Near-surface controls on the composition of growing crystals: Car-Parrinello molecular dynamics (CPMD) simulations of Ti energetics and diffusion in alpha quartz

Although our results are strictly applicable only to Ti in α quartz, the demonstration that impurity atom energetics and diffusion are functions of depth in the near-surface region may be broadly applicable, given the similarity in measured length scale of the near-surface relaxed region in a wide variety of minerals. Kinetic models of impurity uptake that do not consider these factors may be incomplete.