The article presents a crystal-chemical description of the second occurrence of the P21/n modification of sampleite, NaCaCu5(PO4)4Cl·5H2O, discovered at the Kester tin deposit. The formation of this mineral is genetically associated with low-temperature oxidation processes of primary copper, zinc, and tin sulfides, as well as with the formation of later Cu- and Zn-phosphates such as batagayite, epifanovite, and sergeysmirnovite. The positions of hydrogen atoms in the structure of sampleite were calculated using the density functional theory method. To assess the reliability of the theoretical calculations, a comparison between the actual and theoretical IR spectra was conducted. Sampleite formed during the hydrothermal alteration stage of Sn, Cu, and Zn sulfide minerals and coexisted with epifanovite, NaCaCu5(PO4)4[AsO2(OH)2]·7H2O. Epifanovite is undoubtedly a later mineral but has a lower structural complexity (IG, total) of 474.24 bits/cell, compared to sampleite, which has a complexity of 933.32 bits/cell.

Despite the Ni(II) α-diimine based ethylene polymerization catalysts were discovered almost 30 years ago, the mechanism of the ethylene polymerization over these catalysts still remains the subject of the numerous investigations. A significant progress in understanding the nature and role of the nickel compounds formed in real catalyst systems was made over the past 5–7 years. In present publication we summarized and analyzed the data on the nature and role of Ni(II) and Ni(I) species in the catalyst process.

We study the thermoelectric and galvanomagnetic properties of cobalt monosilicide (CoSi) and its solid solutions with FeSi and NiSi. Recent CoSi band structure calculations, confirmed by ARPES measurements, revealed several differences of the electronic structure from the previous standard two-band model for semi-metallic compounds. The discovered features of the CoSi band structure require modifications of previously used models for description of material transport properties. We investigate the temperature dependences of the Seebeck coefficient, electrical resistivity, and Hall coefficient in the temperature range from 100 to 800 K for CoSi and for its solid solutions with FeSi and NiSi. The ab initio calculation of the band structure and transport coefficient were carried out using the Quantum Espresso software package. The results of the study showed that the main features of the thermoelectric and galvanomagnetic properties of CoSi and its solid solutions with FeSi and NiSi at high temperatures can be adequately described using the ab initio calculated band structure, taking into account the energy dependence of the relaxation time.

The thermoelectric properties of thin Cr0.33Si0.67 films in amorphous and crystalline states, as well as at different annealing stages in the temperature range 100–900 K have been studied. The crystallization of amorphous films at a temperature of ~550 K is accompanied by an increase in the resistivity and thermoelectric power. Amorphous films crystallize with the formation of CrSi2 nanocrystals with an average grain size of 10–20 nm. The increase in resistivity is due to the appearance of a crystalline phase and the formation of interphase boundaries between the crystalline and amorphous phases. The scattering of charge carriers at interphase boundaries is selective, which leads to the appearance of an additional contribution to the thermopower.

Thermoelectric properties of cobalt monosilicide CoSi and (Co1 –xMxSi, M = Fe, Ni) alloys are studied. Alloy compositions with an iron content of up to 10 at % and nickel content of up to 5 at % are examined. The thermoelectric power and electrical resistivity are measured at temperatures in the range 100–800 K. Recent calculations of the band structure of cobalt monosilicide have revealed a number of significant differences from the standard semi-metallic model with the energy overlap of parabolic bands for electrons and holes. This requires the modification of previously employed models to describe the transport properties. The possibility of theoretical description of the experimental temperature and concentration dependences of the thermoelectric power and electrical resistivity with the use of different models for description of the electronic spectrum is analyzed.

The samples of cobalt monosilicide CoSi and its alloys with the substitution of iron or nickel for cobalt (Co$_1-x$M$_x$Si, M=Fe, Ni) were studied. The investigation were made for alloy compositions with iron content up to 10 at. % and nickel up to 5 at. %. The thermopower and electrical resistivity were measured in the temperature range of 100 – 800 K. Recent calculations of the cobalt monosilicide band structure revealed a number of essential differences from the standard semimetallic model with energy overlap of parabolic bands for electrons and holes. This raises the question on the effect of the new band structure features on the theoretical interpretation of experimental properties of the compound. We analyze the possibility of theoretical interpretation of temperature and concentration dependences of the thermopower and electrical resistivity using different models of the electron spectrum.

AbstractIn this work, previously undetected intermediates of several practically promising catalyst systems for ethylene polymerization and trimerization are discussed. In particular, the activation of ethylene polymerization catalysts (1) LNiCl2 (L = 2,4,6-trimethyl- (N-5,6,7-trihydroquinolin-8-ylidene)phenylamine) with AlEt2Cl and AlMe2Cl, (2) activation of bis(imino)pyridine vanadium(III) chloride L1VIIICl3 (L1 = 2,6-(ArN=CMe)2C5H3N, Ar = 2,6-iPr2C6H3; 2,6-Me2C6H3; 2,4,6-Me3C6H2; 3,5- F2C6H3) with AlMe3/[Ph3C]+[B(C6F5)]4¯ and MAO, and (3) selective ethylene trimerization catalyst (FI)TiCl3 (FI = phenoxyimine ligand with an additional aryl-OCH3 donor) with MAO have been assessed by NMR and EPR spectroscopy. The nature of ion-pair intermediates – the closest precursors of the propagating species – has been established, and the major catalyst deactivation pathways are discussed.