Modern development of x-ray technology allows to conduct a detailed study of multiphoton processes of absorption and scattering of x-ray photon by deep and subvalent shells of molecular systems in a wide range of energies. The specifics of solving the problem of interaction of an x-ray photon with a multiatomic system requires the use of a single-center approach to the calculation of the electronic States of molecules. The main disadvantage of this approach is a decrease in the accuracy of the calculation of spectroscopic quantities with limited consideration of the terms of the single-center decomposition of the molecular orbital. The paper studies the effect of accounting for higher harmonics of single-center molecular orbital decomposition on the calculation of the energy characteristics of molecular systems. The analysis of the parameters of the single-center decomposition of the functions of the nuclear ligand, depending on its charge. The criteria for inclusion of higher harmonics of single-center decomposition of atomic ligand functions in the molecular orbital are determined. The calculation of energy characteristics is performed on the example of diatomic molecules HF, LiF and BF. The selected series of molecules makes it possible to study the behavior of higher harmonics of the single-center decomposition of the molecular orbital depending on the growth of the atomic ligand charge.

Keywords: molecular orbital, single-center decomposition, higher harmonics, a nuclear ligand, the energy of the electronic state of a diatomic molecule

Existing methods for assessing the plasticity of soils are labour-intensive, and yield the results of low quality. Due to the importance of this parameter for determining the strength of road beds when designing the construction of railways and highways, the development of new efficient methods for its reliable determination is of great importance. In this paper, we propose a method for solving this problem based on the correlation of mechanical and electrical properties of cohesive soils by the example of soil-forming minerals of montmorillonite and kaolinite

Keywords: layered aluminum silicates, soil plasticity, plastic and liquid limits, absorption, swelling, electrical measurements, correlation of mechanical and electrical properties

Investigation of the interaction of electromagnetic radiation with molecular systems gives most of the information about their structure and properties. Interpretation of experimental data is directly determined by the knowledge of the structure of energy levels and its change in the transition of these systems to an excited state. A key task of the methods for calculating the molecular orbitals of excited states is to accurately describe the emerging vacancies of the molecular core, leading to radial relaxation of the electron density. A method is proposed for an exact description of the electron density of a molecular system near its nuclei, which provides solutions to the problem of slow convergence of molecular orbitals in a single-center representation. The implementation of the computational procedure is examined using the example of a diatomic hydrogen fluoride molecule. The energy characteristics of the ground and ionized states of the molecule are estimated

Keywords: single-center method, molecular orbital, excited state, ionized state, deep shell

The paper presents an overview of the existing calculation schemes and the technique for obtaining the angular parts of the matrix elements of the spectroscopic quantities operators with the discussion of cases of complex electron configurations containing nonequivalent electrons. Using the example of a configuration with four unfilled electronic shells, the high efficiency of the technique for constructing wave functions of arbitrary electronic configurations is shown, based on a combination of Slater's determinant approach and the procedure for sequential coupling of orbital and spin moments on the basis of the Clebsch-Gordan coefficients in the LS coupling approximation.

Keywords: Slater determinant, Clebsch-Gordan coefficient, orbital angular momentum, spin moment, 3j-symbol, coefficients of fractional parentage, LS-coupling

This work presents the results of investigation of one of the most widespread specimens of layered silicates minerals group - montmorillonite, that are the part of the natural dispersion of bentonite from Millerovo minefield via density functional theory (DFT) methods. The hygroscopic moistness of monoions forms of smectite group layered silicates is studied experimentally; these layered silicates are the most active components that significantly determine the properties of the dispersion as a whole. The correlation between hygroscopicity and theoretical values of inter-packet distances is established in studied samples by calculating total energies with optimization of the crystal structure.

Keywords: layered silicates, exchangeable cations, density functional theory, hygroscopicity, montmorillonite

The paper represents the results of theoretical study of molecules behavior of polar aprotonic solvent dimethyl sulphoxide on basal surfaces and in interpackage space of kaolinite. Spectral and energetic regularities of chemical bond formation are studied. Intercalation of DMSO molecules into interpackage space of kaolinite results in the shift of valence vibrations Si-O into high-frequency zone. It also results in vibration suppression of hydroxyl clusters of gibbsite layer. It proves the appearance of strong hydrogen bond between the molecules of polar aprotonic dissolvent and hydroxyl and siloxane kaolinite surfaces. The paper reveals that adsorption of DMSO molecules decreases the surface energy of kaolinite and enables its organophilicity.

