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 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
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