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  • 1
    Electronic Resource
    Electronic Resource
    Distinction of space groups (I23 and I213) and (I222 and I212121) using coherent convergent-beam electron diffraction (2000)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 359-369 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Convergent-beam electron diffraction (CBED) is well known as a powerful tool to determine space groups of crystals. However, it cannot distinguish several sets of space groups. It is shown theoretically that the coherent CBED method can distinguish between space groups (I23 and I213) and between (I222 and I212121), which belong to indistinguishable sets. It is demonstrated by computer simulations that the relative arrangement of 2-fold-rotation and 21-screw axes can be distinguished by examining the relative phases of specific reflections through the interference fringes of coherent CBED patterns. This fact implies that these space groups can be distinguished by the coherent CBED method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767300004001
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  • 2
    Electronic Resource
    Electronic Resource
    Vacancy–strain coupling in ordered TiO (1978)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 556-561 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of the partially ordered phase of TiO has been examined with a single crystal. While the space group is that first determined from powder X-ray diffraction and electron diffraction by Watanabe, Castle, Jostons & Malin [Acta Cryst. (1967). 23, 307-313], (B2/m), the average structure is somewhat different. There are waves of Ti and O ion vacancies every third (100) plane in the [010] direction of the monoclinic structure. The amplitude of the wave is twice as large for the Ti ion vacancies as for the O ion vacancies. There is no appreciable concentration of interstitial Ti ions in either the ordered phase or the disordered (cubic) phase. The ordering temperature Tc is 1026 (2)°C. The monoclinic angle is directly proportional to the square of the order parameter associated with vacancy ordering. A mean-field theory is developed that includes vacancy-vacancy and vacancy-electron interactions, and vacancy-strain coupling. This theory explains the main features of the order-disorder transition in this material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739478001199
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  • 3
    Electronic Resource
    Electronic Resource
    Distinction between space groups having principal rotation and screw axes, which are combined with twofold rotation axes, using the coherent convergent-beam electron diffraction method (2001)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 219-230 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: 23 sets of space groups remain indistinguishable by the convergent-beam electron diffraction (CBED) method. Recently, Tsuda, Saitoh, Terauchi, Tanaka & Goodman [Acta Cryst. (2000), A56, 359–369] demonstrated that the coherent CBED method can distinguish two space-group pairs (I23, I213) and (I222, I212121) by observing the relative arrangements of 2-fold-rotation and 21-screw axes. The other ten space-group sets, which are composed of principal rotation and screw axes and other 2-fold-rotation axes such as P321 and P3121 (P3221), are shown to be distinguishable using the coherent CBED method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767300014896
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  • 4
    Electronic Resource
    Electronic Resource
    A convolution method for the calculation of bond scattering factors (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 185-186 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The X-ray scattering factor of bond electrons in a diatomic molecule is calculated from Fourier transforms of atomic wave functions, by the use of the convolution theory. For the hydrogen molecule, it is shown that the contribution of bond electrons is large for the scattering vector in the direction of the molecular axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000354
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  • 5
    Electronic Resource
    Electronic Resource
    X-ray diffuse scattering from pentaerythritol (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 678-679 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The X-ray diffuse scattering from pentaerythritol is measured at various temperatures. By taking account of five intermolecular force parameters, the dispersion relations are calculated and compared with the observed data. It is found that the interaction between the oxygen atoms connected by the hydrogen bond is stronger and more sensitive to temperature than other interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471001451
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  • 6
    Electronic Resource
    Electronic Resource
    Short-range ordering of vacancies in TiO at 1323 K (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 646-652 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The diffuse X-ray scattering from a single crystal of disordered TiO was measured at 1323 K in a volume in reciprocal space. The short-range order parameters between vacancies and cations and anions were determined by Williams's [(1972). Report ORNL-5140. Oak Ridge National Laboratory, Tennessee] least-squares procedure for fitting the total intensity to contributions from this local order and up to quadratic terms in the atomic displacements. Computer simulations with the short-range order coefficients reveal that the local atomic arrangements are similar to those in the low temperature phase. The relationship between this local order and the electronic conductivity is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739479001509
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  • 7
    Electronic Resource
    Electronic Resource
    Polarized XAFS study of high-temperature phases of NaNbO3 (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 833-835 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Temperature dependence of the Nb displacement relative to the center of oxygen octahedron in NaNbO3 has been studied by polarized Nb K XAFS. Spectra were measured at two orientations of a single crystalline sample. Room temperature EXAFS data are in a good agreement with earlier X-ray diffraction data: Nb antiferroelectric displacements were found to be orthogonal to the b axis. Analysis of the temperature dependent EXAFS data didn't reveal any abrupt changes of Nb-O distances in the phase transition points. In all high-temperature paraelectric phases Nb appeared to be displaced to the off-center positions. Displacements, orthogonal to b axis, remained almost constant, while displacement along b axis gradually increased with temperature, so that in the cubic phase the displacements along all axes became equal. This shows, that disorder plays an important role in the high temperature phases. The above results are supported also by the analysis of the pre-edge structure, - the integral intensity of the pre-edge peak was temperature-independent when the polarization vector of the X-rays was orthogonal to b axis and gradually increased with temperature when the polarization was parallel to b.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500018069
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  • 8
    Electronic Resource
    Electronic Resource
    Polarized XAFS study of the atomic displacements and phase transitions in KNbO3 (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 367-369 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599001351
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  • 9
    Electronic Resource
    Electronic Resource
    EXAFS studies of KBr1−x(NO2)x mixed crystals (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 486-488 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599000928
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  • 10
    Electronic Resource
    Electronic Resource
    EXAFS study of phase transitions in KIO3 (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 803-805 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The iodine K-edge EXAFS study of KIO3$ was performed to clarify local structural changes on the successive phase transitions. The pair-distribution function of three oxygen atoms in an oxygen octahedron is almost independent on temperature like a covalent bond, whereas that of the other three is gradually reduced with increasing temperature like an ionic bond. The result indicates that iodine and oxygen atoms exist as an IO3− molecule in a pseudo-perovskite-type structure. The anomalous behavior in the Debye-Waller factor for the latter pair-distribution function appears around 50 K, which is associated with the orientational glass transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090904950001832X
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