Pratik Dholabhai

A density functional study of atomic oxygen and carbon adsorptions on (100) surface of γ-Uranium

Oxygen and carbon adsorptions on a ?-Uranium (U) (100) surface have been studied at both non-spin-polarized (NSP) and spin-polarized (SP) levels using the generalized gradient approximation of the density functional theory (GGA-DFT) with Perdew and Wang (PW) functionals. For oxygen adsorption, the bridge position of (100) surface is found to be the most favourable site with chemisorption energy (CE) of 7.887?eV for the NSP case, and 7.965?eV for the SP case. The distances of the oxygen adatom from the U surface are found to be 1.19? and 1.22?? for the NSP and SP cases, respectively. The magnetic moment for this most favourable site is found to be 0.167?B per atom. For carbon adsorption, the centre position of (100) surface is found to be most favourable site with CE of 7.816?eV for the NSP case, and 7.895?eV for the SP case. The distances of the carbon adatom from the U surface are found to be 0.62 and 0.52?? for the NSP and SP cases, respectively. The magnetic moment for this most favourable site is found to be 0.084?B per atom. The hybridization between the O 2p orbitals and U 5f orbitals is found to be rather weak but the hybridization between the C 2p orbitals and U 5f orbitals is observed to be strong.

AN AB INITIO STUDY OF CHARGE STATE EFFECTS ON THE USE OF

The formalism of density functional theory (DFT) with Perdew and Wang exchange-correlation functional, has been employed to study the electronic and geometric structures of silver cation and the neutral dimer bonded with carbon monoxide and oxygen. A charge state study of the use of and Ag2, for the catalytic oxidation of CO, has been performed and compared with our previous results for . Different possible structures for , Ag2CO+, Ag2O2 and Ag2CO have been investigated in detail. An all electron 6-311 ++ G** basis set for carbon and oxygen, and a pseudopotential basis set for silver have been used for performing the calculations. Using silver cation and neutral dimer as catalysts, full catalytic cycles producing two carbon dioxide molecules have been presented. Also, the presence of intermediate states, and Ag2CO3, which can be detected experimentally, are predicted. The presence of an energy barrier for certain reactions from the catalytic cycle have been observed. This is noteworthy since no reaction barrier has been observed using silver anion dimer as a catalyst, for the same catalytic cycle. Analyzing the charge state effects, it is concluded that silver anion dimer performs better as a catalyst, compared with silver cation and neutral dimers.