Further study of the quantum dot potential for Si is presented. This potential has been calculated by means of our recent empirical model. The indirect energy gap (Gamma-X) is calculated using the full potential-linearized augmented plane wave (FP-LAPW) method. The Engel-Vosko generalized gradient approximation (EV-GGA) formalism is used to optimize the corresponding potential for energetic transition and optical properties calculations of Si. The refractive index and transverse effective charge are predicted as a function of dot diameter that is in turn used to test the validity of our model. The obtained results show a reasonable agreement in comparison with experimental data and theoretical results. (C) 2011 Elsevier Ltd. All rights reserved.