Spectrum of states in icosahedral structures of the electronic configuration gn (N = 1–7). 1. Invariant expansion for integrals and energiesPlakhutin, B. N.
doi: 10.1007/bf02768800pmid: N/A
The energy spectrum of the states that appear in structures of icosahedral (I,Ih symmetry with open electronic shells gN (dim g = 4; N = 1–7) is reported. The energies are obtained in terms of integral invariants (reduced matrix elements of electron-electron interaction) Hk (g, g). The latter are analogs of the Slater-Condon parameters Fk(l,l) for atoms with the lN electronic configuration. A similar representation is proposed for the integrals mm’≨’) of electron-electron interaction on the 4-fold degenerate g orbitals in the “standard” representation. The relation between the terms of the gN(I,Ih) configuration and the parent states of the orthogonal group O+(4) is discussed.
Semiempirical andab initio calculations of the full configuration interaction using iterated Krylov’s spacesIvanov, V. V.; Luzanov, A. V.
doi: 10.1007/bf02768801pmid: N/A
The algorithm proposed previously for calculating the full configuration interaction using the variation matrix of the wave operator involves the numerical solution of the corresponding incomplete eigenvalue problem based on iterated Krylov’s subspaces. In practice, that means using the multistep gradient method as a special version of the Lanczos method. The high efficiency of this algorithm, which can readily be used in personal computer calculations, is proved by particular ab initio calculations of the full configuration interaction for the helium and beryllium atoms as well as by semiempirical calculations of π-shells for naphthalene and diphenylene. The algorithm is of particular assistance in obtaining numerous excited states, which are used for determining various spectral sums (polarizability, van der Waals interaction constants, and photoionization cross sections).
Chemical bond and electronic structure anisotropies in the graphitic and rhombohedral modifications of boron nitrideGrinyaev, S. N.; Lopatin, V. V.
doi: 10.1007/bf02768803pmid: N/A
The pseudopotential method is used to calculate the band spectra, valence charge densities, and electroneutrality levels in the graphitic (h-BN) and rhombohedral (r-BN) modifications of boron nitride. It is shown that these compounds are indirect-band insulators with the minimum energies of the indirect (4.65 and 4.8 eV) and direct (5.27 and 5.5 eV) forbidden zones in h- and r-BN, respectively. The band energies of h-BN correlate well with the experimental data. Both crystals are characterized by ionic-covalent chemical bonds. In the plane of hexagonal layers, the bonds are more covalent in h-BN. In h- and r-BN, the electroneutrality levels correspond to the energy of about 1.9 eV over the top of the valence band, which is responsible for the hole conductivity of the substances. In superlattices based on these compounds, the rhombohedral phase is a quantum well for holes and a barrier for electrons.
Quantum chemical treatment of the structure and absorption spectra of 1,1-diphenylpropyllithium and its complexesKalninsh, K. K.
doi: 10.1007/bf02768806pmid: N/A
The spatial and electronic structure and absorption spectra of butyllithium, 1-phenylpropyllithium, and 1,1-diphenylpropyllithium and their anionic and radical forms are calculated. Ionization potentials are low (about 6 eV) for all the organolithium compounds. The low-frequency electron transition in the visible range of the spectra of aromatic organolithium compounds is due to the electron density transfer from the α-carbon atom to the aromatic rings. Complexes of 1,1-diphenylpropyllithium with methylbenzoate and acetophenone, possessing low electron affinity (0.92 and 0.9 eV), are considered It is assumed that thermal electron transition occurs in the excited triplet state of the complex and is accompanied by a removal of the Li+ cation. A comparison of the experimental spectrum of the polystyryl-l,l-diphenylethyllithium+methylbenzoate reaction system with the calculated spectra of the MB.-and AP.-radical onions and MB.Li and AP.Li radicals showed that the best agreement is observed for AP.Li.
Simultaneous electron diffraction and mass-spectrometric study of the structure of the MoF5 moleculeGiricheva, N. I.; Krasnova, O. G.; Girichev, G. V.
doi: 10.1007/bf02768807pmid: N/A
Electron diffraction data for the MoF5 molecule are analyzed in terms of an ra structure. Three models of the geometrical structure, which have D3h, C4v, and C2v symmetry, are considered. It is confirmed that a distorted bipyramid of C2v symmetry is the best model that is in agreement with experimental electron diffraction data. The model has three different types of nuclear Mo-F distances: rα(Mo-F1eq) = 1.720(5) Å, rα(Mo-F2eq) = 1.826(7) Å, rα(Mo-Fax) = 1.825(7) Å. The bond angle between the pseudoaxial bonds is 168.1(0.6)‡, and the angle between the Mo-F2eq pseudoequatorial bonds is 122.6(0.8)‡. The ra(Mo-Fleq) and ra(Mo-F2eq) distances differ significantly. Possible reasons for this are discussed.
Orientational ordering, conformation, and polarizability of molecules in the reentrant phase of discoid nematicsAverianov, E. M.
doi: 10.1007/bf02768809pmid: N/A
This paper presents data on orientational ordering in a reentrant discoid nematic and on changes in the polarizability of discogenic molecules in a homologous series. The phase transition of a nematic to the discotic column phase is accompanied by a jump of the orientational ordering parameter and is characterized by close relationship between the orientational and translational ordering of molecules. The lengthening of the flexible peripheral molecular chains in the reentrant nematic phase considerably changes their conformational state, decreasing the anisotropy of their polarizability.