Computational Study of Urea and Its Homologue Glycinamide:  Conformations, Rotational Barriers, and Relative Interactions with Sodium Chloride

Abstract

Conformational behaviors of urea and glycinamide have been investigated using the B3LYP functional with the 6-311+G* and 6-311+G** basis sets. Urea monomers have nonplanar minima at all the levels studied, even in the aqueous phase. In the case of glycinamide, the intramolecular hydrogen bond formed from the amide to the amine is important for stabilizing the global minimum. Bond rotations and nitrogen inversion barriers for glycinamide conformations have also been reported. The DFT calculated results suggest that urea conformers interact preferentially with the {111} surface of sodium chloride and such interactions can be responsible for the change in the habit of sodium chloride. Glycinamide conformers have a lower affinity toward the {111} surface of sodium chloride in water. The pyramidality of nitrogens in urea conformers does not influence the relative trends of interaction energies with sodium chloride surfaces. The mode of interactions predicted at the LDA/PWC/DND level for urea and glycinamide with sodium chloride for both slab and cluster models shows that the amide functionality (-CONH2) interacts with both Na(+) and Cl(-) ions on the {100} surface; however, the carbonyl oxygen of these additives predominantly interacts with the sodium ions on the {111} surface.

First principle study towards the influence of Cd2+ on the morphology of sodium chloride

“…1). We have observed that the relaxation of slab layers does not affect the interaction of organic additives with surfaces [56][57][58], however, it is important to examine the effect of relaxations of slabs with inorganic ions like Cd 2+ . Relaxing the top layer of {1 0 0} and {1 1 1} surface of NaCl with Cd 2+ predicted the similar trend as observed with the fixed surfaces (Supporting information, Fig.…”

“…Therefore, DFT calculated results also revealed that the kink site is more energetically favored than that of flat and step surfaces towards the growth of specific planes compared to steps or ledge sites [2,12]. The magnitude of interaction calculated in the case of Cd 2+ ion is much higher than the organic additives on such surfaces [57][58][59][60]. The calculations performed in water employing the continuum model (COSMO) however, showed reasonably Table 1 Interaction energies calculated at GGA/VWN-BP/DNP for gas phase and GGA/VWN-BP/DNP for aqueous phase (COSMO) level using LDA/PWC/DND optimized geometries for Cd 2+ ion with {1 0 0} and {1 1 1} flat, step and kink sites of NaCl surfaces in kcal/mol.…”

Probing the influence of pH dependent citric acid towards the morphology of rock salt: a computational study

“…[35][36][37][38][39] Three-dimensional (3D) slabs of sodium chloride [{100} and {111}] were generated employing periodic boundary conditions. 6,7 The optimization of additive on the surface was performed with LDA/PWC/DND level of theory and the interaction energies were reported with GGA/PW91/DND level. The conductor-like screening model (COSMO) was employed to take into account the solvent (water) in our calculations.…”

“…The compositions at this pH value are a 0 ¼ 0.02659, a 1 ¼ 0.62638, a 2 ¼ 0.34263, a 3 ¼ 4.4 Â 10 À4 . [6][7][8][9] 3.4 Molecular electrostatic potential (MESP) analysis of citric acid and its dissociated forms…”

“…One of our ongoing efforts to rationalize the morphology of alkali halides in presence of impurities incited to examine the role of pH on citric acid and its influence towards the morphology of sodium chloride crystals. [6][7][8][9]…”