Pyroelectric properties and structural defects of a layered TlInS2 crystal doped with lanthanum

The results of investigations of the pyroelectric current in a layered TlInS₂ crystal doped with lanthanum are presented. A comparative analysis of the obtained results and data of photo-induced current transient spectroscopy has been performed. The revealed features of the contribution from electrically active defects to pyroelectric properties of the crystal have been discussed.     

A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion

Dichalcogenolenes are archetypal redox non-innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2-protected imidazolium salt. This ligand is diamagnetic, which is in contrast to the paramagnetic nature of standard dichalcogenolene monoanions. The new ligand is also redox-active, as demonstrated by isolation of a stable diselenolene radical dianion. The unique electronic properties of the new ligand give rise to unusual coordination chemistry. Thus, preparation of a hexacoordinate aluminum tris(diselenolene) complex and a Lewis acidic aluminate complex with two ligand-centered unpaired electrons was achieved.     

Photovoltaic currents and activity of structural defects in a ferroelectric–semiconductor TlInS<Subscript>2</Subscript>: La single crystal

This paper reports on the results of the investigation of electrically active defects in the crystal structure in a layered ferroelectric–semiconductor TlInS₂: La crystal by photoinduced current transient spectroscopy (PICTS). It has been found that there are states of the crystal that differ in the magnitude of the photoresponse varying within four orders of magnitude, which is interpreted in terms of the differences in states of the domain structure of the crystal. The specific features of the recording of thermal emission from defects in the presence of an additional contribution from the photovoltaic component of the response of the crystal to excitation with light have been discussed.     

Experimental detection of specular reflection of gamma quanta

Scattering of bremsstrahlung electron beam (E _e = 6.25 MeV) collimated with a vertical divergence δ_γ ≈ ±60 μrad and incident on the mercury surface at glancing angles α = −37, −83, and −140 μrad is studied on the 118-m-long path length. The specular reflection effect is detected in the spectral and angular distributions of γ quanta with energies up to 3 MeV. The reflection coefficients vary from 0 to ∼17% depending on the angles of incidence and the γ quanta energy.     

Effect of external fields on the memory effect of the incommensurate phase in the ferroelectric-semiconductor TlGaSe<Subscript>2</Subscript>

The effect of external fields (dc electric field, light illumination) on the memory effect of the incommensurate phase in the ferroelectric-semiconductor TlGaSe₂ is studied using the measured dielectric constant. The results obtained are discussed. It is shown for the first time that the effect of external fields on the anomaly related to the memory effect in TlGaSe₂ can be reduced to the following universal empirical rule: when a sample is held for many hours at a constant temperature T ₀ in the temperature range of the incommensurate phase in a dc electric field, the deflection amplitude in the low-temperature part of the anomaly in the temperature dependence of the relative change in the dielectric constant Δ?/? increases (the deflection in the high-temperature part of the Δ?/? anomaly disappears) as compared to this segment in the dependence obtained during isothermal annealing of this sample at the same temperature without an electric field. The crystal remembers its thermal history at a temperature that is several kelvins higher than T ₀. Light illumination increases the deflection amplitude in the high-temperature part of the Δ?/?(T) anomaly and shifts the temperature at which the crystal remembers its thermal history toward lower temperatures with respect to T ₀.     

Random matrix theory and analysis of nucleus-nucleus collision at high energies

We propose a novel method for analysis of experimental data obtained in relativistic nucleus—nucleus collisions. The method, based on the ideas of random matrix theory, is applied to detect systematic errors that occur in measurements of momentum distributions of emitted particles. The unfolded momentum distribution is well described by the Gaussian orthogonal ensemble of random matrices, when the uncertainty in the momentum distribution is maximal. The method is free from unwanted background contributions. The text was submitted by the authors in English.     

Synthesis of Tetraarylethene Luminogens by C−H Vinylation of Aromatic Compounds with Triazenes

Tetraarylethenes are obtained by acid-induced coupling of vinyl triazenes with aromatic compounds. This new C−H activation route for the synthesis of aggregation-induced emission luminogens is simple, fast, and versatile. It allows the direct grafting of triarylethenyl groups onto a variety of aromatic compounds, including heterocycles, supramolecular hosts, biologically relevant molecules, and commercial polymers.     

Effect of the “negative chemical” pressure on the temperatures of phase transitions in the TlInS<Subscript>2</Subscript> layered crystal

The temperature dependences of the permittivity of TlInS_{2(1 −x)}Se_2x solid solutions have been experimentally investigated in the temperature range including the points of structural phase transitions in the solid solutions. It has been established that the isovalent substitution of selenium for sulfur in the anion sublattice of the TlInS_{2(1 − x)}Se_2x solid solutions shifts the phase transition temperatures T _i and T _c toward the low-temperature range with a simultaneous decrease in the temperature interval of the existence of the incommensurate phase. The T-x phase diagram is constructed for the solid solutions under study and the coordinates are determined for a critical point (of the Lifshitz type) at which the lines T _i (x) and T _c (x) converge in the phase diagram. The pattern of the T-x phase diagram for the TlInS_{2(1 − x)}Se_2x solid solutions has been analyzed within the phenomenological model of a virtual crystal.     

Fractal analysis of time series in oil and gas production

The peculiarities of fractal characteristics’ calculations for time series are described in this article. An algorithm for calculation of fractal dimension is suggested. It has been proved that the suggested method possesses high accuracy and the rapidity of convergence on the limited number of measurements compared to the methods of covering.The criteria of early diagnosis for changes in the condition of hydrodynamic processes, which do not vary by fractal dimension, have been recommended.The presented method is applicable for practical engineering calculations with self-affine, chaotic data, usually with relatively limited number of measurements. It is quite a simple method for calculation of fractal dimension, algorithm can be easily realized and it should be useful for engineers.The applicability of the proposed algorithm for fractal dimension calculation and early diagnosis criteria of qualitative changes in the behaviour of various dynamic systems has been tested both on simulated as well as practical examples of oil and gas production.     

Unusual memory effects in an incommensurate phase of the TlInS2 ferroelectric semiconductor

The experimental data on memory effects in an incommensurate phase are analyzed both in undoped layered TlInS₂ crystals selected from different technological batches and in TlInS₂: La. Various types of unusual memory effect are detected. It is shown that the observed memory effects are due to pinning of the soliton superstructure by a defect density wave in the internal field of the electret state. Original Russian Text ? M.-H. Yu. Seyidov, R.A. Suleymanov, F. Salehli, S.S. Babayev, T.G. Mammadov, A.I. Nadjafov, G.M. Sharifov, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 533–542.