The Base of the Computation of Quantitative Changes Running in Technological Processes in the Multicomponent Systems with Mixed Crystals

The three multicomponent systems (KCl—KBr—H₂O, K₂SO₄—(NH₄)₂SO₄—H₂O, KNO₃—NH₄NO₃— H₂O) with mixed crystals in their solid phases have been studied. The isotherms of solubility and the curves of distribution have been mathematically described. The system of equations, which allows to calculate the quantitative changes running in technological processes in the multicomponent systems with mixed crystals has been proposed.     

Study of the effect of crystallization parameters on gaseous inclusions in sapphire ribbons grown by the Stepanov method

Crystallography Reports - The effect of growth parameters on the two main types of gaseous inclusions in sapphire ribbons—bubbles in the crystal bulk and near-surface pores—have been...     

Molecular Dynamics Study of Thymidine Phosphorylase from E. coli in the Apo Form and in Complexes with Substrates

Crystallography Reports - Models of E. coli thymidine phosphorylase in complexes with the substrates — the complex with phosphate and the complex with phosphate and thymidine — were...     

New Data on the Isomorphism in Eudialyte-Group Minerals. III: Modular Structure of K Analog of Centrosymmetric Labyrinthite

Crystallography Reports - The crystal structure of a new modular eudialyte-group mineral from the Khibiny massif—potassium-rich analog of labyrinthite—has been investigated using X-ray...     

The determination of liquidus data in the In-As system

Liquidus data of the In—As system were determined in the temperature range 450–630 °C using a seed dissolution technique. The analytical estimation of the arsenic content in the melt was carried out by coulometric titration. In the investigated region, the plot of In x(1 — x) versus 1/T shows a weak concave curvature with reference to the 1/T axis.     

Investigation of II—IV—V Systems by the Method of Differential Thermal Analysis

It is reported on experiences with the investigation of II—IV—V systems by DTA. Two different arrangements with different sensibility were used. Because of the high volatility of the component V, i.e. phosphorus, samples generally were put in sealed quartz ampoules. Because of the danger of ampoule bursting a special heating procedure was necessary. The results on various II—IV—V systems confirm and precise most of the data of the literature.     

Diophantine laws for nets of the highest symmetries

The theoretical-numerical properties of the square and the hexagonal nets are presented as well as their characteristic triads of integers—the Denis numbers—applicable to the practical X-ray diffraction analysis of single crystals.     

Interfacial stability and grain diameter of the metal phase of directionally solidified Al-Si-type eutectics

The morphology of the solid-liquid interface and the metal phase grain diameter of Al—Si-type eutectics (Al—Si, Ag—Si, Ag—Ge, Zn—Ge) were investigated in the range of a growth rate R = 0.2 … 20 mm/h and of a temperature gradient at the solid-liquid interface G = 2 … 25 K/mm. Three types of interfacial morphologies depending on the G/R ratios were found out. The G/R ratio of the transition from a planar to a nonplanar solid-liquid interface corresponds to the critical G/R|_c ratio, which can be calculated by the criterion of the constitutional undercooling. The grain diameter of the metal phase depends on growth parameters as follows: d_K ∼ R^—rG^—g with r = 0.33 … 0.43 and g = −0.37 … 0.03.     

The Influence of the X-ray Wavelength on the Behaviour of Polar Kossel Reflections

The Kossel effect permits a determination of polar directions in non-centrosymmetrical structures. To identify polar reflections unambiguously, differences — as large as possible — in their fine structures are necessary. These differences considerably depend on both the diffraction geometry and the characteristic X-ray wavelength applied. The reasons of such behaviour are deliberated upon hereinafter and a good harmony achieved of theoretical predictions and experimental findings.     

Study of the complex vibrational spectra of natural mesolite

The vibrational spectra of the natural zeolite, mesolite (locality Akureyri-Island) were measured in the infrared (200—400 cm⁻¹) and the far infrared — FIR (40—400 cm⁻¹) regions: the infrared reflectance (200—1400 cm⁻¹) and Raman scattering (50—3600 cm⁻¹) spectra of the polycrystalline material were also measured. The Schimanouchi GCCC, BGLZ, and LSMA programs were used to calculate the force constants and vibrational frequencies of the Si O, Al O, O H, cation-oxygen, O Si O, O Al O, H O H bonds and libration of H₂O and Si(Al) O Si on the basis of the symmetry coordinates. The KKK-1 program (Petzelt, Kroupa) was used to calculate the dispersion curves of the complex refractive index for both parts of the complex dielectric permittivity in the whole measured wavenumber region. The bands in the spectra were assigned to the vibrations of the individual bonds and structural groups of the mesolite on the basis of theoretical calculations.     

原位ATR-IR光谱实时研究DKDP的结晶过程

采用全反模式的红外(ATR-IR)光谱实时研究了不同氘含量KH_2-xD_xPO₄(DKDP)晶体的结晶过程,其中DKDP溶液氘含量范围为0到99%。通过υ₁(PO₄)和υ₃(PO₄)振动表征了DKDP结晶溶液中(H₂PO₄^-)_1-x(D₂PO₄^-)_x离子基团浓度的变化。υ₁(PO₄)振动强度的变化和υ₃(PO₄)振动宽度的变化说明生长溶液中的(H₂PO₄^-)_1-x(D₂PO₄^-)_x离子浓度随着测试时间延长而不断增大。同时,δ(P—O…H/D—O—P)振动峰的形成说明DKDP晶体的生长基元为(H₂PO₄^-)_n-x(D₂PO₄^-)_x离子团簇。波数在1 448 cm^-1到1 653 cm^-1范围内H—O—H和D—O—D振动强度的变化解释了DKDP晶体在结晶过程中氘含量分布不均的现象。     

Configurations of the zero-birefringence and zero-dichroism lines of electromagnetic waves in weakly anisotropic crystals

Configurations of two types of lines—those of zero birefringence and zero dichroism—drawn by the end of the directional vector of the wave normal over the unit sphere, which correspond to the coincident phase velocities or the absorption coefficients of isonormal electromagentic waves in weakly anisotropic crystals, have been studied analytically. It is shown that under the conditions of weak dielectric anisotropy, even slight changes in anisotropy result in the dramatic deformation of the lines of both types. The corresponding evolution of the configurations with the change of the anisotropy parameters is considered by example of absorptive orthorhombic crystals.     

Density and Ultrasonic Velocity Measurements in Hexyloxybenzylidene Phenylazoaniline

The temperature variation of density and ultrasonic velocity of the liquid crystal hexyloxybenzylidene phenylazoaniline are reported. The density across the smectic A—smectic B transition is more predominant than the other transitions. The density variation with temperature and the calculated thermal expansion coefficients suggest that the transitions isotropic liquid—nematic, nematic—smectic A and smectic A—smectic B are of first order. Anomalous behaviour of ultrasonic velocity is observed across the isotropic liquid—nematic transition and prominent dips in velocity are observed at the nematic—smectic A and smectic A—smectic B transitions. The adiabatic compressibility (β _ad ) Rao number (R _a ) and molar compressibility (B) are estimated using the experimental density and ultrasonic velocity.     

Conformational Analysis of Thermotropic Liquid Crystalline Polyesters

PCILO conformational calculations have been carried out on several model compounds of thermotropic liquid crystalline polyesters [—OC—φ—φ—φ—CO—Os—R—O—] where R = (—CH₂—)₂; (—CHCH₃—)₂; (—CHCH₃—CH₂—). Several conformations corresponding to the trans and gauche states of the C-C single bonds are preferred, the TGT form being of lower energy than the TTT form. The replacement of—CH₂—group by—CH(CH₃) group results in a decrease of the number of the energy minima, an increase in the energy of the molecule in all the preferred conformations, compared to that of the TGT form, a sharpening of the potential energy wells and an increase in the energy barriers. The presence of a methyl group also shifts the aliphatic chain away from the ideal trans and gauche positions.     

Effect of Ultraviolet Irradiation on the Ice Nucleating Ability of AgI—AgCI—CuI System

The effect of ultraviolet radiation on the nucleating behaviour of AgI, AgCI, AgI–AgCI–CuI system in pure water has been discussed. Also the effect of irradiated AgI—AgCI—CuI samples in the presence of chlorides of sodium, potassium, and ammonium as well as sulphates of sodium, ammonium, and magnesium has been reported. The UV exposed samples of AgI and AgCI become darkened and their nucleating activity is found to be greatly reduced as the time of exposure is increased. It is found that the exposure of the AgI—AgCI—CuI samples to ultra-violet radiation does not produce a remarkable effect in nucleation activity, except, the samples becoming dark for longer exposure timings.     

Synthesis and Crystal Structure of NdCaGaO4

The crystal structure of the NdCaGaO₄ compound was investigated by means of X-ray structure analysis (powder diffractometer HZG-4, CuK_α): structure type LaCuO₄, space group Cmca, a = 5.3700(2) Å, b = 12.1058(3) Å, c = 5.3937(2) Å, Z = 4, R_I = 0.126. The shortest interatomic distances are: Nd(Ca)—O — 2.240(14) Å; Ga—O — 1.913(2) Å, O—O — 2.6852(2) Å, Nd(Ca)—Nd(Ca) — 3.442(3) Å, Nd(Ca)—Ga — 3.154(4) Å, Ga—Ga — 3.8056(2) Å. Atoms have the following coordination numbers: Nd(Ca) — 8; Ga — 6; O1 — 14(6); O2 — 9(5).     

The importance of the oxygen ion concentration for oxidic high-temperature solvents

Using e.m.f. measurements we determined relative oxygen ion concentrations of the systems PbO—PbF₂—B₂O₃, PbO—MoO₃—B₂O₃, PbO—Bi₂O₃—V₂O₅, 3 PbO · MoO₃—Fe₂O₃, and 3 PbO · MoO₃—Ga₂O₃. Furthermore the alteration of the relative oxygen ion concentration of pure PbO was observed after stepwise addition of the solvent components PbF₂, B₂O₃ and of the garnet forming oxides Fe₂O₃ and Y₂O₃ giving complete high temperature solutions for the Y₃Fe₅O₁₂ preparation. Applying the Lux' acid-base concept the behaviour of these oxide mixtures is discussed. Combinations which contain weak bases and weak acids allow the adjustment of a desired oxygen ion concentration that is little changed by added oxides for crystal growth. These combinations show favourable properties as solvents for oxidic substances with complicated compositions, e.g. perovskites, garnets, ferrites.     

Penetration depth of tin in float glass

Experimental results on float glass by recent analytical techniques — ESCA, photon emission induced by ion bombardment and ellipsometry — support the conclusion that tin from a metal bath penetrates with relatively high concentration only in the first few nanometers from the surface.     

Low-angle boundaries in germanium

Possible mechanisms of formation of dislocation defects—low-angle boundaries—in germanium single crystals used in optics are considered.     

Electrochemical Emission during Deformation of Titanium Grade 2 Alloy in an Aquatic Medium

Crystallography Reports - The time-dependent component of electrode potential—electrochemical emission (ECE) signal—of polycrystalline titanium Grade 2 alloy during deformation in...