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.     

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.     

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.     

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.     

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.     

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。     

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.     

New Data on the Isomorphism in Eudialyte-Group Minerals. IV: Modular Structure of Titanosilicate with Replacement of Na by Mn in the Alluaivite Module

Crystallography Reports - A new modular eudialyte-group mineral—titanosilicate—from the Lovozero massif has been investigated using X-ray diffraction. The trigonal-cell parameters are...     

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...     

Electron Beam Induced Changes of the Real Structure of Semiconductors

The formation of irradiation defects produced in a high voltage electron microscope (HVEM) has been studied in Ge and other semiconductor crystals in dependence on various thermal treatments and on covering of the specimen surface. It has been concluded that the defect formation depends — besides general features known for pure metals — also on the state of electrically neutral impurities. Besides, various interactions between dislocations and irradiation defects were observed.     

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 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.     

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).     

Neutronographical investigations of the age hardening behaviour on Iron — Manganese — Nickel alloys

Age hardenable martensitic Iron—Manganese—Nickel alloys were neutronographically investigated in order to explain the age hardening effect occurring during the heat treatment. The formation of coherent precipitations of an ordering phase within the matrix proved to be the reason for the occurring hardness increase.     

Calculation of the Suspension Volumes of MSMPR Cascade Crystallizers

A new algorithm for the design of cascade crystallizers with and without pure solution removal for the individual crystallizers has been described. The algorithm enables the calculation of active suspension volumes and mean retention times, as well as mean size of product crystals and kinetic quantities for the individual stages for the both variants: — presumption of the mean product sizes in each stage, or — presumption of the mean retention times in each stage. Results have been shown and discussed for a two stage cascade of KCl-vacuum crystallizers as example.     

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.     

Optical Properties of Pb-Doped Bi2Te3 Single Crystals

The reflectance and the transmittance spectra in the IR region were measured on Pb-doped Bi₂Te₃ single crystal samples grown by a modified Bridgman technique. The plasma resonance frequency, the optical relaxation time, and the high-frequency permittivity were determined by fitting the Drude-Zener formulas to the reflectance spectra. It was found that Pb impurities in Bi₂Te₃ behave as acceptors. A part of incorporated Pb atoms behaves as electrically inactive. This effect is explained as due to the fact that electrically active Pb-atoms form substitutional defects, Pb′_Bi, and the others form inactive two-dimensional defects — seven-layer lamellae Te—Bi—Te—Pb—Te—Bi—Te. The transmittance spectra were used for the determination of the dependence of the absorption coefficient K on the energy of incident photons. The optical width of the energy gap increases with increasing Pb content. The values of the exponent α from the relation of K ∼ λ^α for the long-wavelength absorption edge range within the interval of 1.6 to 2.8, i.e. the dominant scattering mechanism of free current carriers in Pb-doped Bi₂Te₃ crystals is the scattering by acoustic phonons. By comparison of the effect of doping atoms of the IV.B group of the periodic table on the concentration of holes in Bi₂Te₃ crystal lattice was concluded that the tendency to form substitutional defects Me′_Bi (Me = Ge, Sn, Pb) in these crystals increases from Ge to Pb, whereas the tendency to the formation of seven-layer lamellae Te—Bi—Te—Me—Te—Bi—Te decreases.     

Switching of SBN crystals: Comparison with the model case (DTGS)

It is shown that a number of specific features of the electric-field induced polarization reversal and transition to the single-domain state observed in ferroelectric crystals of SBN-0.61 and DTGS (the model object)— delayed or incomplete transition to the single-domain state in strong fields, hysteresis loop degradation, and time dependence and the memory effect of the residual domain density—are due to the pinning of forward motion (intergrowth) of dynamic domains with charged inclined walls in the absence of lateral motion.