133 Cs NMR was employed to study the structural characteristics and properties of perovskites at the atomic level. CsBi x Pb 1− x Br 3 perovskites doped with Bi at concentrations of 0.0059, 0.0072, and 0.0120 were studied. The importance of high-quality materials for applications in optics and photonics was noted. 133 Cs NMR showed high sensitivity for studying these concentrations of Bi, which affect the stability of perovskites and their dynamic parameters.

Рассмотрены легированные соединения халькопирита. Приведены результаты изучения спектральных параметров методом ядерного магнитного резонанса 63,65 Cu в локальном поле, а также методом электронного парамагнитного резонанса в интервале температур 15-300 K. Наблюдаемое уширение резонансных линий спектров ядерного магнитного резонанса и обнаружение парамагнитного сигнала в образце при температуре 15 K свидетельствуют о появлении антиструктурных дефектов. Быстрое изменение формы линии спектра электронного парамагнитного резонанса в интервале температур 100-130 K связывается со структурно-фазовым переходом. Ключевые слова: термоэлектрики, соединения халькопирита, антиструктурные дефекты.

Doped chalcopyrite compounds are considered. The results of studying the spectral parameters by the 63,65Cu NMR method in a local field, as well as by the EPR method in the temperature range 15-300 K are presented. The observed broadening of the resonance lines of the NMR spectra and the detection of a paramagnetic signal in the sample at a temperature of 15 K indicate the appearance of anti-structural defects. The rapid change in the shape of the EPR spectrum line, in the temperature range 100-130 K, is associated with the structural-phase transition. Keywords: thermoelectrics, chalcopyrite compounds, antisite defects.

THE PURPOSE. Reveal the regularities of turn-to-turn faults influence on to parameters of a three-phase network transformer in the disconnected transformer mode with the supply of control voltages and currents from an external source in the transformer linear operation. METHODS. To achieve the purpose, experimental studies were carried out on the power transformer (Trihal with a voltage of 20 / 0.4 kV) with an artificially created turn-to-turn fault, mathematical modeling and calculations of the three-phase transformer magnetic system parameters. RESULTS. Experimental measurements of the open circuit voltage were performed on the power transformer high voltage side by applying a three-phase positive sequence voltage to the transformer low voltage side. Similar measurements were carried out using a three-phase zero sequence current. The influence of the turn-to-turn fault on the magnetic system of the three-phase transformer with the application of voltages and currents of zero and direct sequences is investigated. A mathematical model of three-phase transformer magnetic system has been developed, which makes it possible to determine the change in the parameters of the transformer windings and to establish the relationship between the primary and secondary voltages and currents in conditions of the occurrence of а turn-to-turn fault. The parameters of the three-phase transformer magnetic system were calculated from the results of experimental measurements. CONCLUSION. An effective method for detecting turn-to-turn faults by measurements with the supply of zero sequence currents is proposed. A simplified model of the three-phase transformer magnetic system has been developed. This model allows us to qualitatively evaluate the changes in the transformer parameters when a turn-to-turn fault occurs. A model of turn-to-turn fault is proposed, which can be used to study the effect of turnto- turn fault on the transformer magnetic system.

63,65 Cu NMR study was carried out on a series of Cu 1–x Pd x FeS 2 compounds (x = 0–0.02) in a local magnetic field at 77 K. The spectra of the samples were taken. Their parameters were determined and the fields in the region of 63,65 Cu nuclei were estimated. Asymmetric broadening of the NMR resonance lines was found along with a smoother decay in the high-frequency region, which may result from an increase in the amount of defects in the crystal lattice of the compound. These can be FeCu 2+ antistructural defects, whose formation is attributed to the generation of the PdS phase in the chalcopyrite matrix with an increase in the nominal Pd content.

A Cu-63,Cu-65 NMR study was carried out on a series of Cu1-xPdxFeS2 compounds (x = 0-0.02) in a local magnetic field at 77 K. The spectra of the samples were taken. Their parameters were determined and the fields in the region of Cu-63,Cu-65 nuclei were estimated. Asymmetric broadening of the NMR resonance lines was found along with a smoother decay in the high-frequency region, which may result from an increase in the amount of defects in the crystal lattice of the compound. These can be FeCu2+ antistructural defects, whose formation is attributed to the generation of the PdS phase in the chalcopyrite matrix with an increase in the nominal Pd content.

Samples of a series of Cu 1–x Pd x FeS 2 (x = 0—0.02) compounds were studied by 63,65 Cu NMR in a local field at a temperature of 77 K. The spectra of the samples were measured, their parameters were determined, and the fields in the region of 63,65 Cu nuclei were estimated. An asymmetric broadening of the resonance NMR lines with a smoother decay in the high-frequency region was found, which may be the result of an increase in the number of defects in the crystal lattice of the compound. Such defects can be Fe Cu 2+ antisite defects, the formation of which is caused by the formation of the PdS phase in the chalcopyrite matrix with an increase in the nominal Pd content.

Thin films of haycockite Cu4Fe5S8 on glass substrates were deposited by flash evaporation technique from powders of this compound. The composition of thin films correspond to the atomic content of Cu, Fe, and S of 24.13, 27.90, and 47.97 at.% with the Cu/Fe and S/(Cu + Fe) atomic ratios of 0.87 and 0.92 respectively, whereas the corresponding theoretical values for this material amount to 0.80 and 0.89. The as-prepared thin films of haycockite consist of a set of separate fractions of approximately identical areas of about 400 - 600 µm2. It can be assumed that this structure evolved during cooling down of thin films since it completely covers the surface of thin films. A small inclusion of a second phase with the chemical composition close to talnakhite Cu9Fe8S16 is also observed. Haycockite Cu4Fe5S8 is found to be a direct gap semiconductor with the energy band gap Eg equal to 1.26 eV as determined using both transmission and surface photovoltage methods.

AbstractThe results of studying natural samples of CuFeS_2 chalcopyrite mineral from hydrothermal ore manifestations of island arcs of the Pacific Ocean by ^63Cu nuclear magnetic resonance (^63Cu NMR) in a local field at room temperature are presented. The asymmetric shape of the detected resonance lines in the ^63Cu NMR spectrum indicates the presence of at least two overlapping lines. The presence of two overlapping central components can be a consequence of the occurrence of regions with different types of structural distortion near the resonant nuclei. These results show that the pulsed ^63Cu NMR method can be an effective method for studying the physical properties of deep-sea polymetallic sulfides of the global ocean.

The results of studying natural samples of CuFeS 2 chalcopyrite mineral from hydrothermal ore manifestations of island arcs of the Pacific Ocean by 63 Cu nuclear magnetic resonance ( 63 Cu NMR) in a local field at room temperature are presented. The asymmetric shape of the detected resonance lines in the 63 Cu NMR spectrum indicates the presence of at least two overlapping lines. The presence of two overlapping central components can be a consequence of the occurrence of regions with different types of structural distortion near the resonant nuclei. These results show that the pulsed 63 Cu NMR method can be an effective method for studying the physical properties of deep-sea polymetallic sulfides of the global ocean.

Представлены результаты исследования природных образцов минерала халькопирита CuFeS2 из массивных океанических сульфидных руд Срединно-Атлантического хребта методом ядерного магнитного резонанса 63Cu (ЯМР 63Cu) в локальном поле при комнатной температуре. Значительная ширина обнаруженных резонансных линий в спектре ЯМР 63Cu прямо свидетельствует о большом распределении локальных магнитных и электрических полей в исследованных образцах халькопирита. Это распределение может быть следствием заметного отклонения состава исследованных образцов халькопирита от стехиометрического. Полученные результаты показывают, что импульсный метод ЯМР 63Cu может быть одним из эффективных методов изучения физических свойств глубоководных полиметаллических сульфидов Мирового океана. DOI: 10.21883/FTP.2017.01.8253

The results of investigating natural samples of chalcopyrite mineral CuFeS2 from massive oceanic sulfide ores of the Mid-Atlantic ridge by the 63Cu nuclear magnetic resonance (NMR 63Cu) in a local field at room temperature are presented. The significant width of the resonance lines found in the 63Cu NMR spectrum directly testifies to a wide distribution of local magnetic and electric fields in the investigated chalcopyrite samples. This distribution can be the consequence of an appreciable deviation of the structure of the investigated chalcopyrite samples from the stoichiometric one. The obtained results show that the pulsed 63Cu NMR can be an efficient method for studying the physical properties of deep-water polymetallic sulfides of the World Ocean.

