Selectivity of vibronic coupling in complex molecules with benzene fragments

This paper deals with the mechanisms of localization of Franck-Condon vibronic coupling of πσ^*- or πlπ^*-orbital type in a few vibrational modes, (LVM) in excited electronic states of polyatomic molecules. The analysis of vibronic coupling uses highly symmetric basis sets (for representing MO structures and normal coordinates ξ_R) as well as simplified models that relate the shift Δ_R of the electron potential minima along the normal coordinates to the MO structure and to ξ_R in the form of analytical expressions. The modes that are active in LVM are determined from the experimental luminescence spectra. These ideas about approximately high local symmetry of vibronic coupling in benzene fragments as well as the estimates of Δ_R depending on variations in the MO structure explain the experimental results. L. Ya. Karpov Physicochemical Scientific Research Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 286–291, March–April, 1995. Translated by L. Smolina     

Algorithm for determination of the local similarity of molecules

An algorithm for seeking common structural fragments in compounds of different classes is developed. The algorithm allows for the molecular geometry and atomic characteristics, It may be used for recognition of compounds with properties associated with the local similarity of molecules such as ligand complementarity to a receptor. An example of seeking common structural elements for nondrug analgesics (para-acetamidophenol, acetylsalicylic acid, and amidopyrine) is given. I. I. Polzunov Altai State Technical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1083–1087, November–December, 1995. Translated by L. Smolina     

Algorithm for variational calculations of molecular symmetry in solving anharmonic vibrational problems

A universal program for variational calculations of molecular symmetry in solving anharmonic vibrational problems, realized by the author, is described. The program uses the group-theoretical method. Symmetrized basis wave functions are constructed with the aid of the generalized KJebsch-Gordan series suggested by the author. The method of constructing symmetrized basis wave functions and the program for adequate calculations of molecular symmetry were verified for many molecules of different symmetry groups: O_h, O, T_d, T_h, T, D_∞h, C_t8v, D_nd, D_nh, D_n, C_nv, C_nh, S_2n, C_n, C_i, C_s, and C₁ where 2 ≤n ≤6. It was confirmed that the program provides correct results and high-speed operation. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1146–1153, November–December, 1997.     

Electronic absorption spectrum of pyridine N-oxide in the gas phase. General characterization

The full electronic absorption spectrum of pyridine N-oxide vapor in the near ultraviolet region has been obtained. The vibronic structure has been analyzed in detail. The four absorption bands, which are observed at 341, 290, 228, and 217 nm, correspond to four 0–0 vibronic transitions. The spectrum is interpreted in terms of the CNDO/S method. The symmetry of the vibrations that exhibit activity due to the Herzberg-Teller effect in different electronic states has been studied. N. G. Chernyshevskii Saratov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 345–349, March–April, 1995. Translated by I. Izvekova     

“Perfect” structure regions in amorphous argon

The structure of molecular dynamic models of amorphous argon is investigated by the Voronoi-Delaunay method. It is shown that the majority of Delaunay simplices (determined by quadruplets of the nearest atoms) are “perfect,” i.e., close in their shape either to the ideal tetrahedron or to the ideal quartoctahedron. These two types of structural elements are positioned in a correlated manner relative to each other, forming regions of a “perfect” structure which, however, is not crystalline. The regions themselves are separated by sections of an “imperfect” structure in which the shape of simplicial atomic configurations differs from the mentioned ideal forms. Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 53–63, January–February, 1994. Translated by L. Chernomorskaya     

Determination of molecular constants of yttrium triiodide from electron diffraction data

Among the molecular constants needed for calculating the thermodynamic properties of yttrium triiodide, onlyR(Y- I) measured in the 1950s by electron diffractometry with a high error are available in the literature [1]. It was assumed that the geometrical configuration of YI₃ has D_3h symmetry. In [2] it was attempted to estimate the vibration frequencies of yttrium triiodide (the errors are not given and are thought to be more than 15%). To refine the available data in the framework of our program of molecular constant determination for transition metal iodides, we investigated the structure of yttrium triiodide by gas phase electron diffractometry. This paper deals with the results of this study. Translated fromZhurnal Strukturnoi Khimii Vol. 38, No. 1, pp. 203–206, January–February, 1997.     

Complementarity and justification in science,or comments on some fundamental concepts and problems in the theory and methods of structure and property investigations of complex molecules and molecular systems

Major problems in using some key notions of the theory of structure, such as bond length and potential function parameters, are discussed on the basis of the general complementarity principle formulated by Bohr. It is shown that the use of this principle and model representations, indispensable in microworld studies, inevitably involves subjectivism arising in the solution of inverse problems, and leads to the violation of the requirement of reason. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 123–134, July–August, 1994. Translated by O. Kharlamova     

Simultaneous electron diffraction and mass spectrometric studies of molecular structure of manganese trifluoride

It is shown that two geometrical models of the MnF₃ molecule equally fit experimental electron diffraction data: a pyramidal model of C_3v symmetry and a planar model with nonequivalent F-F distances of C_2v symmetry. Ivanovo Chemical Technological Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4. pp. 61–67, July–August, 1994. Translated by L. Smolina     

Theory of lineshape in photoelectron and Auger spectra

A theory of lineshape in photoelectron spectra is developed based on the Green’s function calculation of the atomic vacancy structure. It is shown that the broadening of photoelectron lines is always somewhat asymmetrical, and the broadening of satellite lines arising in atomic photoionization is generally strongly asymmetrical and inverse. The approach is generalized to low-energy Auger spectra; it is shown that Auger decay lines of excited atomic states may narrow with respect to the width of the initial level. The results are compared with experimental photoelectron spectra. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 985–991, November–December, 1998.     

Separation of the vibrational,rotational, and translational motions of polyatomic molecules using curvilinear vibrational coordinates

A new method is suggested for separating the vibrational, rotational, and translational motions of polyatomic molecules using curvilinear vibrational coordinates that are linear with respect to the natural vibrational coordinates. It is shown that, in this case, Coriolis interactions between the vibrational and rotational motions are absent. The solutions of the anharmonic vibrational-rotational problems in the curvilinear and linear vibrational coordinates are compared. The absence of Coriolis interactions between the vibrational and rotational motions in the curvilinear vibrational coordinates is proved numerically. The same conclusion is additionally supported by calculations of the anharmonic vibrational energy levels for the H₂O, H₂S, NO₂, SO₂, and ClO₂ molecules in the linear and curvilinear vibrational coordinates using the Hamiltonian designed in the curvilinear vibrational coordinates with and without Coriolis vibrational-rotational interactions. Volgograd Pedagogical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 239–254, March–April, 1995. Translated by I. Izvekova     

Virtual geometrical symmetry group of a nonrigid molecule with energetically nonequivalent equilibrium configurations

The notion of a virtual geometrical symmetry group of a nonrigid molecule with energetically nonequivalent equilibrium configurations is introduced. Due to this, methods of qualitative analysis of intramolecular effects for such molecules using the concept of symmetry group chains are significantly generalized. Insitute of Applied Physics, Novgorod. Translated fromZhumal Struckturmoi Khimii, Vol. 37, No. 3, pp. 432–439, May–June, 1996.     

Construction of basis sets of hybrid atomic orbitals for describing the nonequivalent bonds of an atom with three neighboring atoms (sp 2 andsp 3 hybridization)

The paper describes methods for obtaining basis sets of sp² and sp³ hybrid atomic orbitals to describe nonequivalent chemical bonds in organic molecules with heteroatoms. Being affine, these basis sets present an alternative to the conventional basis sets of Cartesian atomic orbitals. Unlike the latter, the hybrid atomic orbitals are invariant to spatial rotations of molecules, thus providing the rotational invariance of the results of any semiempirical quantum chemical calculations. The construction of the basis sets of hybrid functions for atoms surrounded with three neighboring atoms (planar and nonplanar configurations) is considered in detail. V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36. No. 6, pp. 963–968, November–December, 1995. Translated by I. Izvekova     

Combining X-ray scattering and exafs experiments for studying amorphous alloys of 3d transition metals with zirconium

The atomic structure of the amorphous alloys of several transition metals (Fe, Co, Ni, and Cu) with zirconium is studied in terms of partial paired correlation functions. The short-range order parameters, namely, the shortest interatomic distances, coordination numbers, and the form of distribution functions, are compared and a correlation between the atomic structure and the interaction between atoms of different sorts is established. The study offers the possibility to model the spatial distribution of atoms and the physical properties of the analyzed alloys and predict the properties of new systems. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1025–1030, November–December, 1998.     

Computational modeling of amorphous silica. 2. Modeling the initial structures. Aerosil

A qualitative algorithm for constructing large clusters of aerosil model structures is used. According to this algorithm and the classification of amorphous silicas, aerosil is classified with tectosilicas, which are characterized by close packing of silicon-oxygen tetrahedra. Two quantitative algorithms for constructing large close-packed clusters are proposed. The structures of the clusters having from 10 to 24 silicon atoms, completely optimized by quantum chemical methods, were obtained. Small, medium, and large clusters for modeling the local and collective properties of atomic and functional group packing in the aerosil structure are distinguished. Institute of Surface Chemistry, Ukrainian Academy of Sciences. Russian University of Peoples' Friendship. Translated fromZhurnal Struktumoi Khimii, Vol. 35, No. 3, pp. 16–26, May–June, 1994. Translated by O. Kharlamova     

Radiographic study of the phase formation process in obtaining KNbO3

Instability in the formation of KNbO₃ with perovskite structure is complicated by its structural instability. The structural instability accounts for the existence of phases different in their symmetry and cell parameters (rhombic, tetragonal, and cubic) at room temperature. Original Russian Text Copyright ? 2009 by Yu. A. Kuprina, P. Yu. Teslenko, N. B. Kofanova, M. F. Kupriyanov, and Yu. V. Kabirov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 3, pp. 582–586, May–June, 2009.     

Study of the electronic structure of organogermanes with extended coordination sphere of germanium

The spatial and electronic structures of some organogermanes with extended coordination spheres of the metal were calculated using AMPAC and HYPER CHEM 4.0 program packages. Interatomic distances, bond angles, torsion angles, atomic charges, electron densities, bond orders, parameters of localized and canonical molecular orbitals,etc. were determined. The nature of the additional intramolecular O→Ge interaction in the molecules of these compounds was considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 383–387, March, 1998.     

An approximate method of self-consistent electronic structure calculations of a crystal surface. The Ir(111) surface

The Slater approximation for atomic electron energies is employed to calculate the electronic structure of the Ir(111) surface. The results are used to estimate the shift of the 4f_7/2 level on the surface relative to its position in the volume. The electron state densities in the neighborhood of the center of the surface Brillouin zone (SBZ) are compared with photoelectronic spectra for emission normal to the Ir(111) surface. On this basis, the accuracy of this approximation is estimated. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 17–24, January–February, 1994. Translated by O. Kharlamova     

Construction of basis sets of hybrid atomic orbitals for describing the nonequivalent bonds of an atom with four neighboring atoms (sp 3 hybridization)

Methods for constructing the basis sets of sp³ hybrid atomic orbitals for atoms surrounded with four neighboring atoms are discussed in detail. The results obtained are generalized as a theorem of sp³ hybridization. A general method is proposed for constructing basis sets of orthogonal sp³ hybrid atomic orbitals for atoms with distorted tetrahedral environments. V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp.969–975, November–December, 1995. Translated by I. Izvekova     

Comparative study of the structures of some basic iron(III) sulfates

IR and EXAFS spectroscopies were used to study the products of the hydrolysis of iron(III) sulfate. A hypothesis for the structure of amorphous basic iron sulfate is made from a comparison of its IR spectra and radial atomic distribution curves with the corresponding data for jarosite. Analysis of the interatomic distances and manifestations of the sulfate ion in the low- and high-temperature IR spectra shows that in the amorphous product of the hydrolysis, unlike in the jarosite, the sulfate ion is not involved in the first coordination sphere of the iron atoms, but is held in the structure by hydrogen bonds. Reasons for the high catalyzing ability of the amorphous basic iron sulfate are suggested. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurmal Strukturnoi Khimii, Vol. 37, No. 2, pp. 275–282, March–April, 1996. Translated by I. Izvekova