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  • Digitale Medien  (27)
  • 1985-1989  (8)
  • 1980-1984  (19)
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Materialart
  • Digitale Medien  (27)
Erscheinungszeitraum
Jahr
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  • 1
    Digitale Medien
    Digitale Medien
    A miniature piston-cylinder apparatus for high-pressure X-ray diffraction in conjunction with energy dispersion (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 46-49 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A miniature piston-cylinder high-pressure cell has been constructed for experiments with energy-dispersive X-ray diffraction. The maximum pressure achieved was 37 × 108 Pa. Examples are given for KCl and MgO, both measured with NaCl as an internal standard. The phase transition in KCl has been observed and the CsCl structure type verified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S002188988001148X
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  • 2
    Digitale Medien
    Digitale Medien
    Crystal-structure refinement by profile fitting and least-squares analysis of powder diffractometer data (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 611-622 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: The refinement of crystal structures using X-ray powder data in a two-stage method is described. (1) The integrated intensities of the individual reflections are derived by a profile fitting method in which the profile shapes are accurately defined using an experimentally determined instrument function and the sum of Lorentzian curves. (2) These values are then used in a powder least-squares refinement for structure determination. The results obtained with three simple structures (silicon, quartz and corundum) gave R(Bragg) values of 0.7 to 2.5%. The necessity of correcting for preferred orientation and the importance of proper specimen preparation are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889883011176
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  • 3
    Digitale Medien
    Digitale Medien
    A new linear position-sensitive scintillation detector for neutron powder diffractometry (1984)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 17 (1984), S. 159-166 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A new linear position-sensitive scintillation detector has been developed and installed on a neutron powder diffractometer. The physical properties of this detector are described; test powder diffractograms are presented. The special advantages of this detector for neutron powder diffractometry are discussed: high detection efficiency also in the region of short wavelengths (75% for λ = 1.3 Å), good spatial resolution (FWHM = 2.5 mm), and high data-point density (Δ2θ = 0.02°). Special emphasis is placed on peak-profile analysis for the powder diffraction patterns. Examples for position and intensity separation of overlapping reflections are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889884011237
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889887086412
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889887011567
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889888001013
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S010876738709874X
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  • 8
    Digitale Medien
    Digitale Medien
    Bonding in [S2O6]2−: refinement and pictorial representation from an X-ray diffraction study of Na2S2O6.2H2O and Na2S2O6.2D2O (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 36 (1980), S. 512-523 
    Details
    ISSN: 1600-5740
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0567740880003743
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  • 9
    Digitale Medien
    Digitale Medien
    Charge density in anhydrite, CaSO4. II. Static deformation density distributions from a multipole refinement (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 525-532 
    Details
    ISSN: 1600-5740
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S056774088100352X
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  • 10
    Digitale Medien
    Digitale Medien
    X-ray diffraction study of Na2S2O6.2H2O and Na2S2O6.2D2O (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 36 (1980), S. 223-228 
    Details
    ISSN: 1600-5740
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S056774088000297X
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