71 research outputs found
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Mechanisms of ammonia and hydrazine synthesis on η-Mn3N2-(100) surfaces
Understanding the mechanism of catalytic reactions is crucial for the future development of catalysts. In this computational study, dispersion-corrected Density Functional Theory (DFT) theory was used to calculate the various mechanistic pathways for ammonia and hydrazine synthesis on η-Mn3N2-(100) surfaces. A simple Lewis structure representation algorithm was used in order to locate various possible NxHy intermediates. Hydrogenation of dinitrogen results in significant activation of the inert triple bond and these intermediates have a significant role in the ammonia and hydrazine synthesis reaction on manganese nitrides via a Langmuir-Hinschelwood mechanism. It is anticipated that these findings are significant in developing new catalysts for hydrazine synthesis using η-Mn3N2 (100) catalysts
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Linear correlation of vertical ionization energies and partial charges on acetaldehyde and methyl formate radicals in various solvents
We have studied the vertical ionisation energy (IE) and the partial charge on the carbonyl carbon atom of acetaldehyde and methyl formate radicals, in various solvents (i.e. cyclohexane, benzene, methanol, ethanol, DMSO, water, acetonitrile, THF, chloroform). We find a linear correlation between the IE and the partial charge on the carbonyle carbon of these radicals. This suggests that there is a small solvent effect on the rate of radical to carbocation formation for radicals such as acetaldehyde and methyl formate radicals, which can be explained on a simplified point charge model following Coulomb's law
Computational Inhibition Studies of the Human Proteasome by Argyrin-Based Analogues with Subunit Specificity
Study of the cap structure of (3,3), (4,4) and (5,5)-SWCNTs: Application of the sphere-in-contact model
Quantitative Structure-Property Relationships for Longitudinal, Transverse, and Molecular Static Polarizabilities in Polyynes
Kinetic Rates and Linear Free Energy Relationships for Water Dissociation on Transition and Noble Metal Dimers
DFT-D3 study of H 2 and N 2 chemisorption over cobalt promoted Ta 3 N 5-(100), (010) and (001) surfaces
The reactants for ammonia synthesis have been studied, employing density functional theory (DFT), with respect to their adsorption on tantalum nitride surfaces. The adsorption of nitrogen was found to be mostly molecular and non-activated with side-on, end-on and tilt configurations. At bridging nitrogen sites (Ta–N–Ta) it results in an azide functional group formation with a formation energy of 205 kJ mol−1. H2 was found also to chemisorb molecularly with an adsorption energy in the range −81 to −91 kJ mol−1. At bridging nitrogen sites it adsorbs dissociatively forming >NH groups with an exothermic formation energy of −175 kJ mol−1 per H2. The nitrogen vacancy formation energies were relatively high compared to other metal nitrides found to be 2.89 eV, 2.32 eV and 1.95 eV for plain, surface co-adsorbed cobalt and sub-surface co-adsorbed cobalt Ta3N5-(010). Co-adsorption of cobalt was found to occur mostly at nitrogen rich sites of the surface with an adsorption energy that ranged between −200 to −400 kJ mol−1. The co-adsorption of cobalt was found to enhance the dissociation of molecular hydrogen on the surface of Ta3N5. The studies offer significant new insight with respect to the chemistry of N2 and H2 with tantalum nitride surfaces in the presence of cobalt promoters
Size-dependent bond dissociation enthalpies in single-walled carbon nanotubes
We report the bond dissociation enthalpy (BDE) and the local electronic properties of Single-Walled Carbon Nanotubes (SWCNT) using density functional theory. Our analysis shows that there is a strong size-dependence of the BDE of these SWCNTs, which is inversely proportional to the radius-squared (1/r2) and the length (1/l) of SWCNT. We derive quantitative relationships from which the BDE can be calculated as a function of size and radius of the SWCNT. We find that the BDE of SWCNT outside the size-dependent region is about 480 kJ mol−1, which can be used for thermochemical calculations
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