Electronic structure and bonding of ozone

The ground and low-lying states of ozone (O(3)) have been studied by multireference variational methods and large basis sets. We have constructed potential energy curves along the bending coordinate for (1,2) (1)A('), (1,2) (1)A("), (1,2) (3)A('), and (1,2) (3)A(") symmetries, optimizing at the same time the symmetric stretching coordinate. Thirteen minima have been located whose geometrical and energetic characteristics are in very good agreement with existing experimental data. Special emphasis has been given to the interpretation of the chemical bond through valence-bond-Lewis diagrams; their appropriate use captures admirably the bonding nature of the O(3) molecule. The biradical character of its ground state, adopted long ago by the scientific community, does not follow from a careful analysis of its wave function.     

Electronic structure and chemical bonding in lanthanide titanates

Institute of Chemistry, Ural Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 6, pp. 25–31, November–December, 1990.     

Electronic structure and bonding in clusters: Theoretical studies

The electronic structures of small Al _n ,n=5, 9, 13, clusters with bulk geometry are studied using the ab initio Hartree-Fock-LCAO method. The cluster ground states have always multiplicity higher than the lowest possible value. However, the energy difference between ground and lowest low spin state decreases with increasing cluster size. The energy range of the Al _n cluster valence levels is comparable with the width of the occupied part of the 3sp band in bulk Al. The different binding mechanisms that arise when a CO molecule interacts with Al _n clusters in different coordination sites are analyzed in detail with the constrained space orbital variation (CSOV) method. Electrostatic and polarization contributions to the interaction are found to be important. Among charge transfer (donation) contributions π electron transfer from Al _n to CO corresponding to π backbonding is energetically more important than σ electron transfer from CO to Al _n characterizing the σ bond.     

Electronic structure and chemical bonding in bismuth sesquioxide polymorphs

The electronic structure of the α-Bi₂O₃, Β-Bi₂O₃, and γ-Bi₂O₃ phases was investigated by the ab initio self-consistent LMTO method in a tight binding approximation and by the semiempirical Hückel method. The total and partial densities of states and Mulliken overlap populations were obtained. The stability of bismuth oxide polymorphs is discussed based on the results of the total energy calculations for crystals. An analysis of chemical bonding shows that the Bi-O interaction plays the leading role. The Bi-Bi metallic bond is absent. Mechanisms of oxygen ion migration and possible stabilization of the structure of the superionic conductor δ-Bi₂O₃ are discussed.     

Electronic structure and chemical bonding in nonstoichiometric zirconium nitrides

X-ray emission spectra were taken and band calculations using the Green function LMTO method and cluster calculations using the discrete variational X method were carried out for the electronic structure and chemical bonding parameters for nonstoichiometric zirconium nitrides containing metallic and metalloid vacancies. The existence of structural defects leads to a redistribution of the occupancies of the major sub-bands of the nitride valence spectrum and the formation of a new group of states between the p-d- and d-like bands of ZrN_1.0.Institute of Chemistry, Urals Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 5, pp. 82–89, September–October, 1989.     

Electronic structure and chemical bonding in Ba-Cu-O layer systems

The cluster method of discrete variation was used to study compounds containing chains of plane-coordinated copper ions separating oxygen-copper planes. We also examined real YBa₂Cu₃O₇ and hypothetical MBa₃Cu₄O₉ systems (M is a tetravalent metal ion). A study was carried out on the transformation of the valence band and structure of the molecular orbitals in the Fermi level in going from YBa₂Cu₃O₇ to MBa₃Cu₄O₉. The chemical bonding was analyzed and the role of the interchain interaction in the bonding of the copper and oxygen atoms in different crystallographic positions was determined.Institute of Chemistry, Urals Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 5, pp. 17–20, September–October, 1989.     

三元硼氮环的电子结构与成键

用从头算ＳＣＦ－ ＭＯ法对三元硼氮环２ 个系列８ 个分子的电子结构进行了研究．根据计算结果,由原子的轨道布居以及σ和π电子的分布,讨论了硼原子与氮原子间的成键情况．结果表明,硼原子和氮原子上加Ｈ 有利于环的稳定,同时削弱了Ｂ—Ｎ 键而增强了Ｂ—Ｂ键和Ｎ—Ｎ 键,对Ｂ２Ｎ 系列和ＢＮ２ 系列中的Ｂ原子和Ｎ 原子的净电荷的影响恰好相反．     

Electronic structure and bonding in actinyl ions and their analogs

This Feature Article seeks to present the current state of knowledge, both experimental and theoretical, of the electronic structure and bonding in actinyl ions and related species, such as the isoelectronic imido compounds as well as in linear triatomic actinide molecules of the type X-An-Y.     

Electronic structure and bonding in Si70

We report a detailed AM1 investigation of the geometrical and electronic structure of Si₇₀. For this purpose, bond lengths, bond orders, charges and molecular energy levels are widely analyzed, and compared with previous theoretical and experimental data on Si₆₀ and homologous carbon clusters C₇₀ and C₆₀. The predicted D_5h structure of Si₇₀ is less delocalized than that of C₇₀. Furthermore, Si₇₀ presents the lowest ionization potential (7.63eV), the highest electron affinity (3.61 eV) and the smallest HOMO-LUMO gap (4.02eV) of the four studied clusters.     