The resonance \(^{63,65}\)Cu NMR spectra in the internal magnetic field in cubanite CuFe\(_{2}\)S\(_{3}\) and chalcopyrite CuFeS\(_{2}\) were studied experimentally at 77 K. Using a cluster approach, ab initio evaluation of the electric field gradient (EFG) at the nuclei of copper in both compounds was performed. The calculations were carried out by the self-consistent restricted method of Hartree–Fock with open shells (SCF-LCAO-ROHF). The largest clusters for which calculations were made had a formula of Cu\(_{7}\)Fe\(_{14}\)S\(_{29}^\mathrm{n}\) for cubanite and Cu\(_{9}\)Fe\(_{10}\)S\(_{28}^\mathrm{n}\) for chalcopyrite, where n is the cluster charge. The best-fit values of the quadrupole parameters (quadrupole frequency \(\nu _\mathrm{Q}\) and the asymmetry parameter of the EFG tensor \(\eta \))—determined experimentally (\(\nu _\mathrm{Q} \approx \) 7.30 MHz and \(\eta \approx \) 0.82) and by calculation (\(\nu _\mathrm{Q} \approx \) 7.38 MHz and \(\eta \approx \) 0.87)—were obtained for a cluster Cu\(_{7}\)Fe\(_{14}\)S\(_{29}^{10}\) for cubanite. Similarly, the best-fit values of the quadrupole parameters—determined experimentally (\(\nu _\mathrm{Q} \approx \) 1.29 MHz and \(\eta \approx \) 0.34) and by calculation (\(\nu _\mathrm{Q} \approx \) 1.40 MHz and \(\eta \approx \) 0.50)—were obtained for a cluster Cu\(_{9}\)Fe\(_{10}\)S\(_{28}^{-4}\) for chalcopyrite. For these clusters, maps of the electron density distribution in the neighborhood of quadrupole nucleus of copper were built. Based on the analysis of the resulting electron density distribution, it is supposed that the bond in these compounds is not quite covalent. Evaluations of the hyperfine interaction constants were made and maps of the spin density distribution in the neighborhood of quadrupole nucleus of copper were built. The energy level diagram calculated in the high-spin ROHF approximation defined chalcopyrite as a compound with a very narrow LUMO–HOMO gap rather well and is consistent with the notion of this compound as a semiconductor.

The resonance ^63,65 Cu NMR spectra in the internal magnetic field in cubanite CuFe _2 S _3 and chalcopyrite CuFeS _2 were studied experimentally at 77 K. Using a cluster approach, ab initio evaluation of the electric field gradient (EFG) at the nuclei of copper in both compounds was performed. The calculations were carried out by the self-consistent restricted method of Hartree–Fock with open shells (SCF-LCAO-ROHF). The largest clusters for which calculations were made had a formula of Cu _7 Fe _14 S _29^n for cubanite and Cu _9 Fe _10 S _28^n for chalcopyrite, where n is the cluster charge. The best-fit values of the quadrupole parameters (quadrupole frequency ν _Q and the asymmetry parameter of the EFG tensor η )—determined experimentally ( ν _Q≈ 7.30 MHz and η≈ 0.82) and by calculation ( ν _Q≈ 7.38 MHz and η≈ 0.87)—were obtained for a cluster Cu _7 Fe _14 S _29^10 for cubanite. Similarly, the best-fit values of the quadrupole parameters—determined experimentally ( ν _Q≈ 1.29 MHz and η≈ 0.34) and by calculation ( ν _Q≈ 1.40 MHz and η≈ 0.50)—were obtained for a cluster Cu _9 Fe _10 S _28^-4 for chalcopyrite. For these clusters, maps of the electron density distribution in the neighborhood of quadrupole nucleus of copper were built. Based on the analysis of the resulting electron density distribution, it is supposed that the bond in these compounds is not quite covalent. Evaluations of the hyperfine interaction constants were made and maps of the spin density distribution in the neighborhood of quadrupole nucleus of copper were built. The energy level diagram calculated in the high-spin ROHF approximation defined chalcopyrite as a compound with a very narrow LUMO–HOMO gap rather well and is consistent with the notion of this compound as a semiconductor.

