The function of nanometer-size quantum dots (QDs) of ternary compound semiconductors, such as InxGa1-xAs and ZnSe1-xTex, used in the fabrication of optoelectronic and photovoltaic devices can be optimized by precise tuning of their electronic band gap through control of the QD composition (x) and diameter. Results on compositional distributions in ternary QDs and how they affect the QDs' electronic band gap are reported. A hierarchical modeling approach is followed that combines first-principles density functional theory calculations and classical Monte Carlo simulations with a continuum model of species transport in spherical nanocrystals. In certain cases, the model predicts the formation of core/shell-like structures with shell regions rich in the surface segregating species. A systematic parametric analysis generates a database of transport properties, which can be used to design post-growth thermal annealing processes that enable the development of thermodynamically stable QDs with optimal electronic properties grown through simple one-step colloidal synthesis techniques. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3223-3236, 2013