Adsorption and Oxidation of CO on Ceria Nanoparticles Exposing Single-Atom Pd and Ag: A DFT Modelling.

Various CO species formed upon the adsorption and oxidation of CO on palladium and silver single atoms supported on a model ceria nanoparticle (NP) have been studied using density functional calculations. For both metals M, the ceria-supported MCO moieties are found to be stabilised in the order MCO < MCO < MCO, similar to the trend for CO species adsorbed on M-free ceria NP. Nevertheless, the characteristics of the palladium and silver intermediates are different.

Reverse hydrogen spillover on and hydrogenation of supported metal clusters: insights from computational model studies.

"Reverse" spillover of hydrogen from hydroxyl groups of the support onto supported transition metal clusters, forming multiply hydrogenated metal species, is an essential aspect of various catalytic systems which comprise small, highly active transition metal particles on a support with a high surface area. We review and analyze the results of our computational model studies related to reverse hydrogen spillover, interpreting available structural and spectral data for the supported species and examining the relationship between metal-support and metal-hydrogen interactions. On the examples of small clusters of late transition metals, adsorbed in zeolite cavities, we showed with computational model studies that reverse spillover of hydrogen is energetically favorable for late transition metals, except for Au.

First Hybrid Embedding Scheme for Polar Covalent Materials Using an Extended Border Region To Minimize Boundary Effects on the Quantum Region.

We present an improved scheme for constructing the border region within a hybrid quantum mechanics/molecular mechanics (QM/MM) embedded cluster approach for zeolites and covalent oxides that ensures proper modeling of adsorption complexes with QM regions of moderate size. The procedure employs a flexible orbital basis set on monovalent oxygen pseudoatoms at the boundary of the QM cluster and introduces a pseudopotential description without explicit representation of valence electrons for their immediate Si neighbors in the MM region. This novel QM/MM border scheme, implemented in the elastic polarizable environment method for polar covalent materials (covEPE), provides an accurate description of the local structure of zeolites and other silica based materials.

Modeling adsorption of the uranyl dication on the hydroxylated alpha-Al2O3(0001) surface in an aqueous medium. Density functional study.

As a first step toward modeling the interaction of dissolved actinide contaminants with mineral surfaces, we studied low-coverage adsorption of aqueous uranyl, UO2(2+), on the hydroxylated alpha-Al2O3(0001) surface. We carried out density functional periodic slab model calculations and modeled solvation effects by explicit aqua ligands. We explored the formation of both inner- and outer-sphere complexes and estimated the corresponding adsorption energies.

Density-functional model cluster studies of EPR g tensors of Fs+ centers on the surface of MgO.

We report g tensors of surface color centers, so-called F(s) (+) centers, of MgO calculated with two density-functional approaches using accurately embedded cluster models. In line with recent UHV measurements on single-crystalline MgO film, we determined only small g-tensor anisotropies and negative shifts Deltag identical with g-g(e) for all F(s) (+) sites considered, namely, (001)-terrace, step, edge, and corner sites. The g values are very sensitive to the local structure of the defect: relaxation reverses the sign of Deltag.

Comparison of all sites for Ti substitution in zeolite TS-1 by an accurate embedded-cluster method.

We studied the preferential location of Ti centers in the framework of the Ti-containing MFI zeolite TS-1 using a hybrid DFT/MM embedding method developed recently. This "covalent elastic polarizable environment" (covEPE) cluster embedding allows a complete and self-consistent treatment of solid covalent systems such as zeolites. For the present study, we used a gradient-corrected density functional approach.

Single d-metal atoms on F(s) and F(s+) defects of MgO(001): a theoretical study across the periodic table.

Single d-metal atoms on oxygen defects F(s) and F(s+) of the MgO(001) surface were studied theoretically. We employed an accurate density functional method combined with cluster models, embedded in an elastic polarizable environment, and we applied two gradient-corrected exchange-correlation functionals. In this way, we quantified how 17 metal atoms from groups 6-11 of the periodic table (Cu, Ag, Au; Ni, Pd, Pt; Co, Rh, Ir; Fe, Ru, Os; Mn, Re; and Cr, Mo, W) interact with terrace sites of MgO.

Effects of the Aluminum Content of a Zeolite Framework: A DFT/MM Hybrid Approach Based on Cluster Models Embedded in an Elastic Polarizable Environment.

We report the first computational study with a sophisticated quantum mechanics/molecular mechanics (QM/MM) technique that addresses the effect of the aluminum content on the properties of acidic zeolites. To account for both electrostatic and mechanical interaction between the QM cluster and its MM environment, we used cluster models embedded in the covalent variant of the elastic polarizable environment (covEPE) [Nasluzov, V. A.

Study of the Electronic Structure of Ni(eta(5)-C(5)H(5))(NO) by Variable-Photon-Energy Photoelectron Spectroscopy and Density Functional Calculations.

Photoelectron spectra, with photon energies varying from 18 to 120 eV, have been measured for Ni(eta(5)-C(5)H(5))(NO). Relative partial photoelectron cross sections and branching ratios have been evaluated for the first three valence ionization bands. He I and He II photoelectron spectra have been remeasured for Ni(eta(5)-C(5)H(5))(NO) and Ni(eta(5)-C(5)H(4)CH(3))(NO).