A new model has been developed for the solute redistribution in single crystals grown by the Axial Heat Processing (AHP) technique by considering the back diffusion in the annular gap between the submerged baffle and the crucible wall. The model has been extended to predict the interface stability based on the constitutional undercooling criterion. The new model (AHP Back-Diffusion) is verified using five Ge-Si crystals grown by the AHP method with different combinations of pulling rates, initial concentrations, and initial melt heights. Predictions of the AHP Back-Diffusion model are superior to the existing models and are in pretty good agreement with the experimental outcomes. (C) 2011 Elsevier B.V. All rights reserved.