/Fe cores.