Effect of the carbon atom coordination on the thermoactivated motion of the carbon-bonded trichloromethyl group

The reorientational motion of the trichloromethyl group depending on the environment of the carbon atom is considered based on the chlorine-35 nuclear quadrupole resonance (NQR) data. The study is performed for CCl₃ groups bonded to tri- and tetracoordinated carbon atoms in the crystalline compounds CCl₃CCl=NR (R = CH₂C₆H₅ and CCl₃CCl₃) and CCl₃CXClN=CClC₆H₄NO_2-n (X = H and Cl).₃₅Cl NQR studies of thermoactivated motion in 70 solid trichloromethyl-containing compounds are summarized. The ranges of activation energies of CCl₃ reorientations at tri- and tetracoordinated carbon atoms were determined to be 10-50 and 30-90 kJ/mole, respectively, the activation energy being markedly greater in the latter case. CCl₃ reorientations may be completely frozen by the bulky substituents which may be present along with CCl₃ in the tetracoordinated carbon bonds. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 737-746, July-August, 2000     

Optimal recovery of functionals based on inaccurate data

Translated from Matematicheskie Zametki, Vol. 50, No. 6, pp. 85–93, December, 1991.     

Computing lattice sums for calculating the elastic moduli of bcc metals via cluster decomposition

The complete potential energy of a crystal $E\left( {\vec r_{ik} } \right)$ is presented in the form of an expansion in irreducible interactions in clusters containing pairs, triplets, and quadruplets of atoms, situated on A2 lattice sites. The full set of invariants $\left\{ {I_j \left( {\vec r_{ik} } \right)} \right\}$ , on which $\left\{ {I_j \left( {\vec r_{ik} } \right)} \right\}$ can depend is found. Vectors $\vec r_{ik}$ are presented in the form of an expansion of the base of a Brave lattice. This allows us to present $I_j \left( {\vec r_{ik} } \right)$ in the form of integers (lattice sums) multiplied by τ ^m , where τ is half of an elementary cell rib, and m = const is determined by the model. The sum of the Lenard-Jones potential and the potentials of tri- and tetra-atomic interactions was chosen as the model potential. Within this model, elastic moduli of the second and third order were calculated for crystals with A2-type structure.     

Inequalities for derivatives of functions analytical in a strip

This work was supported by the Russian Foundation for Fundamental Research, Grant No. 93-01-00237, and by the International Scientific Foundation, Grant No. MP 1000.     

Quantum yield of radical-recombination luminescence in phosphors based on ZnS and ZnO

The quantum yield of radical-recombination luminescence (RRL) of certain phosphors based on ZnS and ZnO was determined by a calorimetric method. The low yield and its temperature dependence are related to the surface character of RRL excitation and to the catalytic properties of the solid surface.In conclusion we express our gratitude to E. M. Golovchanskii for valuable advice in the construction of the calorimeter.