Home – Home – Jornals – 2009 number 4

Characteristics of geology, petrology, and geochemistry of the Zijinshan massif were studied in the eastern part of the Ordos basin. Geochemical analysis shows that the massif is characterized by high alkali, relatively high Fe, and low Mg and Ca contents. The rocks are undersaturated in SiO₂, rich in REE (with no Eu anomaly) and belong to the alkaline-peralkaline series. The geologic history of the Zijinshan massif consists of several stages of magmatism. The obtained isotope-geochronological (U-Pb SHRIMP) data show that the magmatic activity climaxed in the interval 150-110 Ma, while the age of 16 zircon grains fitted a narrower interval, 132-125 Ma, i.e., the Early Cretaceous. The younger age corresponds to the middle and late stages of the evolution of the Ordos basin and agrees with a large Early Cretaceous tectonothermal event in North China. This event led to the large-scale uplift of the eastern flank of the Ordos basin, rise of the Lüliang asthenosphere, and to the formation of a large west-sloping monocline. The U-Pb SHRIMP studies have also revealed magmatic zircons of Carboniferous-Permian age, which evidences the multistage character of the thermal process.

The state of the art of the problem of mantle melt transport through the upper mantle beneath spreading zones is reviewed. The geochemical data and physical properties of the mantle constraining the melt migration processes are considered. The review concentrates on the ways of mantle magma transport and mechanisms of the localization of diffuse intergranular porous melt percolation into the channel flow. The hypothesis of the reaction of migrating mantle magmas with wall peridotites and the formation of replacive dunites as a result of this process are discussed. We examine the publications on the field, theoretical, and geochemical studies of the reactive melt migration and its role in the dunite formation in the mantle sections of the ophiolites. Alternative models of the dunite origin in the mantle are also tested. The results of experimental studies of the melt/peridotite interaction are presented.

The geochemical composition of metavolcanics (metabasalts and metaandesites) of the Tunka terrane is considered. They are differently enriched in incompatible elements relative to N-MORB. The geochemical features of the basalts (LILE and LREE enrichment, Zr and Hf negative anomalies) point to the suprasubductional nature of synsedimentary volcanism; at the same time, the rocks lack negative Nb, Ta, and Ti anomalies. Comparison of the Tunka metavolcanics with those of modern geodynamic settings shows their analogy to back-arc basin basalts.

The northern part of the West Siberian geosyneclise is characterized by a thick sedimentary cover and widespread Triassic sedimentary and volcanosedimentary rocks and Paleozoic platform structures. New targets have been recognized in the basement and deeply buried horizons of the geosyneclise cover. Reservoirs might be found in the following formations: Paleozoic cover deposits, weathering crusts, zones of Paleozoic rock deconsolidation, Triassic sedimentary and volcanosedimentary deposits, buried structures in the lower part of the cover, Lower and Middle Jurassic basal layers, pinch-outs of Jurassic horizons, Upper Jurassic bituminous shales and cavernous carbonates. Exploration of these potential structures will change the structure of the existing resource base toward the long-term replenishment of hydrocarbon resources and a stable rate of production replacement.

Neocomian reservoirs in the Mesozoic sedimentary cover of West Siberia have a complex geological structure. Their wedge-like (clinoform) geometry, with abrupt thickness changes and facies diversity (continental, shoreface, and pelagic deposits), causes difficulty in correlation between drilling- and seismics-based sand formations and clay caps. East-wedging (west-dipping) clinoforms consisting of interbedded clay and sand have the greatest reservoir potential in the West Siberian basin. Prediction of new oil and gas plays and their reservoir potential assessment require regional reconstructions in addition to local contour maps of individual zones and fields. However, the simulation technology which has been applied for years to Jurassic regional reservoirs is not fully applicable to the Neocomian clinoform sequences. Therefore we have adapted it correspondingly and suggest new tools to make due regard for the clinoform reservoir structure. The new approach has been tested through computing several structure and thickness contour maps of clinoform sequences for three largest regional Neocomian reservoirs (sub-Sarman, sub-Pim, and sub-Alymka) in northern and arctic West Siberia.

