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The electronic structures of [(RuCp-(PPh3))2(mu2-(1,4-eta:3,6-eta)Te6)] and [(RuCp(PPh3))2-(mu2-(1,4-eta:3,6-eta)Te6].CH2Cl2 are analyzed with the use of first principles density functional theory. Bond order analysis indicates that the Te-Te bond where fusion occurs has a shared bonding charge of about 2/3 of that found for Te-Te single bonds.

Eleven new quaternary rare-earth tellurides, CsLnZnTe3 (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Y), were prepared from solid-state reactions at 1123 K. The isostructural materials crystalline in the layered KZCuS3 structure type in the orthorhombic space group Cmcm.

The use of direct method analysis and density functional theory (DFT) for the (001) crystal face of SrTio3 with the solution of a c(4x2) unit cell is mentioned. The surface is characterized by a single TiO2 overlayer in which Ti atoms are arranged into edge-shared truncated octahedra.

Research has been conducted on the isostructural RbLnSe (sub)2 compounds. These compounds has been synthesized via the reactive flux methods and their crystal structure, magnetic and optical properties have been studied and are discussed.

Author(s): Natasha Erdman [1]; Kenneth R. Poeppelmeier [2]; Mark Asta [3]; Oliver Warschkow [4]; Donald E. Ellis [4]; Laurence D. Marks (corresponding author) [1] Oxide surfaces are important for applications [...]

The structure, electrical, magnetic, and spectroscopic characteristics of the novel molecular metal tetrabenzoporphyrin iodide (H2(tbp)I) as well as that of nickeltetrabenzpoprphyrin (Ni(tbp)I) were described. Single-crystal reflectance spectroscopy, electrical conductivity, magnetic susceptibility, and electron paramagnetic resonance were utilized. Data revealed that H2(tbp)I and Ni(tbp)I have the same EPR values. The electrical conductivity as well as the Curie constant for Ni(tbp)I were higher than that of H2(tbp)I secondary to the crystal defects and organic impurities.

“Molecular squares” formed from Re(CO)3Cl corners and porphyrin sides have potential applications as hosts for catalytic sites and as building blocks for membranes. In these materials, knowledge of the conformations of the squares is important. Molecular-mechanics (MM) and density-functional (DF) calculations have been used iteratively in this work to find the minimum-energy configurations of several porphyrin molecular squares. MM predicts that the steric and torsional interactions at connecting junctures of the square framework determine the overall geometry. Torsional degrees of freedom around these junctures were therefore analyzed using DF methods, giving further insight and helping choose among MM force-field options. Single-point DF calculations on the entire squares showed that the energy and conformation of the entire square could be reliably obtained by performing DF calculations on the critical elements of the square and then piecing them together. This “piecewise” strategy allows for both the major torsional motions and the most important local relaxations of large supramolecular species such as molecular squares. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The preparations of seven new isostructural uranium chalcogenides AMU[Q.sub.3] compounds (where A = alkali metal, M = Cu or Ag, Q = S or Se) via solid-state reactions are reported. The compounds are found to be semiconductors with optical band gaps smaller than 0.73 eV and density-of-state analysis revealed the M-Q orbital to overlap in the valence band and U-Q orbital to overlap in the conduction band.

Spin-polarized calculations of tetrahedral Fe4, Ni4, and Co4 clusters have been performed by the self-consistent field discrete variational Xα method. Partially carbonylated C3v clusters Co4(μ-CO)3 and (OC)3CoCo3(μ-CO)3 have also been examined to explore how magnetic moments vary with cluster coordination environment. The bare tetrahedral clusters are magnetic containing 12, 6, and 2 unpaired electrons for Fe4, Co4, and Ni4, respectively. Exchange splittings also decrease (2.68, 1.60, and 0.56 eV) along this series. Analysis of density of states plots for these clusters supports the notion that 4s and 4p mixing into the metal d band yields hybrid orbitals better suited for metal–metal bonding. Electronic transitions are predicted to occur in the near IR absorption spectra of the M4 clusters, a region yet to be studied experimentally. Calculations for C3v Co4(μ-Co)3 yield six unpaired electrons with a large spin density on the unligated apical cobalt. In (OC)3CoCo3(μ-CO)3, where the apical cobalt is coordinately saturated, all the spin density (four unpaired electrons) is localized in the basal plane. Bridging CO groups in the basal plan are antiferromagnetically coupled to cobalt. [ABSTRACT FROM AUTHOR]

Research has been conducted on bismuth chalcogenides, AMBiS (sub)4 where A is rubidium and/or cesium and M is silicon and/or germanium. The syntheses and structures of these compounds have been carried our, and the results are reported.

