Abstract
Density functional theory (DFT) calculations are performed to study the conformations, hydrogen-bonding network, and the stabilities of all possible molecular associations, urea-(H2O)(n), (n = 1-5) in aqueous solutions of urea. The B3LYP functional and the basis set 6-311++G(d, p) are used through the calculations. Natural bond orbital (NBO) theory and atoms in molecule (AIM) analysis are applied to quantify the relative strength of hydrogen bond interactions and to account their effect on the stabilities of molecular arrangements. The charge transferred from lone pair of the hydrogen bond acceptor to antibonding orbital of the donor provides the substantial stabilizing component of the hydrogen bond. The energy analyses prove that O-H...O interactions between water molecules give more stability of the clusters. The hydrogen bonded structure is found to be slightly influenced by the presence of urea molecules. (C) 2015 Elsevier B.V. All rights reserved.