It has been suggested that regional array MTS data be processed with an algorithm based on the nonlocal response of laterally heterogeneous subsurface to an arbitrary electromagnetic excitation. The algorithm is tested with synthetic models which show that the inversion quality can be improved by accumulation of information through repeated measurements, at either changing or fixed array configurations. Besides the array configuration, the inversion quality depends on the selected size of the survey area. The choice of the area size defines the inversion conditions in terms of choice between the magnetic and electric mode for correlation of electromagnetic potentials. The algorithm has been applied to data acquired during the BEAR Project in the Fennoscandian shield. Preliminary results indicate a spatial correlation between conductivity minimums and Moho depth maximums. The apparent resistivity maps obtained with the suggested algorithm highlight the boundaries between the Lapland-Kola, Karelia, and Svecofennia tectonic provinces.

The tectonic framework of China includes major and smaller-scale units that differ in age and in style of tectonomagmatic activity, the latter being related to the thermal history of the lithosphere. Heat flow in the area varies from 25 to 150 mW/m² or higher, with an average of 58±11 mW/m². It is high in active faults, rifts, and other structures of extension (or sometimes compression) subject to heating from rising lithospheric and mantle plumes. The current thermal activity in the region is controlled by the Pacific subduction beneath Eurasia in eastern China and mainly by the lateral strain and rotation of the Ordos block associated with the India-Eurasia interaction in central and western China.

A method of nanostructuring of silicon-on-insulator (SOI) layers on the basis of gas etching in XeF₂ or SF₆:CFCl₃ is developed for the purpose of obtaining SOI nanowire structures. SOI nanowire transistors (SOI NWTs) with free channels, used as sensors in electron detectors, are fabricated and tested. The results of experiments show that the method used to fabricate nanowires requires no hightemperature operations for elimination of defects after nanostructuring of SOI layers. The sensitivity of SOI NWTs to test molecules of bovine serum albumin is 10⁻¹⁵ mole/liter, which is one of the best results for nanowire biosensors.

Chiral metamaterials of the terahertz range are formed by means of rolling of strained nanofilms. Structural elements of these metamaterials are metal-semiconductor microhelices. Resonant optical activity of new metamaterials in the terahertz range is demonstrated. Arrays of model wire helices are formed and tested in the microwave range.

Molecular beam epitaxial growth of HgCdTe solid solutions on silicon substrates of 76.2 mm diameter was studied. Conditions for producing HgCdTe/Si(310) heterostructures for the spectral range of 3-5 μm which are suitable for fabricating high-quality devices were determined. A 4× 288 photodetector was fabricated by hybrid assembly of an array photosensitive element with a multiplexer. Results on the sensitivity and stability of this photodetector to thermal cycling are given.

Current-voltage characteristics of IR photodiodes and distributions of charge carriers in n⁺-n⁻-p-structures based on vacancy p-doped Hg_1−xCd_xTe films with x = 0.22 are examined. Threedimensional numerical modeling of the distribution of charge carriers and current-voltage characteristics during photodiode annealing is performed. The calculations predict that large tunnel currents in diodes after implantation can result from an elevated (more than 10¹⁵ cm⁻³) concentration of donors in the n⁻-layer, which enhances tunneling by decreasing the thickness of the space charged region of the n-p-junction, and also from a small (less than 3 μm) depth of the p-n-junction.

The photomagnetic effect and photoconductivity in a magnetic field are studied at a liquid nitrogen temperature for the Voigt geometry on p-HgCdTe films with graded-gap boundary regions where the content of cadmium (x) is increased above its mole fraction in the central area of the structure with a uniform distribution of x. A case with dominating Shockley-Read recombination is considered. It is demonstrated on the basis of experimental data that the film structure in studying these effects can be replaced by the central area with an identical value of x, by introducing effective velocities of surface recombination and surface generation of excess charge carriers on the interfaces between the central area and the graded-gap regions.

A combined theoretical and experimental analysis of the crystalline phase fraction in nanocrystalline films grown by low-energy plasma-enhanced chemical vapor deposition is presented. The effect of the key parameters, such as temperature, silane flux, and hydrogen dilution ratio, is analyzed. An atomic-scale Monte Carlo model is developed, where the crystallization probability depends on the local environment of the nanocrystalline film. Good agreement is found between the experiments and theory, despite the use of a single fitting parameter.

The self-organization of germanium nanoislands on the surface of calcium fluoride was studied using atomic-force microscopy and reflection electron diffraction. A Ge/CaF₂/Si(111) structure was grown by molecular beam epitaxy. The surface of the calcium fluoride film was modified by submonolayer carbon coverage to stimulate the formation of germanium nanoislands. The arameters of an array of nanoislands were found to depend on the coverage.

A model is proposed to predict the critical parameters (shape, size, element composition) of nanoislands for dislocation nucleation. The onset of plastic relaxation of three-dimensional islands formed during heteroepitaxy in the Stranski-Krastanov mode are considered theoretically for the Ge/Si(100) heterosystem as an example. The study is based on a combination of numerical and analytical approaches to the calculation of strains in three-dimensional island containing a dislocation. It is confirmed that dislocation nucleation in three-dimensional SiGe islands is not limited by the kinetic barrier.

The parameters of a structure consisting of a doped GaAs channel and an AlGaAs buffer located between the substrate and the channel are optimized using the Synopsys Sentaurus TCAD simulator. It is shown that the use of this buffer increases the breakdown voltage and power of the transistor compared to the basic structure transistor without an AlGaAs buffer. It is also shown that the transistor breakdown voltage is most greatly affected by the buffer composition (the fraction of aluminum in the Al_xGa_1−xAs) solid solution and, that the maximum breakdown voltage is obtained for a buffer containing no less than 18 % aluminum.

Nanowhisker formation on substrates activated by catalyst drops is studied by Monte Carlo simulation. Dependences of the whisker growth rate on diameter are investigated for various growth modes. The influence of deposition conditions on whisker morphology is examined. It is shown that straight thin whiskers of uniform thickness can be obtained only using a catalyst having a large contact angle with the whisker material. In such a physicochemical system, variation of growth conditions can result in nanotube formation. An atomic mechanism for the formation of a hollow whisker is proposed. Ranges of model growth conditions suitable for the growth of nanowhiskers and nanotubes are determined.

It is shown that the blocking layer of the flash memory element based on silicon nitride has an optimal value of the dielectric constant, which allows the maximum memory window in the write/erase regime to be reached.

This paper reports the results of experimental studies and calculations of components of a model system for detection and imaging in the terahertz range, including a free-electron laser and devices for laser radiation diagnostics, film shields with absorbing coatings for intermediate thermal imaging, and prototype sensitive elements based on PbSnTe:In films.

A vertical-cavity surface-emitting laser on the basis of Al_xGa_1−xAs solid solutions is developed. The laser displays stable single-mode operation at a wavelength of 795 nm, which offers the prospects of its application in miniature chip-scale atomic clocks.

Monte Carlo simulations of atomic processes on the surface of silicon nanochannel membranes during molecular-beam epitaxy and subsequent thermal oxidation are performed. It is demonstrated that silicon deposition on Si(001) wafers with 1-100 nm cylindrical pores results in constriction of channel inlets. The rates of reduction of the nanochannel diameter are estimated as functions of the wafer temperature, silicon deposition rate, and initial nanochannel diameter. Optimal conditions of silicon deposition on nanochannel membranes are determined: the wafer temperature of 250-450 °C and silicon flux intensity of 10⁻² to 10 monolayers (ML) per second. Under these conditions, the rate of reduction of the nanochannel inlet diameter is 0.13-0.15 nm/ML, which allows membrane channel modifications over a wide range down to several nanometers. Simulations of nanochannel membrane oxidation in an oxygen flux shows that precise reduction of nanochannel inlet diameters down to complete sealing of the channel due to oxide growth is only possible for small diameters of the initial pores. For channels with large lateral sizes, the effect of reduction of the channel inlet diameter due to oxidation is insignificant. Oxidation of pores enhances their stability to subsequent high-temperature treatment.

