For energy band calculations, the indirect energy gap (Gamma - X) is calculated using density functional theory (OFF) of the full potential-linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2K code. The Engel-Vosko generalized gradient approximation (EV-GGA) formalism is used to optimize the corresponding potential for energetic transition and optical properties calculations of CdS and CdTe as a function of quantum dot diameter and is used to test the validity of our model of quantum dot potential. The results are compared with others and showed reasonable agreement. (C) 2012 Elsevier Ltd. All rights reserved.