We determined the nonlinear optical properties of two organic crystals 2-(4-chlorophenyl)-N-(2-iodophe nyl)acetamide and 2-(4-chlorophenyl)-N-(pyrazin-2-yl)acetamide, to understand their linear and nonlinear optical behavior in the static and dynamic cases. A new approach treating the supermolecule is employed in combination with an interactive electrostatic system in which the atoms of neighboring molecules are considered as point charges. The ab initio computational results of (hyper) polarizabilities are derived from an iterative process and confirm these crystals as good candidates for photonic devices, such as optical switches, modulators, pyrazoline derivatives and optical energy applications. (C) 2017 Elsevier B.V. All rights reserved.