This paper gives experimental results of quantum key distribution on a fiber-optic setup at a telecom wavelength of 1555 nm. A self-compensated two-channel optical circuit is used. Quantum key distribution was performed by coding the phase states of single photons radiated by a pulsed semiconductor laser in two alternative nonorthogonal bases. Specially developed single photon counters based on InGaAs:InP avalanche photodiodes were employed as high-sensitivity photodetectors. The results of investigation of the quantum efficiency, probability of afterpulses, and noise level for various operating modes of the detectors at temperatures from −40 to −60 °C are given. A key distribution rate of 450 bit/s was obtained for a single-mode fiber-optic quantum communication channel between the receiver and sender 25 km long at a laser pulse clock frequency of 5 MHz and an average number of photons per pulse of about 0.2. For the achieved photodetector characteristics, the average number of errors in the quantum key did not exceed 3.7 %.

Using MM2 molcular mechanics simulation and MNDO/PM3 semiempirical methods we show that the most probable mechanism of surface modification of alkyl-doped silicon dioxide layers in plasma is the interaction with СН₃ groups. Detachment of the hydrogen atom causes a change in the character of Si-O-Si bonding, which results in an increase in the number of Si-O-Si groups with an angle in a range of 144° to 146°. Subsequent treatment in ammonia plasma leads to pore sealing through the formation of -CH-Si-O-Si-O-Si-O-Si- chains. The mechanism proposed provides a good explanation to FTIR experimental spectra and to changes in the reactivity of porous layers after treatment in helium plasma.

The vaporization enthalpy of polyatomic alcohols with different structures under normal conditions is calculated using a modified Randič method. The vaporization enthalpy of polyatomic alcohols is shown to largely depend on the number of hydrogen bonds formed by alcohols.

Using a hybrid B3LYP density functional method with the 6-31G(d) basis set and the Gaussian-98 program, the geometrical parameters of macrocyclic complexes of Co(II), Ni(II) and Cu(II) with NNSS-coordination of donor centers of the chelate ligand, formed due to template processes in M(II)-hydrozinomethane thiohydrazide-acetone systems, are calculated. Coordinates of atoms, selected bond lengths and angles, and dihedral angles in complexes with MN₂S₂ metal-chelate site are given. It is noted that for all considered M(II) ions the additional six-membered metal cycle, formed because of template stitching, is turned at a considerable angle to two five-membered cycles, and this cycle itself is not planar either.

Heteropoly acid (HPA) H₈(PW₁₁TiO₃₉)₂O·xH₂O (I) is synthesized by three different ways and studied by chemical analysis, potentiometric titration, mass-spectrometry, IR, ³¹P, ¹⁸³W, and ¹⁷O NMR spectroscopy, thermogravimetry, and transmission electron microscopy. Anion I consists of two subparticles of the Keggin structure bridged by Ti-O-Ti. The dimeric anion exists in HPA aqueous solutions at [I] > 0.02 M. At рН > 0.6 it splits to a [PW₁₁TiO₄₀]^5- monomer stable up to рН ~ 6. When heated (150-400)°C, I splits into H₃PW₁₂O₄₀ and, apparently, H₃PW₁₀Ti₂O₃₈ without phase separation. Thermolysis products are soluble and when dissolved in water turn again into I. Complete decomposition of I to oxides occurs at ~450°C.

