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  • Electronic Resource  (20)
  • 1985-1989  (8)
  • 1975-1979  (11)
  • 1910-1914  (1)
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  • Electronic Resource  (20)
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  • 1
    Electronic Resource
    Electronic Resource
    Electrical conductivity measurements on olivines and pyroxenes under defined thermodynamic activities as a function of temperature and pressure (1979)
    Springer
    Physics and chemistry of minerals 4 (1979), S. 189-197 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Electrical conductivities of Ni2SiO4, Fe2SiO4, and MgSiO3 were measured on synthetic powders in the temperature range 340° to 1,100° C and at pressures up to 20 kbars. For ternary compounds such as olivines and pyroxenes the control of two further variables, like the chemical activities of two components are needed, besides temperature and pressure. The activities of the corresponding binary oxides were controlled by equilibrating the samples with their neighbour-phases. Control of the oxygen partial pressure was achieved by buffer techniques. From the slopes of the lg σ vs. 1/T lines the activation energies were calculated for 10 kbar: 0.56 eV and 2.7 eV for Ni2SiO4 in equilibrium with SiO2 and Ni/NiO-buffer for the temperature range 500°–800°C and 800°–1,000°C resp. 0.52 eV for Fe2SiO4 in equilibrium with SiO2 and metallic iron, and 0.38 eV in equilibrium with SiO2 and magnetite; 1.11 eV for MgSiO3 in equilibrium with SiO2, and 1.25 eV in equilibrium with Mg2SiO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307562
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  • 2
    Electronic Resource
    Electronic Resource
    POWLS: A powder least-squares program (1979)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 483-485 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer program POWLS for refinement of crystal structures and magnetic structures from X-ray or neutron diffraction powder diagrams is reported. The program uses integrated intensities as the observed quantities. It is highly flexible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889879013091
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  • 3
    Electronic Resource
    Electronic Resource
    Refinement of simple crystal structures from synchrotron radiation powder diffraction data (1987)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 20 (1987), S. 394-401 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray powder diffractometry with storage-ring radiation was used to test various aspects of a method for refining simple crystal structures (Si, CeO2 and Co3O4). Excellent powder patterns were obtained with 0.17° resolution parallel slits and 1 Å X-rays. The intensities were determined with a double-Gaussian profile-fitting function and used in the powder least-squares refinement program POWLS. Except for Si, the peaks were broadened because of small particle sizes. The R(Bragg) values were in the range 0.4–1.7%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887086412
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal structures of quartz and magnesium germanate by profile analysis of synchrotron-radiation high-resolution powder data (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 182-191 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: High-resolution synchrotron-radiation powder data for quartz and Mg2GeO4, an olivine homologue, were obtained with a 365 mm long parallel-slit collimator with 0.05° aperture. The crystal structures were refined using a pseudo-Voigt profile fitting function and POWLS. Fourier maps were calculated from the measured structure factors of the germanate. The results for quartz were in good agreement with single-crystal data and R(Bragg) increased from 1.35 to 2.20% as the number of reflections included in the refinement increased from 46 to 119; the e.s.d.'s of the positional parameters were 4 to 8 × 10−4. The germanate gave R(Bragg) 4.85% using 77 Miller planes and the e.s.d.'s were 4 to 42 × 10−4. Special attention was given to the profile fitting function and the non-random particle distributions. The JCPDS Diffraction File Nos. will be reported in a later communication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887011567
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  • 5
    Electronic Resource
    Electronic Resource
    Profile fitting and the two-stage method in neutron powder diffractometry for structure and texture analysis (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 228-239 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An outline and an application of the two-stage method in neutron powder diffractometry are presented. Stage (1): Individual reflection data like position, half-width and integrated intensity are analysed by profile fitting. The profile analysis is based on an experimentally determined instrument function and can be applied without prior knowledge of a structural model. A mathematical procedure is described which results in a variance–covariance matrix containing standard deviations and correlations of the refined reflection parameters. Stage (2): The individual reflection data derived from the profile fitting procedure can be used for appropriate purposes either in structure determination or in texture and strain or stress analysis. The integrated intensities are used in the non-diagonal weighted least-squares routine POWLS for structure refinement. The weight matrix is given by the inverted variance-covariance matrix of stage (1). This procedure is the basis for reliable and real Bragg R values and for a realistic estimation of standard deviations of structural parameters. In the case of texture analysis the integrated intensities are compiled into pole figures representing the intensity distribution for all sample orientations of individual hkl. Various examples for the wide application of the two-stage method in structure and texture analysis are given: structure refinement of a standard quartz specimen, magnetic ordering in the system TbxY1−xAg, preferred orientation effects in deformed marble and texture investigations of a triclinic plagioclase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889888001013
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  • 6
    Electronic Resource
    Electronic Resource
    X-ray energy-dispersive diffractometry using synchrotron radiation (1977)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 10 (1977), S. 431-438 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The special features of X-ray energy-dispersive powder and single-crystal diffraction using synchrotron radiation are discussed on the basis of experiments performed at the Deutsches Elektronen-Synchrotron, DESY. The method is shown to be of particular value for fast structure identifications, experiments for which large scattering vectors are important, studies of phase transformations and chemical reactions at elevated temperatures and high-pressure studies. Studies of time-dependent phenomena using pulsed external fields are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889877013910
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  • 7
    Electronic Resource
    Electronic Resource
    Ytterbium LIII-edge anomalous scattering measured with synchrotron radiation powder diffraction (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 677-683 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The use of synchrotron powder diffraction patterns to determine anomalous scattering contributions is described. The method is illustrated by the determination of f' of Yb at the Yb LIII absorption edge. Four data sets were collected with four wavelengths, fitted with Gaussian profiles and the integrated intensities used to determine by least-squares methods the crystal-structure parameters and the real part f' of the anomalous dispersion. The derived f' values had a precision of ± 0.2 electron units and averaged 32% higher than the Cromer-Liberman theoretical values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876738709874X
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  • 8
    Electronic Resource
    Electronic Resource
    3,6-Dithia-3,4,5,5-tetrahydrophthalimide (1975)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 1973-1975 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740875006607
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  • 9
    Electronic Resource
    Electronic Resource
    The crystal structure of D-mannitol tris(benzeneboronic) ester, C24H23B3O6 (1977)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 33 (1977), S. 637-641 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740877004385
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  • 10
    Electronic Resource
    Electronic Resource
    (25R)-Cholest-5-ene-3β,26-diol (1977)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 33 (1977), S. 895-897 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740877004919
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