Registration Number
0215U001225,
0112U001280
, R & D reports
Title
Chemical bonding in intermetallics and related compounds: electron density from X-ray diffraction
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Head
Gladyshevskii Roman Evgenovych,
Registration Date
03-02-2015
Organization
Ivan Franko National University of Lviv
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Object of investigation - intermetallic compounds and related classes of inorganic compounds with unique chemical and physical properties, in particular compounds of metal and semimetal elements with modulated and composite structures. Subject of investigation - determination of the crystal structures of compounds with constant or variable compositions based on precise diffraction experiments, including refinements of the coordinates, inharmonic and multipole parameters of the atoms, and synthesis of the experimental electron density; interpretation of the chemical bonding and physical properties. Purpose of the project - a new approach to the description of the atomic structure of inorganic substances in the solid state, which allows representing not only qualitative characteristics, but also quantitative parameters of chemical bonds. The investigation was focused on the establishment of general algorithms expressing the correlation between structural features and the character of chemical bonding in intermetallic and other inorganic compounds. Methods of synthesis and investigation - melting in arc, high-frequency or muffle furnaces, a.c. electrochemical synthesis, annealing in muffle furnaces, single-crystal and powder X-ray diffraction using conventional laboratory equipment or a synchrotron source, neutron diffraction, energy-dispersive X-ray analysis, differential thermal analysis, thermal gravimetry, Raman spectroscopy, infrared spectroscopy, measurements of the electrical resistivity by the standard four-contact method, of heat capacity, magnetic susceptibility, magnetization, Vicker's hardness, quantum-mechanical calculations based on the density functional theory. The crystal structures of 114 inorganic compounds were determined from high-precision diffraction data, and the chemical bonds analyzed. For the modulated structures of LiZn4-x, Eu2Rh1-xGa5, EuPt2Ga2, (Tb0.70Zr0.30)(Al0.17Si0.83), and for the composite structure of Dy0.64{Dy5[Fe2C9]}, quantitative characteristics of the modulation in multi-dimensional space were obtained: modulation vectors, modulation amplitudes of the atomic positional coordinates and site occupancies. Original software was created for the refinement of multipole parameters, using the Hansen-Coppens model for the calculation of the 3D distribution of electron density from X-ray diffraction data and the method of minimization of difference function of experimental structure factors. Parameters of multipole models were refined and sections of deformation and valence electron density were obtained. New software was created for the determination and analysis of detailed patterns of chemical bonding. In order to find the peculiarities of the electron density distribution, a program of laplacian calculations, using 3D fast Fourier transform of the real space of the unit cell on a uniform grid, was written. Quantitative characteristics of the chemical bonding, based on the experimental electron density obtained from X-ray diffraction, were determined for a certain number of compounds, making it possible to draw some conclusions on the principles of chemical bonding in intermetallic compounds. The influence of the nature of components on the crystal structure, chemical bonding and properties of compounds synthesized within the project was analyzed. 700 structure types of inorganic compounds with tetragonal symmetry were systematized according to their crystallographic and crystal-chemical characteristics. Results of the scientific research carried out within the project are included in eight master works, two diploma works, ten bachelor works, two PhD theses, and one tutorial. They have been published in 63 scientific articles (49 in journals included in scientometric databases) and two monographs, and presented at national and international conferences (60 conference abstracts of which 44 at international conferences); one patent of Ukraine was obtained. The results are also used as examples in courses on inorganic chemistry and crystal chemistry for bachelor and master students at the University of Lviv. Some of the results obtained during the project are currently used at the I.M. Frantsevich Institute for Problems of Materials Science (NAS) and G.V. Karpenko Physico-Mechanical Institute (NAS).
Product Description
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Аксельруд Лев Григорович
Горинь Андрій Маркіянович
Заремба Оксана Іванівна
Зелінський Анатолій Вікторович
Луцишин Юрій Ярославович
Сливка Юрій Іванович
Стадник Юрій Володимирович
Токайчук Ярослав Олексійович
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2020-04-02