The molecular dynamics method is used to simulate the structure of liquid chlorobenzene, ortho-chlorotoluene, and their mixtures with concentrations of 0.03 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, and 0.95 ppm chlorobenzene. Radial angular distribution functions (RADFs) were found for the distances between benzene ring planes and the angle between them in pure components and solutions. The data obtained from RADFs indicate that in the nearest environment of molecules the parallel orientation of benzene rings is the dominant configuration, while the fraction of perpendicular contacts is relatively small. In a concentration range of 0.03 ppm, 0.05 ppm, and 0.95 ppm chlorobenzene, conglomerates form with structural characteristics close to those of the dissolved substance. At a concentration of 0.1 ppm chlorobenzene, solute molecules start to agglomerate. In a concentration range from 0.15 ppm to 0.9 ppm chlorobenzene, both agglomerates and conglomerates of the same size are present in the mixture. The radial distribution functions of chlorine-chlorine distances calculated in pure components and mixtures indicate the presence of chlorine aggregates. The results obtained are compared with molecular light scattering data.

Structural thermodynamic parameters of aqueous solutions of hexamethylphosphorotriamide are calculated. They are discussed together with previously obtained data on aqueous solutions of disubstituted amides of carboxylic acids. The specific and non-specific components of the total energy of intermolecular interactions are determined. The boundaries of concentration regions with different structural organizations of solutions are found, and the preferential solvation parameters of solution components are estimated.

XRD is used to study the structures of inclusion compounds of diterpenoid 15-ene-steviol with chloroform and 16-S-dihydrosteviol with chloroform and ethyl acetate. In all three cases, the guest-host ratio is 1:2; by means of a branched system of hydrogen bonds, diterpenoid molecules form a three-dimensional associate with helical voids, in which solvent molecules are located. Crystals of all three complexes are isostructural, the ethyl acetate molecule being localized in the corresponding inclusion compound, while solvent molecules are disordered in complexes with chloroform.

Every crystallographic group has finite sets of conical sections (for planar groups) and second order surfaces (for spatial groups). A geometrical method has been suggested on this basis for modeling and studying the cooperative mobility of atoms in symmetric systems. The method was demonstrated for a 21-atomic cluster (point group T-23). It suggests the construction of a variety of regular point systems, interpreted as sequential stages of the cooperative motion of the atoms of the 21-atomic cluster with preserved inner coordinates (bond lengths and angles) in a narrow range of values.

UV spectra of 2-substituted-1-(p-vinylphenyl)cyclopropanes are studied. Based on spectral data, different substituents (-Х) are characterized with respect to their effect on the system of conjugated bonds in the molecule . The cyclopropane ring is found to be a part of the conjugated system of the whole molecule.

The nature of epitaxial intergrowth of black (β) and red (α) modifications of zinc diphosphide is studied. The intergrowth of single crystals is shown to be caused by that the atoms-analogs form almost identical structural motifs in both structures. The black modification grows on the (001) plane of the red one so that its b axis is parallel to the (110) plane of α-ZnP₂.

We have synthesized (±)-diphenyl-4′-chlorophenyl-[(2-hydroxy-1,1-dimethylethyl)amino]methylphospho-nate and studied it by X-ray diffraction.

A principle to design the multi-parameter potentials of hydrogen bonding is proposed and developed. Based on fluctuation theory, they provide the description of temperature evolution of the shape of OH vibrational spectra of liquid water molecules. Approximate solutions expressing the ν_OH frequency and hydrogen bond energy E through the hydrogen bond length and bending (R_O…O, ϕ_H-O…О) and the pair of angles (ϕ_Н-О…О,
χ_-О…О) adjacent to it are found numerically. By their means, spectra are calculated fairly close to experiment in a temperature range up to 200°C. The expressions proposed can be used to quantitatively analyze the networks of hydrogen bonds in computer models of water obtained by Monte-Carlo or molecular dynamics methods.