Abstract: The structure sensitivity of Pt nanoparticles (PtN) for gas‐phase acrolein (AC) hydrogenation was probed for PtN on BaxSr1−xTiO3 nanocuboid supports with (0 0 1) facets in a combined theoretical and experimental study. The in situ selectivity for allyl alcohol increased with the increase of the Sr concentration in the support, which corresponds to modifications in the stable Winterbottom shape and lattice strain of the Pt nanoparticles as a result of the interfacial energy between Pt and the BaxSr1−xTiO3 supports. “Local model” nanofacets of the Pt surface, edge, and corner morphologies were developed as compact representations of adsorption and reaction sites. DFT was used as the primary modeling tool for the equilibrium adsorption states. We argue that adsorption on edge sites is critically important for the overall allyl alcohol selectivity of PtN catalysts. A simple model was developed to represent PtN strain effects caused by its interaction with the substrate. Bader topological atom, spherical volume averaging charge, and modified bond valence sum analyses were used to understand the bonding structure. Density of states analysis was performed for the structures of PtN, adsorbed AC, and intermediate products to examine adsorbate–particle interactions. The simulated hydrogenation of AC on PtN nanofacets was compared to the in situ hydrogenation of AC by PtN on BaxSr1−xTiO3 to examine the effects of facet, edge, and corner sites on the overall selectivity. [ABSTRACT FROM AUTHOR]

The bixbyite structure of In2O3 has two nonequivalent, 6-coordinate cation sites and, when Sn is doped into In2O3, the Sn prefers the "b-site" and produces a highly conductive material. When divalent/tetravalent cation pairs are cosubstituted into In2O3, however, the conductivity increases to a lesser extent and the site occupancy is less understood. We examine the site occupancy in the MgxIn2-xSnxO3 and ZnxIn2-2xSnxO3 systems with high resolution X-ray and neutron diffraction and density functional theory computations, respectively. In these sample cases and those that are previously reported in the MxIn2-2xSnxO3 (M = Cu, Ni, or Zn) systems, the solubility limit is greater than 25%, ensuring that the b-site cannot be the exclusively preferred site as it is in Sn:In2O3. Prior to this saturation point, we report that the M2+ cation always has at least a partial occupancy on the d-site and the Sn4+ cation has at least a partial occupancy on the b-site. The energies of formation for these configurations are highly favored, and prefer that the divalent and tetravalent substitutes are adjacent in the crystal lattice, which suggests short range ordering. Diffuse reflectance and 4-point probe measurements of MgxIn2-xSnxO3 demonstrate that it can maintain an optical band gap >2.8 eV while surpassing 1000 S/cm in conductivity. Understanding how multiple constituents occupy the two nonequivalent cation sites can provide information on how to optimize cosubstituted systems to increase Sn solubility while maintaining its dopant nature, achieving maximum conductivity. [ABSTRACT FROM AUTHOR]

A new software package, RASPA, for simulating adsorption and diffusion of molecules in flexible nanoporous materials is presented. The code implements the latest state-of-the-art algorithms for molecular dynamics and Monte Carlo (MC) in various ensembles including symplectic/measure-preserving integrators, Ewald summation, configurational-bias MC, continuous fractional component MC, reactive MC and Baker's minimisation. We show example applications of RASPA in computing coexistence properties, adsorption isotherms for single and multiple components, self- and collective diffusivities, reaction systems and visualisation. The software is released under the GNU General Public License. [ABSTRACT FROM PUBLISHER]