Structural and mineralogical school of N.V. Belov at Moscow State University: New data on silicates obtained at the Department of Crystallography and Crystal Chemistry

The new data on the tetrahedral complexes that have been revealed in the structures of natural silicates at the Department of Crystallography and Crystal Chemistry of the Faculty of Geology, Moscow State University (MSU), in the last years are analyzed. Some new minerals and structural types are considered. Possible mineral transformations occurring deep in the earth are described.     

Chromatographic methods and techniques used in studies of coals, their progenitors and coal-derived materials

The use of chromatography in studies of coals, their progenitors and coal-related products was reviewed. The specificity of the coal structure was discussed. The use of extraction in preparing study samples was discussed paying special attention to the occurrence of undesirable phenomena such as aggregation of coal derivate molecules, resulting from the formation of their dimers and trimers, and degradation of polar solvents at temperatures above 350 °C. The following ways of fractionating samples of coal materials were considered: thermal, solvent, column with the use of preparative size exclusive chromatography and preparative thin layer chromatography as well as membrane separation. The use of chromatography coupled with experimental techniques such as mass spectrometry, infrared spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and pyrolysis was analysed.     

Refinement of composition and structure of holtite I

A new version of the structural formulas of holtite I, (Al_0.61Ta_0.25□)(Al_0.96□)₂(Al_0.96□)₂ × (Al_0.90□)₂(Si_2.49Sb_0.35As_0.13)O_13.46(O_0.48OH_0.52)(BO₃), is reported. The main changes in this formula are related to the incorporation of arsenic atoms in (Sb,As)O₃ pyramides into the structure.     

Absorption frequencies and intensities in the vibrational spectra of perfluoroparaffins. C2F6 and C3F8 molecules

Journal of Applied Spectroscopy -     

Study of the structure of low-alkali potassium-germanate glasses by the Raman scattering method

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 5, pp. 827–833, May, 1989.     

Crystal structures of potassium-exchanged forms of catapleiite and hilairite

The crystal structures of potassium-exchanged forms of catapleiite and hilairite of the compositions (K_0.49Ca_0.42Na_0.26)ZrSi₃O₉ · 2[(H₂O)_0.8(H₃O)_0.2] and K_0.51ZrSi₃O₉ · 3[(H₂O)_0.5K_0.27(H₃O)_0.23], respectively, were studied by X-ray diffraction and IR spectroscopy. Both structures retain the heteropolyhedral frameworks of the parent minerals formed by Zr octahedra and Si tetrahedra. The K cations occupy different positions in these minerals. In K-exchanged catapleiite, K cations are located only in the position occupied by Na in the structure of the parent mineral. In the K-exchanged form of hilairite, K cations are not only involved in the Na position but also partially occupy the H₂O position.