Influence of the variation in the Hubbard parameter (U) on activation energies of CeO2-catalysed reactions

Accurate description of thermodynamic, structural, and electronic properties for bulk and surfaces of ceria (CeO2) necessitates the inclusion of the Hubbard parameter (U) in the density functional theory (DFT) calculations to precisely account for the strongly correlated 4f electrons. Such treatment is a daunting task when attempting to draw a potential energy surface for CeO2-catalyzed reaction. This is due to the inconsistent change in thermo-kinetics parameters of the reaction in reference to the variation in the U values. As an illustrative example, we investigate herein the discrepancy in activation and reaction energies for steps underlying the partial and full hydrogenation of acetylene over the CeO2(111) surface. Overall, we find that both activation and reaction energies positively correlate with the increase in the U value. In addition to benchmarking against more accurate theoretical methodologies, we suggest that U values are better optimized against kinetics modelling of experimentally observed profiles of products from the catalytic-assisted system of reactions.

First-principles study of phase stability, electronic and mechanical properties of plutonium sub-oxides

Formation energies of PuO2, α-Pu2O3 and sub-oxides PuO2−x (0.0 < x < 0.5) are determined using density functional theory employing generalised gradient approximation corrected with an effective Hubbard parameter.

Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

The structural stability and magnetic properties of a grain boundary (GB) formed by two ZnO single crystals oriented at 45° is investigated by density functional theory, using generalized gradient approximation (GGA) with Hubbard parameter (U).

Phase stability, electronic structures and elastic properties of (U,Np)O2 and (Th,Np)O2 mixed oxides

Mixing enthalpies (ΔHmix) of U1−xNpxO2 and Th1−xNpxO2 solid solutions are derived from atomic scale simulations based on density functional theory (DFT) employing the generalised gradient approximation corrected with an effective Hubbard parameter (Ueff).

Adsorption of Aun (n = 1–4) clusters on Fe3O4(001) B-termination

The adsorption of Aun (n = 1–4) clusters on stoichiometric, reduced and hydrated Fe3O4(001) B-terminations were studied using the GGA density functional theory including the Hubbard parameter (U) to describe the on-site Coulomb interaction.

Density Functional Theory Calculations On Magnetic Properties Of Actinide Compounds

ABSTRACTWe have performed a detailed analysis of the magnetic (collinear and noncollinear) order and atomic and electron structures of UO2, PuO2 and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT+U). We have shown that the 3-k magnetic structure of UO2 is stabilized for the Hubbard parameter value of U=4.6 eV (while J=0.5 eV) when Dudarev’s formalism is used. UO2 keeps cubic shape in this structure. Two O atoms nearest to each U atom in direction of its magnetic moment move toward this U atom. Neither UN nor PuO2 shows the energetical preference for the rhombohedral distortion, in contrast to UO2, and, thus, no complex 3-k magnetic structure in these materials. Both materials have the AFM tetragonal <001> structure at reasonable choice of parameters U and J.

A comparative study on the LDA + U and hybrid functional methods on the description of the electronic structure of YTiO3 under high pressure

The electronic structures of YTiO3 under pressure have been studied with LDA + U (local density approximation + Hubbard parameter) and hybrid functional methods. From matching the experimental band gaps, the Hubbard U and hybrid functional mixing parameters were determined. It is found that both parameters vary with the pressure. Analysis of the electronic structures indicates that the description of the chemical bonding is also dependent on the method of choice.