Search

Using density functional theory, two mechanisms of covalent bonding of dapsone onto functionalised carbon nanotubes have been investigated, the first one being direct bonding and the second one being bonding by using coupling agents. In this work, the mechanism of functioning of an important coupling agent (1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b]pyridinium 3-oxide hexafluorophosphate, N-HATU) has been investigated. The activation energy and activation Gibbs free energy of the two pathways have been calculated and compared with each other. It was found that using the coupling agents will reduce the energy barrier. All of the calculations have been performed in the solution phase (polarised continuum model) using the B3YLP hybrid density functional.

Using density functional theory, the mechanism of adsorption of 2-chlorophenol from water in the presence of γ-Fe2O3nanoparticles was investigated. Fe2O3nanoparticles were modelled using Fe6(OH)18(H2O)6ring clusters. 2-chlorophenol can coordinate to the γ-Fe2O3nanoparticles via its own OH or Cl groups. The process produces two intermediates which will be converted into final products through two pathways (Cl pathway and OH pathway). The activation energy and activation Gibbs free energy of the two pathways have been calculated and compared with each other. It was found that the OH pathway is under thermodynamic control and the C1 pathway is under kinetic control. All of the calculations were performed using a hybrid density functional method (B3LYP) in the solution phase (PCM model).

In this work, using quantum mechanics, the mechanism of reaction between 2-aminopyrimidine with dichloro-[1-methyl-2-(naphthylazo) imidazole] palladium(II) complex was investigated. The reaction produces two five-coordinated intermediates which are converted into final products through two possible pathways (nucleophile-dependent pathway and solvent-dependent pathway). The activation energy and activation Gibbs free energy of two pathways have been calculated and compared with each other and experimental results. These activation energies for the solvent-dependent pathway are greater in comparison with the nucleophile-dependent pathway which demonstrates that the latter is the dominating route and makes the main contribution to the reaction. Considering solvent effects, the activation Gibbs free energy for the rate determining step of the nucleophile-dependent pathway was calculated, which was in good agreement with the experimental value. Although the theoretical activation energy shows a suitable behaviour qualitatively, it is not fully consistent with the experimental value. All of the calculations were performed using a hybrid density functional method (B3LYP) in the solution phase (PCM model).

Friction factors for fully developed flow in triangular ducts with fins of various height and width are investigated for Reynolds numbers ranging from 150 to 90,000. Two triangular ducts having apex angles of 60 and 38.8 deg are studied. Results are presented in the form of standard plots of friction factor as a function of Reynolds number. Friction factor values for the smooth triangular duct cases are in good agreement with the existing results. For the finned-duct cases, the fully developed axial velocity profiles in laminar flow are determined by solving the x-momentum equation iteratively by the Gauss–Seidel finite-difference technique. The theoretically determined friction factors for these cases are in good agreement with the experimental values of friction factors based on pressure drop measurements.