Characteristic NMR parameters of 63,65Cu in the local magnetic field of the semiconductor mineral chalcopyrite CuFeS2 were measured in the range 26–77 K. The behavior of the 63,65Cu NMR spectral and relaxation parameters in the local field indicated that a magnetic phase transition related to antiferromagnetic ordering of Cu2+ magnetic moments did not occur at ~50 K in the studied CuFeS2 sample.

We have used pulsed 63,65Cu nuclear quadrupole resonance at room temperature to study the semiconductor compound CuAlO2 with a delafossite crystal structure, and we have determined the quadrupole frequency νQ = 28.12 MHz and the asymmetry parameter η ~ 0, which we used to study the features of the electron density distribution in the vicinity of the quadrupolar nucleus. In order to take into account the influence of correlation effects on the electric field gradient, we carried out ab initio calculations within the density functional theory (DFT) approximation using a set of correlation functionals VWN1RPA, VWN5, PW91LDA, CPW91, and B3LYP1. We mapped the electron density distribution in the vicinity of the quadrupolar copper nucleus for the Cu7Al6o 14 ‐ 1 cluster and we calculated the size of the LUMO–HOMO gap, Δ ~ 3.33 eV. We established the anisotropy of the spatial electron density distribution. Based on analysis of the electron density distribution obtained, we suggest that the bond in CuAlO2 is not purely covalent.

To choose the most efficient method and ore beneficiation flow diagram, it is important to know physical and chemical properties of ore concentrates. The feasibility of application of the 63,65Cu nuclear magnetic resonance (NMR) method in a local field aimed at studying the properties of copper ore concentrates in the copper–iron–sulfur system is demonstrated. 63,65Cu NMR spectrum is measured in a local field for a copper concentrate sample and relaxation parameters (times T1 and T2) are obtained. The spectrum obtained was used to identify a mineral (chalcopyrite) contained in the concentrate. Based on the experimental data, comparative characteristics of natural chalcopyrite and beneficiated copper concentrate are given. The feasibility of application of the NMR method in a local field to explore mineral deposits is analyzed.

NMR spectra of 63,65Cu in an internal magnetic field were studied experimentally. The electric field gradient (EFG) at Cu nuclei in chalcopyrite CuFeS2 was evaluated ab initio by using a cluster approach. Calculations were carried out in the framework of the self-consistent field restricted open-shell Hartree–Fock method (SCF-LCAO-ROHF). The largest cluster for which calculations were carried out had the formula Cu9Fe10S28 n (R ~ 6 Å, 47 atoms), where n is the cluster charge. The best agreement of the quadrupole parameters (quadrupole frequency νQ and EFG tensor asymmetry parameter η) that were determined experimentally (νQ = 1.29 MHz, η = 0.34) and were calculated (νQ = 1.40 MHz, η = 0.50) was obtained for the cluster Cu9Fe10S28 −4. Maps of electron-density distribution in the neighborhood of the Cu quadrupolar nucleus were built for the cluster Cu9Fe10S28 −4. It was suggested based on an analysis of the obtained electron-density distribution that the bond in chalcopyrite is not covalent. The energy-level diagram that was calculated in the ROHF high-spin approximation defined rather well chalcopyrite as a semiconductor with a very narrow LUMO–HOMO gap and was consistent with the notion of chalcopyrite as a gapless semiconductor.