By means of IR absorption spectra, low temperature ¹Н and ¹⁵N NMR spectra, and quantum chemical calculations we study the structure of complexes with hydrogen bond of molecular and ionic character formed by nitrogen-containing compounds able to be both proton donors and acceptors simultaneously and the interaction specificity in them. Spectroscopic, steric, and thermodynamic characteristics of diphenyltriazene, 3,5-dimethylpyrazole, and diphenylformamidine homoassociates and heterocomplexes of these compounds with carboxylic acids and various proton donating molecules are obtained. Quantum chemical calculations of the structure of complexes and vibrational frequencies in IR spectra are made in the harmonic approximation and with regard to anharmonicity corrections. Calculations taking into account anharmonicity of vibrations are shown to produce the results closest to the experimental data.

The effects of photoirradiation on the conformation state of 4-(4′-dimethylaminostyryl)pyridine N-oxide was studied by spectral (EAS, ¹Н NMR, IR) and thermochemical methods. Trans→cis isomerization was found to proceed in 4-(4′-dimethylaminostyryl)pyridine N-oxide irradiated with light (λ ≤ 400 nm) in chloroform. The conversion of the trans form of 4-(4′-dimethylaminostyryl)pyridine N-oxide to the cis form depends on the time and intensity of irradiation. Maximum conversion was achieved when a photostationary mixture formed with a ratio of components trans:cis = 40:60. Further irradiation of the solutions of 4-(4′-dimethylaminostyryl)pyridine N-oxide in chloroform led to salification with HCl formed during the decomposition of CHCl₃.

Based on the data of the Cambridge Structural Databank, we analyzed the conformations of 139 4-X-C₆H₄-C₆H₄-4′-Y molecules (X, Y = H, F, Cl, Br, I, CH₃, OH, COOH, NH₂, NO₂, CN) and intermolecular contacts formed by these molecules in 95 homo- and heteromolecular crystals. As would be expected, the percent of planar and almost planar molecules (the angle between the planes of the phenyl fragments (ϕ) is 0-5°) in the group was higher (37%) than in biphenyl containing any substituents in the 3,3′,4,4′,5,5′-positions (26%). The percent of almost planar molecules increased considerably when X = OH (48% among molecules having at least one OH group), while equal substituents (X = Y) did not lead to a substantial increase in the relative content of conformers with ϕ in this range. In the given group of crystal structures, the specific intermolecular contacts (hydrogen bonds, Hal…Hal and Hal…N≡C contacts, etc.) often led to the formation of infinite molecular chains or their fragments (trimers and dimers). The structures containing molecules with an NH₂ group typically formed layered (2D) and framework (3D) H associates.

For H bonds stabilized by π-conjugation in carbonylated 1,4-dihydropyridines, an analysis of the structural data of the Cambridge Structural Databank showed that the hydrogen bond was an essential condition for π-conjugation. It was found that π-delocalization possibly correlated with the bioactivity of drugs that were calcium antagonists. In the presence of two carbonyl groups, hydrogen bonds in crystal are predominantly formed by the carbonyl group that is anti-periplanar to the 1,4-dihydropyridine ring.

Systematization of the available literature data on С-F…π, F…Н, and F…F interactions, namely, statistical studies of the geometry of the corresponding contacts were carried out using the Cambridge Structural Database (CSD) and theoretical quantum-chemical estimations of their energies. The most typical supramolecular motifs (finite or infinite) involving the F atom were revealed based on recent X-ray studies of a few dozens of fluoroarenes carried out at the Novosibirsk Institute of Organic Chemistry. Our recent data were summarized. To assess the role of the above interactions, we used topological analysis of electron density distribution in terms of Bader's QTAIM theory. Our DFT/PBE/3z quantum-chemical calculations of the interaction energies of molecular pairs in diazafluorene crystals formed by С-F…π, C-F…Н, and F…F nonvalent short contacts are presented.

The properties of intercalated compounds of graphite fluoride with highly volatile polar guest components were studied by DTA, XRPA, and IR spectroscopy. The role of guest−host and host−host intermolecular interactions in the formation of layered inclusion compounds based on polymer matrices with different degrees of fluorination is shown.