Diffusion of neon in white dwarf stars

Sedimentation of the neutron rich isotope N 22 e may be an important source of gravitational energy during the cooling of white dwarf stars. This depends on the diffusion constant for N 22 e in strongly coupled plasma mixtures. We calculate self-diffusion constants D_i from molecular dynamics simulations of carbon, oxygen, and neon mixtures. We find that D_i in a mixture does not differ greatly from earlier one component plasma results. For strong coupling (coulomb parameter Γ> few), D_i has a modest dependence on the charge Z_i of the ion species, D_i Zi -2/3. However, D_i depends more strongly on Z_i for weak coupling (smaller Γ). We conclude that the self-diffusion constant D _Ne for N 22 e in carbon, oxygen, and neon plasma mixtures is accurately known so that uncertainties in D_Ne should be unimportant for simulations of white dwarf cooling.