Periodic density functional study of Rh and Pd interaction with the (100)MgO surface

The adsorption geometry and electronic properties of palladium and rhodium atoms deposited on the regular (100)MgO surface were analyzed by means of periodic DFT calculations using local, gradient-corrected and hybrid (B3LYP) functionals. Spin-polarized computations revealed doublet spin state of Rh atom to be the most stable electronic state for the adsorbed rhodium atom on (100)MgO. The preferred adsorption site of the metal (Pd and Rh) atoms was found to be the site on top of the surface oxygen atoms. A relatively stable geometry for the adsorption of the Pd and Rh in a bridge position above the two surface oxygens was found as well. The electronic structures suggested partly covalent bonding with contribution from electrostatic attraction between the metal and the oxygen atoms for both optimized structures. Small charge transfer was obtained from the support to the Pd and Rh metal atoms. The calculations showed that rhodium was bound stronger to the substrate probably due to stronger polarization effects

A DFT study of the NO adsorption on Pdn (n = 1–4) clusters

We report a density-functional study of some properties of the adsorption process of the NO molecule on small palladium clusters (n = 1–4). The interaction between NO and the Pdn clusters is studied on various adsorption sites. Both, NO and Pdn geometrical relaxations are taken into account. The significant conformational reconstruction of the metallic cluster upon NO adsorption induces a large decrease of the NO adsorption energy. Nevertheless, the N–O binding energy is strongly weakened when the molecule is adsorbed on the small Pdn clusters due essentially to an electrostatic repulsion between both N and O atoms. The possible dissociation process of NO on Pd4 cluster is then investigated within two processes: the NO molecule does not dissociate on Pd4 with process (i) (dissociation of the isolated gas phase NO molecule followed by the adsorption of both nitrogen and oxygen atoms on the cluster). Process (ii)which presents three successive steps (adsorption of the NO molecule, dissociation of the NO molecule adsorbed on Pd4, adsorption of the O atom on the cluster) is studied in details and we propose a reaction pathway locating transition states and intermediate species. The activation energy for process (ii) is high and the dissociation of the NO molecule on the Pd4 cluster is thus highly improbable

DFT Simulation of XPS Reveals Cu/Epoxy Polymer Interfacial Bonding

Experiments and computations are performed to assess the interfacial bonding between Cu and a poly-epoxy surface relevant to many applications. The surface of the poly-epoxy is characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy before and after ultrahigh vacuum Cu deposition. Modifications of the XPS spectra are observed, suggesting a strong interaction between specific C and O atoms of the surface with Cu. Density functional theory (DFT) calculations are then performed to simulate XPS spectra and to better understand bonding. DFT computations are performed in the framework of the uGTS methodology, which takes initial and final state effects into account, and allows to calculate chemical shifts between the different C 1s and O 1s molecular orbitals with good accuracy, for the pristine surface. DFT calculations are then set to determine the preferential adsorption sites of Cu on different sites of the polymer surface. Finally, XPS simulation of the C 1s and O 1s spectra with Cu adsorbed at these sites matches very well with the experimental spectra, indicating that Cu atoms interact preferentially with hydroxyls to form Cu−O−C bonds, stabilized by a transfer of 0.5 electrons from Cu to O; hence, Cu is partially oxidized

Selectivity study from the density functional local reactivity indices

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Third order energy derivative corrections to the Kohn-Sham orbital hardness tensor

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Orbital hardness tensors from Hydrogen through Xenon from Kohn-Sham perturbed orbitals

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Atomic Fukui indices and orbital hardnesses of adenine, thymine, uracil, guanine and cytosine from density functional computations

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Application of vibrational correlation formalism to internal conversion rate: Casestudy of Cu n (n = 3, 6, and 9) and H2/Cu3

International audienceThis work reports non-radiative internal conversion (IC) rate constants obtained for Cun with n = 3, 6,and 9 andH2 onCu3. TheTime-Dependent Density Functional Theory (TDDFT) methodwas employedwith three different functionals in order to investigate the electronic structures and the absorptionspectra. The performance of the generalized gradient approximation of Perdew, Burke and Ernzerhof(PBE) and the hybrid B3LYP and PBE0 exchange correlation functionals in combination with the SVPand the def2-TZVP basis setswas examined.TDDFTresults were used as input data to compute internalconversion rate constants. For this purpose, we have developed a program package. A descriptionof the theoretical background used in our numerical implementation and the program input file ispresented. In viewof future applications of this program package in photoinduced catalysis, we presentthe analysis of the IC rate processes for the photodissociation of H2 on Cu3. These results showedthe applicability of the method and the computational program to identify the vibrational modes intransition metal clusters giving rise to the largest IC rate constant due to their interactions with theexcited electronic states occurring in the hot-electron induced dissociation phenomena

Structural properties of Y-doped BaZrO3 as a function of dopant concentration and position: A density functional study

International audienceRelative stabilities, structural details and hydrogen binding sites in models of Y-doped barium zirconates with 12.5, 25 and 37.5% yttrium have been studied using Density Functional Theory (DFT) based periodic approach. Two stable crystal structures were obtained for the possible Zr substitutions in the 25 and 37.5% Y-containing BaZrO3. Tetragonal space group symmetries were found for Y≥25% and a volume reduction is obtained with increasing the acceptor dopant percentage. Structural and electronic properties remain very similar in all the considered models. A well established charge difference is noticed only for oxygen sites in the three possible Zr\O\Zr, Zr\O\Y and Y\O\Y configurations. Examination of H binding strength in various OH local environments indicated a general tendency to stabilize the O\H bonds in the Zr\OH\Y configuration(s) compared to the Zr\OH\Zr ones. A clear tendency of increasing the O\H stabilization with increasing Y content from 12.5 to 25% is not obtained. The strongest O\H bonds are formed in the 37.5% Y-doped BaZrO3 model. Formation of O\H bonds in Y\OH\Y configurations was not found that suggest a smaller probability for H-uptake in Y-doped zirconates with high Y\O\Y concentrations