We present a kinetic lattice Monte Carlo study of the behavior of a dopant
flux driven by a vacancy gradient, associated with the diffusion of substit
utional impurities via a vacancy mechanism in silicon. Recent ab initio res
ults are used for a quantitative description of the impurity-vacancy intera
ction. We find a dopant flux smaller than, but in the same direction as, th
at predicted by the pair diffusion model, with the deviation greatest at hi
gh temperatures.