Keywords: "layered aluminosilicates dimethyl sulfoxide, density functional theory, intercalation, hydroxyl surface siloxane surface kaolinite"

The paper studies the possibility of interaction of acrylamide with aliphatic di-, tri-, tetra- and pentaamines using quantum chemical ab initio modeling. The interest to the preparation of these compounds can only increase since they may serve as feedstock for the production of other useful materials which may find adequate application. The choice of reaction conditions depends on the thermodynamic principles of the process, and for that reason, the paper determines thermodynamic parameters and the logarithms of the equilibrium constants of acrylamide reaction with aliphatic amines in ratio of 1:1 and 2:1 in the gas phase by quantum-chemical method based on density functional theory using a hybrid exchange-correlation of B3LYP functions in the basis of 3 -21G* within 273 ÷ 450 K temperature range and pressure of 0.1 MPa. These calculations served as a base for defining the conditions that must be followed when developing the technology for these compounds, and it was shown that the reaction of their synthesis with high probability of acrylamide - amine reactants ratio of 2:1 should be conducted under relatively mild conditions. Theoretical calculations comply with the experiment, because the interaction of acrylamide with amines at various ratios of reagents and temperatures within 325 ÷ 330 K leads predominantly to the transformation at acrylamide-amine 2:1 reagent ratio, as evidenced by the number of reactive reagents, and frequency analysis of FT-IR, NMR 1H and 13C spectra.  Thus, the possibilities of mathematical modeling allow determining the highest probability of spontaneity for a particular reaction, using the method of computer simulation by changing the process temperature (within the model) without performing any technological experiments.
       

Keywords: Acrylamide, aliphatic amines, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepenta-amine, thermodynamic parameters, Gibbs free energy, isobaric-isothermal potential, equilibrium constant.

The article depicts test results of ballastless track system roadbed stressed state. In-situ tests of roadbed vertical stresses were held considering rolling stock type and speed. Roadbed vertical stress distribution dependence was carried out.

Keywords: Roadbed, ballastless track system, RHEDA 2000, vertical stress damping, stress distribution

This paper outlines the implementation of computer model of second-order visual mechanisms that are specific to spatial contrast modulations, and represents the results of testing the model. Computer simulation is based on "Filter-Rectify-Filter" model with some important additions. The inhibitory parts of receptive field of simulated mechanism are non-selective to orientation and spatial frequency of texture elements. Texture modulated by orientation or spatial frequency does not reduce flank inhibition and does not activate the mechanism. Unmodulated texture  also does not cause activation of the filter because the flanking inhibition will be equal to or exceed the excitation. However, increasing the contrast in the center and reduction it on the flanks leads to the activation of the second order mechanism.

Keywords: Second order visual mechanisms, image filtering, texture, spatial modulation, computer simulation

The paper studies the possibility of quantitative processing of the GPR data for determining the dielectric permittivity and conductivity of a medium (soil samples). Experimental studies are made using radargrams of soil samples with specified values of moisture and conductivity. New methods of quantitative processing of radargrams are proposed in this work to determine the dielectric permittivity and conductivity of soils. The methods were successfully tested on various sections of Russian railways net.

Keywords: layered road profiling, GPR, soil moisture, soil layers profiling, soil conductivity

This work deals with the study of atomic and electronic structure of kaolinite samples (Glukhovtsy deposit) and montmorillonite (Millerovsky deposit) by density functional theory. The applicability of existing exchange-correlation potential in the local density approximation (LDA) and the generalized gradient approximation (GGA) is analised for an adequate description of the physical properties of layered aluminosilicate. An experimental and theoretical study of the IR spectra of minerals, as well as the identification of the most intense absorption bands, performed in the approximation of DFT using the exchange-correlation potential PW91. The analysis of the band structure of these minerals, which showed that these compounds are direct-gap insulators.

Keywords: DFT, clay, clay minerals, phyllosilicates, atomic and electronic structure, crystalline systems, IR spectrum band strukutra, the electron density

This work deals with the integrated study of the composition and structural characteristics of the rock-forming minerals in Millerovsky bentonite clay. The qualitative and quantitative analysis of the clay samples is made by X-ray diffraction , X-ray photoelectron spectroscopy and thermal analysis . The morphological and microstructural features of minerals are investigated by scanning electron microscopy. The application of the method of direct theoretical calculation of the diffraction patterns is showm to determine the crystal-chemical parameters of the studied minerals. The results are aimed at explaining a number of physical and chemical properties of layered aluminosilicate.

Keywords: clays, clay minerals, layered silicates, x-ray diffraction, crystalline systems

Information about authors of issue №4 (2013)

Keywords: authors

The paper is devoted to developing an approach to solving the problem of structure identification of layered minerals of the kaolinite group by the Rietveld method. The calculations of the intensity of the diffracted X-ray radiation are performed for the koalinit samples obtained from different fields. Qualitative agreement between calculated and experimental results has managed the solution of the identification problem for the kaolinite unit cell Glukhovtsy deposit. The obtained results indicate the possibility of identifying the features of the crystal structure of layered minerals by direct calculation of diffraction patterns.

Keywords: layered minerals, crystal structure, group of koalinit, diffractogram, X-rays, Voigt function, phase composition

  The work is devoted to the development of an intelligent system for monitoring high railway embankment, which allows to analyze its condition and make early solutions to manage the safety of vehicles. The main features of the system and its difference from known analogs is taking into account the dynamic effects of vehicles on a high embankment at different climatic conditions. This paper describes the main stages of building the monitoring system, which includes: selection of objects for monitoring, computer modeling of the interaction of the rolling stock and a high embankment, the algorithms required for the development of management decisions. 

Keywords: high embankments, risk assessment, destruction, monitoring, computer modeling, intelligent system.