ISSN:0232-1300    

DOI:10.1002/crat.2170310420

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170310421

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractChromium‐doped Sb2Te3single crystals were prepared from elements of semiconductor purity using a modified Bridgman method. The samples of these crystals were characterized by means of X‐ray diffraction analysis, measurements of the reflectivity in the plasma resonance frequency range ωp, of the Hall constantRHand electrical conductivity σ. It was found that the incorporation of Cr atoms into the Sb2Te3crystal lattice reduces the volume of the unit cell, whereas the values of ωpandRH(i.e. the concentration of holes) remain unaltered and the values of σ decrease with increasing chromium content. This effect is qualitatively explained by an interaction of incorporated Cr atoms with antisite defects of Sb2Te3crystal lattice. The In (RHσ) vs. InTdependences show that the dominant mechanism of scattering of free charge carriers in the studied crystals is the scattering by acoustic phonons; the presence of chromium atoms increases the scattering rate by ionized im

ISSN:0232-1300    

DOI:10.1002/crat.2170310402

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe reaction rate of Li intercalation into Bi2Se3−xSxsingle crystals (x = 0, 0.025 and 0.05) increases with an increasing sulfur content in the crystals. This effect has been explained qualitatively by a change in the bond polarity in the Bi2Se3due to the substitution of selenium atoms by sulfur atoms. This substitution results in a change in the electron density distribution and thus also in the width of the van der Waals gap between the structural layers, responsible for the course of intercalation. This explanation is supported by a quantum‐chemical calculation of the charges on the atoms of the Bi2Se3−xSxlattice manifesting and increase in the negative charge on Se atoms with an increasing value

ISSN:0232-1300    

DOI:10.1002/crat.2170310403

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractSemicarbazide cadmium chloride (SCCC) is an organometallic nonlinear optical crystal. Preparation and crystal growth of SCCC have been studied, thermal and IR spectral properties of the crystal are characterized. Investigations of the molecular and crystal structures show that there is a large charge‐transfer bridge in the molecule, and that the crystal has a distorted polyhedrally‐coordinated structure. The relations between the structures and NLO effects of complex crystals have been discussed, and optimization of structures of organometallic NLO crystals are sugges

ISSN:0232-1300    

DOI:10.1002/crat.2170310404

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract2‐(3,4,5‐trimethoxyphenyl)‐benzothiazole, C16H15NO3S was obtained by condensation of 2‐aminobenzenethiol with 3,4,5‐trimethoxybenzoldehyde. The structure of the title compound was indicated by IR,1H‐NMR, UV spectra and confirmed by an X‐ray analysis. In the molecule the trimethoxyphenyl and benzothiazole groups are connected by a CC bond of 1.478(6) Å. The trimethoxyphenyl except a methoxy group and the benzothiazole group are nearly planar. The dihedral angle between these p

ISSN:0232-1300    

DOI:10.1002/crat.2170310405

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractRoom‐temperature phases of nickel hexamina perchlorate (NHP) and nickel hexaamina tetrafluorborate (NHT) were analysed by means of X‐ray powder diffractometry. Both compounds crystallize in the cubic system (Fm3m space group) with cell parameters:a= 11.4689 Å for NHP anda= 11.2692 Å for NHT structure, respectively. The crystal structures of these compounds were refined using Rietveld m

ISSN:0232-1300    

DOI:10.1002/crat.2170310406

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractAlpha‐quinacridone crystallizes in the triclinic space group P1withZ= 2,a= 14.934 ± 0.064 Å,b= 3.622 ± 0.004 Å,c= 12.935 ± 0.040 Å; α = 91.39 ± 0.28°, β = 107.13 ± 0.02°, γ = 92.84 ± 0.24°. The molecules are connected by hydrogen bonds more far from linearity (≈145°) than gamma‐quinacridone 162°). Together with π‐π bonds, building molecular stacks along the short axisb= 3.622 Å, both types of bonds run through the whole lattice. Molecules within the hydrophobic planes exhibit orientational disorder. Transitions between gamma‐ and alpha‐quinacridone has been discussed: all inversion centers are retained, only the vectors of bravais lattice and the angles of molecules in the stacks are changed. The calculated pattern of alpha‐quinacridone is compared with the experimental one by means of overlay‐ and difference plots. – The transition character of the alpha‐quinacridone is stressed by generation of a combined pattern of 50% alpha‐ and 50% gamma‐quinacridone, cal

ISSN:0232-1300    

DOI:10.1002/crat.2170310407

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDark‐green multimetal compound crystal [Cu(bipy)2(Cr2O7)]· 2 H2O was obtained from aqueous solution of Cu(NO3)2, K2Cr2O7and bipyridine. The crystal structure was determined by X‐ray crystallography: triclinic P1,a= 7.716(3) Å,b= 9.656(3) Å,c= 15.517(5)Å, α = 77.41(3)°, β = 81.04(3)°, γ = 82.33(3)°,Z= 2. In this compound, two chromium atoms and a copper atom are linked by two oxo bridges (Cu(II)OCr(VI)OCr(VI)). The copper coordination polyhedron corresponds to a five‐coordinated disto

ISSN:0232-1300    

DOI:10.1002/crat.2170310408

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe structure of the cubic high temperature phase of Ca8[Al12O24] (CrO4)2, CACr, has been determined at 700 K by Rietveld analysis of neutron powder diffraction data. The structure is discussed with respect of those of its homologues. The phase transitions of the title compound have been investigated by means of synchrotron x‐ray powder diffraction and differential thermo analysis. High precision lattice parameters have been determined in the temperature range between 350 and 750 K. Three phase transitions occurring at 610 K, 453 K, and 432 K could be verified. Observed anomalies in the lattice parameters versus temperature might indicate a yet unknown phase transition at about 555 K. This is supported by results of differential thermo analysi

ISSN:0232-1300    

DOI:10.1002/crat.2170310409

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY