Alexey I. Baranov

Electron localization and delocalization indices for solids

The electron localization and delocalization indices obtained by the integration of exchange‐correlation part of pair density over chemically meaningful regions of space, e.g., QTAIM atoms are valuable tools for the bonding analysis in molecular systems. However, among periodic systems only few simplest models were analyzed with this approach until now. This contribution reports implementation and evaluation of the localization and delocalization indices on the basis of solid state DFT calculations. A comparison with the results of simple analytical model of Ponec was made. In addition, a small set of compounds with ionic (NaCl), covalent (diamond, graphite), and metallic (Na, Cu) bonding interactions was characterized using this method. Typical features of different types of bonding were discussed using the delocalization indices.

Neutral Tellurium Rings in the Coordination Polymers [Ru(Te9)](InCl4)2, [Ru(Te8)]Cl2, and [Rh(Te6)]Cl3

Shiny black, air-insensitive crystals of tellurium-rich one-dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl(4). The compounds [Ru(Te(9))](InCl(4))(2) and [Ru(Te(8))]Cl(2) crystallize in the monoclinic space group type C2/c, whereas [Rh(Te(6))]Cl(3) adopts the trigonal space group type R ̅3c. In the crystal structures, linear, positively charged [M(m+) (Te(n)(±0))] (M=Ru, m=2; Rh, m=3) chains run parallel to the c axes. Each of the uncharged Te(n) molecules (n=6, 8, 9) coordinates two transition-metal atoms as a bridging bis-tridentate ligand. Because the coordinating tellurium atoms act as electron-pair donors, the 18-electron rule is fulfilled for the octahedrally coordinated transition-metal cations. Based on DFT calculations, the quantum theory of atoms in molecules (QTAIM) and the electron localizability indicator (ELI) provide insight into the principles of the polar donor bonding in these complexes. Comparison with optimized ring geometries reveals substantial tension in the coordinating tellurium molecules.

Dumbbells of Five-Connected Silicon Atoms and Superconductivity in the Binary Silicides MSi3 (M = Ca, Y, Lu)

The new metastable binary silicides MSi(3) (M = Ca, Y, Lu) have been synthesized by high-pressure, high-temperature reactions at pressures between 12(2) and 15(2) GPa and temperatures from 900(100) to 1400(150) K. The atomic patterns comprise intricate silicon layers of condensed molecule-like Si(2) dimers. The alkaline-earth element adopts the oxidation state +2, while the rare-earth and transition metals realize +3. All of the compounds exhibit BCS-type superconductivity with weak electron-phonon coupling below critical temperatures of up to 7 K.

Domain-averaged Fermi-hole analysis for solids

The domain-averaged Fermi hole (DAFH) orbitals provide highly visual representation of bonding in terms of orbital-like functions with attributed occupation numbers. It was successfully applied on many molecular systems including those with non-trivial bonding patterns. This article reports for the first time the extension of the DAFH analysis to the realm of extended periodic systems. Simple analytical model of DAFH orbital for single-band solids is introduced which allows to rationalize typical features that DAFH orbitals for extended systems may possess. In particular, a connection between Wannier and DAFH orbitals has been analyzed. The analysis of DAFH orbitals on the basis of DFT calculations is applied to hydrogen lattices of different dimensions as well as to the solids diamond, graphite, Na, Cu and NaCl. In case of hydrogen lattices, remarkable similarity is found between the DAFH orbitals evaluated with both the analytical approach and DFT. In case of the selected ionic and covalent solids the DAFH orbitals deliver bonding descriptions, which are compatible with classical orbital interpretation. For metals the DAFH analysis shows essential multicenter nature of bonding.

Sr2Ni3—A Strontium Subnickelide?

In the course of our current research on quaternary phases in the systems Sr-Ni-C-N, we are also interested in binary phases of the system Sr Ni, in order to use them starting material for reactions. The binary system Sr Ni was first investigated in 1966. According to this study, SrNi is the only intermediate phase. Our recent investigation of the same system (Figure 1) did not confirm the existence of

Electron localizability for hexagonal element structures

For 21 elements crystallizing in hexagonal structure density functional calculations were performed. The topology of the electron localizability indicator (ELI) allows classifying the elements as appertaining to one of six patterns. The bifurcation diagrams as well as the electron populations in ELI basins for each pattern are discussed.

Spatial chemistry of the aluminium-platinum compounds: a quantum chemical approach

It was shown by quantum chemical calculations (TB-LMTO-ASA) for the compounds of the system aluminium—platinum that the Baders atomic volumes and charges of platinum and aluminium atoms change with the concentration. This behaviour is in contrast to Vegards approach which assumes constant volume increments of the constituents in the whole concentration region. Introduc ing the variation of the atomic volume with the composition extends the Vegards approach and allows non-linear and even non-monotonic slope of the atomic volume vs concentration dependency, which is observed experimentally in several systems.

A Metallic Room‐Temperature Oxide Ion Conductor

Nanoparticles of Bi3 Ir, obtained from a microwave-assisted polyol process, activate molecular oxygen from air at room temperature and reversibly intercalate it as oxide ions. The closely related structures of Bi3 Ir and Bi3 IrOx (x≤2) were investigated by X-ray diffraction, electron microscopy, and quantum-chemical modeling. In the topochemically formed metallic suboxide, the intermetallic building units are fully preserved. Time- and temperature-dependent monitoring of the oxygen uptake in an oxygen-filled chamber shows that the activation energy for oxide diffusion (84 meV) is one order of magnitude smaller than that in any known material. Bi3 IrOx is the first metallic oxide ion conductor and also the first that operates at room temperature.

Atomic interactions in the intermetallic catalyst GaPd

ABSTRACT Chemical bonding in the highly selective hydrogenation catalyst GaPd is analysed by means of quantum chemical calculations employing the bonding analysis techniques in real space, in particular the quantum theory of atoms in molecules, the delocalisation indices and the electron localisability approach. A three-dimensional system of predominantly two-centre electron-deficient Ga–Pd interactions is revealed, being responsible for the high stability of the compound under hydrogenation conditions.

Electron localizability indicators from spinor wavefunctions.

For the fully relativistic 4‐component many‐electron wavefunction six flavors of electron localizability indicators (ELI) have been proposed. Their counterparts, suitable for the application to the 2‐component wavefunctions, have been also derived. Six proposed indicators have been tested on Ar and Rn atoms and one of them, the ELI‐D for spatially antisymmetrized electron pairs, has been found to reveal atomic shell structures at quantitative level. Shell structures of all the atoms of periods 4–7 of the periodic table have been obtained using this indicator and compared with these obtained from the nonrelativistic limit calculations as well as from scalar‐relativistic (zero‐order regular approximation) calculations.