Electronic structure and bonding in the ground state of Cu2

Extended basis set calculations have been performed for the ground state of Cu₂ using CI(SD) and the coupled pair functional (CPF) method, a size-consistent modification of CI(SD). Special emphasis is given to the discussion of (i) basis saturation effects (up to g functions were included), (ii) effects of cluster corrections to achieve size consistency, (iii) relativistic effects, which were included in first order from the Cowan-Griffin operator. The final results are R_e = 4.23 au = 2.238 A, D_e = 1.84 eV, in close agreement with experimental values of 4.20 au = 2.22 A and 2.05 eV, respectively.     

Electronic structure of CO--an exercise in modern chemical bonding theory

This paper discusses recent progress that has been made in the understanding of the electronic structure and bonding situation of carbon monoxide which was analyzed using modern quantum chemical methods. The new results are compared with standard models of chemical bonding. The electronic charge distribution and the dipole moment, the nature of the HOMO and the bond dissociation energy are discussed in detail.     

Electronic structure and bonding of Be2

Laser-induced fluorescence of Be₂ produced by laser vaporization of the metal is observed and analyzed. The X¹Σ_g⁺ ground state is characterized by r_e = 2.45 A and D_e = 790 ± 30 cm^?1. The spectroscopic constants and lifetimes of the much more strongly bound A ¹Πu and B ¹Σ_g⁺ states are also obtained. The Be₂ molecular properties and bonding are discussed and compared with related species.     

Electronic structure and anisotropic chemical bonding in TiNF from ab initio study

Accounting for disorder in anatase titanium nitride fluoride TiNF is done through atoms re-distributions based on geometry optimizations using ultra soft pseudo potentials within density functional theory DFT. The fully geometry relaxed structures are found to keep the body centering of anatase (I4₁/amd No. 141). The new structural setups are identified with space groups I-4m2 No. 119 and Imm2 No. 44 which obey the “group to subgroup” relationships with respect to anatase. In the ground state Imm2 structure identified from energy differences, TiNF is found semi-conducting with similar density of states features to anatase TiO₂ and a chemical bonding differentiated between covalent like Ti-N versus ionic like Ti-F. Inter-anion N-F bonding is also identified.     

Electronic structure, chemical bonding, and spin polarization in ferromagnetic MnAl

The electronic structure of ferromagnetic τ-MnAl has been calculated using density-functional techniques (TB-LMTO-ASA, FLAPW) and quantum-chemically analyzed by means of the crystal orbital Hamilton population tool. While all observable quantities are in good agreement with experiment, the tetragonal structure of ferromagnetic MnAl is interpreted to arise from a nonmagnetic cubic structure by two subsequent steps, namely (a) an electronic distortion due to spin polarization followed by (b) a structural distortion into the tetragonal system. The various strengths of interatomic bonding have been calculated in order to elucidate the competition between electronic and structural distortion.     

Electronic structure and Chemical bonding in Sr4Nb17O26

The electronic structure of oxoniobate Sr₄Nb₁₇O₂₆ is studied by the linear muffintin orbital (LMTO) method. It is shown that the highenergy conduction band consists of the Nb4d states and the hybridized valence band is formed by the Nb4d and O2p states. The band structure of this compound is characterized by superposition of the bands of the 2p states of perovskite oxygen atoms and the 4d states of monoxide niobium atoms. The degree of oxidation of the perovskite and monoxide niobium atoms is +5 and +2.56, respectively. Chemical bonding is analyzed using the electron localization function and model Hückel calculations. The niobiumoxygen bond is shown to be the strongest. The Fermi level is localized in the vicinity of the bottom of the niobium antibonding state band, which explains the existence of Sr_4−xNb₁₇O₂₆ in the homogeneity region corresponding to 0 < x < 0.3. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 5, pp. 771–780, September–October, 1998. This work was supported by RFFR grant No. 96-03-32015a.     

Electronic structure and chemical bonding of δ-Bi2O3

The band structure of the fluorite-type δ-Bi₂O₃ was calculated by the linear LMTO methods in the approximation of overlapping atomic spheres using the basis set of orthogonal orbitals (LMTO-ASA) and by the full-potential LMTO method (LMTO-FP) for two vacancy orientations over a wide range of oxygen concentrations. The calculated parameters of chemical bonds—the binding energy E_bin and the pressure of the electron-nuclear system—show that the most stable compound is that with two vacancies per unit cell, oriented predominantly along the (111) direction. The hybrid Bi−O bonds are weak, and mostly the Bi−Bi bonds are responsible for the structural stabilization of δ-Bi₂O₃. The mechanism of the formation of a semiconductor gap in the band structure of δ-Bi₂O₃ is discussed. Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 1, pp. 48–58, January–February, 1996. Translated by I. Izvekova     

Electronic structure and peculiar bonding properties of NdNiMg5 from first principles

The newly found ternary compound NdNiMg₅ has been studied within DFT based methodologies. Results of cohesive energy, charge transfers, elastic constants and electron localized function mapping as well as electronic structure and bonding properties have been compared with those of isostructural binary NdNi. The calculation results have shown that Mg substructures interlayering NdNi – like slabs exhibit different magnitudes of charge transfers all within range of metallic behavior and the different Mg substructures selectively bind with Nd and Ni substructures. As a consequence an enhanced cohesion with respect to binary intermetallic NdNi is identified. The whole set of elastic constants and their combinations in orthorhombic symmetry confirm the mechanical stability of NdNiMg₅ with larger compressibility and less ductility (more brittleness) with respect substructures to NdNi. While in an intermetallic compound such as NdNi the bonding is ensured mainly by Nd–Ni interaction, in NdNiMg₅ Nd–Ni, Nd–Mg, Ni–Mg as well as Mg–Mg participate to the bonding and the extra electrons brought by Mg are found within bonding states thus illustrating furthermore the enhanced cohesion of the ternary versus the binary systems.