Growth and study of single crystals of (Na,K)NbO<Subscript>3</Subscript> solid solutions

(Na, K)NbO₃ crystals with a perovskite structure and a KNbO₃ content up to 40 mol % were grown from flux with the use of the solvent NaBO₂. The dielectric measurements of the crystals grown revealed phase transitions that had never been observed before in ceramic samples.     

A procedure for including the “crystal effect” in NQR for the example of (Cl<Subscript>3</Subscript>C)<Subscript>3</Subscript>SiCl

The ³⁵Cl NQR frequencies of (Cl₃C)₃SiCl at 77 K are interrelated with the inverse spin-lattice relaxation times. This interrelation is in the general form described by a hyperbola equation. It is shown that the “crystal effect” can be resolved into long-and short-range environment contributions, and the ³⁵Cl NQR frequency for the C-Cl bonds can be extrapolated to the gaseous state.     

A quantum-chemical study of regioselectivity of indolization of some unsymmetrical ketone phenylhydrazones

The heat of formation (H _f) of unsymmetrical ketone phenylhydrazones and their enehydrazine tautomers was calculated by the semi-empirical quantum-chemical AM1 method. It is concluded that from H _f values it is possible to judge the regioselectivity of indolization of unsymmetrical ketone phenylhydrazones.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 220–221, January, 1993.     

Determination of the purity,melting point and heat of melting of cyclic polyethers

Conclusions Differential scanning calorimeter was used to determine the thermal stability, purity, melting point, and heat of melting of benzo-15-crown-5, dibenzo-18-crown-6, and dibenzo-24-crown-8. These crown ethers have relatively high heats of melting.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 691–692, March, 1986.     

Some properties of the operators of potential theory and their application to the investigation of the basic equation of electrostatics and magnetostatics

Some new properties are proved for the operatorB ^* of the direct value of the potential of a double layer on a closed surfaceS=?ω, in particular the existence inH ^1/2(S) of a basis of eigenfunctions. On the basis of these properties it is proved that the vector integral equation $$\alpha {\rm M}(x) + \nabla \int\limits_\Omega {M(y)} \nabla _y |x - y|dy = H(x), \alpha \geqslant 0,\Omega \subset R^3 ,$$ which is encountered in classical problems of electro- and magnetostatics, is equivalent to the well-known scalar equation with operatorB ^*. The properties of the operator on the left-hand side and of the solutions of the vector equation are investigated.     

Spectral properties of operators of the theory of harmonic potential

We classify the points of the spectrum of the operatorsB andB ^* of the theory of harmonic potential on a smooth closed surfaceS ³. These operators give the direct value onS of the normal derivative of the simple layer potential and the double layer potential. We show that zero can belong to the point spectrum of both operators inL ₂ (S). We prove that the half-interval [–2, 2) is densely filled by spectrum points of the operators for a varying surface; this is a generalization of the classical result of Plemelj. We obtain a series of new spectral properties of the operatorsB andB ^* on ellipsoidal surfaces.Translated fromMatematicheskie Zametki, Vol. 59, No. 1, pp. 3–11, January, 1996.This research was partially supported by the Russian Foundation for Basic Research.     

Paths for the formation of dioxin-type xenobiotics: Quantum-chemical treatment 1. Formation of polychlorobiphenylenes from polychlorobenzenes

The heats of formation of polychloroarynes (PCA's) from polychlorobenzenes (PCB's) have been calculated by the AMI method as a function of the composition and structure of the PCB's according to a two-step scheme including deprotonation with the formation of carbanions (PCCA's, H₁) and dechlorination to PCA's (H₂). The influence of the solvent on H₁ and H₂ has been evaluated in the framework of the solvaton model. It has been shown that the value of H₁ decreases as the number of C1 atoms in the PCB is increased, while H₂ increases along the same series due to the increase in the relative stability of the PCCA as the number of C1 atoms is increased. Although the dimerization of PCA's with the formation of polychlorobiphenylenes (PCBP's) is forbidden by orbital symmetry rules, calculations of fragments of the potential-energy surface have shown that this reaction takes place with an energy barrier amounting to about 1 kcal/mole.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Institute of Organic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 350–355, February, 1992.     

Dielectric dispersion in semiconducting ferromagnetic glass ceramic

Two regions of frequency dispersion of capacitance and conductivity have been discovered in the semiconducting glass ceramics BaTiO₃ and KNbO₃ which have a positive temperature resistance coefficient (PTRC). The low-frequency region (10²–10³ Hz) of dispersion is associated with the existence of barrier layers at the electrodes and the high-frequency region (beginning in the region 10⁵–10⁶ Hz), with the existence of barrier layers at grain boundaries. The frequencies f_m at which maxima of tan corresponding to both dispersion regions diminish in the temperature range of PTRC whereas in the higher region of PTRC they again increase with a rise in temperature. The anomalous temperature dependence of f_m is explained on the basis of the assumption that charge carriers in the barrier layers act as relaxation oscillators and the variations in the barrier heights are described by the Heywang model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 76–81, September, 1978.