Theoretical temperature-electric field phase diagram for deuterated thiourea SC(ND2)2

A theoretical temperature-electric field phase diagram is constructed for thiourea SC(ND₂)₂ using a phenomenological approach based on the representation of the thermodynamic potentials for all phases. The theoretical diagram is compared with the experimental diagram. Fiz. Tverd. Tela (St. Petersburg) 39, 1282–1286 (July 1997)     

Fluorides of ruthenium and chromium: Theoretical studies

The electronic and structural characteristics of CrF₅, CrF₄, RuF₅ and RuF₄ were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF₅ in D_3h, triplet for CrF₄ in T_d, quadruplet for RuF₅ in C_4v and quintuplet for RuF₄ in D_4h symmetry.     

The structure of the nematic-isotropic interface in polymer systems

The structure of the nematic-isotropic interfacial layer is studied theoretically for systems formed by rod-like and persistent macromolecules. It is shown that the width of interfacial layer is normally of the order of the straight part of a molecule. This allows us to use the approach which describes intermolecular interactions phenomenologically (i.e. it allows us to consider all interactions), at the same time this approach describes molecular flexibility microscopically (i.e. it allows us to study the effects of flexibility correctly). It was found, that non-monotonic gradient profiles in the surface layer of the order parameter or of the concentration of molecules as a function of the coordinate perpendicular to the interface are possible. For example, a thin layer with abnormal ordering of molecules along the surface may exist near the interface for some systems.     

Kinetics and mechanism of oxidation of indigo carmine by hypohalites

Kinetics of oxidation of indigo carmine (IC) by sodium hypohalites, NaOX (X ? Cl or Br), in alkaline buffer of pH 9–11 has been studied spectrophotometrically at λ = 610 nm. The experimental rate law obtained is ?d[IC]/dt = k[OX^?][IC][OH^?]^x where x <1. Variation of ionic strength or dielectric constant of the medium had no effect on the reaction rate while the addition of halide ions slightly retarded the rate. A most plausible mechanism proposed on the basis of experimental results involves the formation of isatin sulphonate which undergoes further oxidation to anthranilate. Activation parameters have been evaluated.     

Step-strain deformations for viscoelastic fluids: Formulation of a strain-coupling constitutive equation

An integral constitutive equation which includes strain-coupling effects is proposed. The constitutive equation is more general than the K-BKZ equation, and it is shown that this equation can explain various important aspects of double-step stress-relaxation data.     

Intercalated smectic-A structures in a new class of laterally branched substances

X-ray, DSC and optical studies of a new class of substances with aromatic rings in the lateral branches are reported. The thermal behaviour of the substances is discussed. The X-ray measurements lead to a structural model of the SA phases consisting of layer structures with intercalating molecules.