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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of experimental and n-beam calculated intensities for glancing incidence high-energy electron diffraction (1972)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 28 (1972), S. 16-22 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Rocking curves for the 2nd to 7th order reflections of the systematic set from the (111) planes of a highly perfect silicon single crystal have been obtained in an ultra-high-vacuum reflection electron diffraction camera operated at 40 keV. These have been compared with the profiles computed with an n-beam dynamic high-energy electron diffraction theory adapted to the Bragg case at glancing incidence. It is shown that, for the 333 reflection, six nodes of the hhh row from {\bar 111} up to 444 are adequate to take into account the systematic multiple beam interference effects. The calculated widths are found to agree with the observed widths within the experimental error for all reflections. The peak reflectivities computed initially for a perfect semi-infinite crystal are systematically higher than the experimental values, by a factor of 7 for the 222 node, decreasing to near agreement for the 777 node. Possible reasons for such discrepancies are discussed. Neither inelastic scattering effects nor reasonable changes in the silicon lattice potential near the surface can bring the observed and calculated intensities into agreement. The discrepancy can be considerably reduced for all orders of reflection, however, when the non-flat nature of the surface is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739472000038
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple diffraction of X-rays and the phase problem. Computational procedures and comparison with experiment (1974)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 30 (1974), S. 413-423 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The general theory of n-beam X-ray diffraction (n 〉 2) has been developed in the framework of classical dynamical theory and applied to the Bragg case. It is shown that the crystal wave-vectors are the eigen-values of a 4n × 4n dispersion matrix. The boundary conditions are applied to a parallel-sided crystal slab and show that for an infinite thickness only 2n wave fields survive. The Umweganregung plot of Ge(222) with Cu Kα radiation has been considered in detail. The integrated intensity of an Umweganregung peak is defined here as a double integral with respect to θ (angle of incidence) and φ (azimuthal angle). The 222-113 and 222-{\bar 11}3 absolute integrated intensities were measured on a dislocation-free Ge crystal. Excellent agreement is obtained between experimental and calculated values. The ratio between the two integrated intensities (of the order of 7) did not change appreciably for a Ge mosaic crystal, although both reflections exhibited increases with respect to the perfect-crystal values. Since the two Umweganregung peaks considered in this experiment involve crystallographically equivalent reflections with different phases, it is suggested that the present technique can in principle be used for phase determination in crystal structure analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S056773947400091X
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  • 3
    Electronic Resource
    Electronic Resource
    Multiple diffraction effects in neutron single-crystal diffractometry (1972)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 28 (1972), S. 218-219 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The n-beam dynamical theory of diffraction is applied to multiple neutron diffraction. A computer program has been adapted to the neutron case from one originally developed for high energy electron diffraction in reflection. The integrated intensities are computed for the two and multibeam cases of the 002 reflection and compared with experiment. It is shown that only a negligible fraction of the incident beam satisfies the conditions for multiple diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739472000488
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  • 4
    Electronic Resource
    Electronic Resource
    Phonons: theory and experiment, I by P. Brüesch (1983)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 599-600 
    Details
    ISSN: 1600-5724
    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/S010876738300121X
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  • 5
    Electronic Resource
    Electronic Resource
    Phase observation in an organic crystal (benzil: C14H10O2) using long-wavelength X-rays (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 17-22 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The phase-related asymmetry effect near a multi-beam excitation point has been observed for a noncentrosymmetric organic crystal, benzil (C14H10O2), by using 3.5 keV X-ray synchrotron radiation. A multi-beam theoretical calculation shows good agreement with the experimental data when mosaic spread of the crystal is taken into account. A practical method to extract the cosine of the phase triplet for noncentrosymmetric crystals is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876738700713X
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  • 6
    Electronic Resource
    Electronic Resource
    Comment on The number of permitted modes of propagation in N-beam dynamical diffraction of X-rays by S. L. Chang (1980)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 36 (1980), S. 827-827 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Attention is directed to a previous treatment of multi-beam diffraction of X-rays by Colella [Acta Cryst. (1974), A30, 413-423]. The rules governing the number of permitted modes are discussed and compared with those given in a recent article by Chang [Acta Cryst. (1979), A35, 543-547].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739480001647
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  • 7
    Electronic Resource
    Electronic Resource
    Phase determination of the forbidden reflection 442 in silicon and germanium using multiple Bragg scattering (1985)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 451-453 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The sign inversion of the forbidden reflection 442 in silicon between room temperature and 700 K has been verified using multiple beam diffraction and the concept of virtual Bragg scattering. A similar determination in the case of germanium confirms that the 442 is mostly due to anharmonic effects at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767385000952
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  • 8
    Electronic Resource
    Electronic Resource
    n-Beam dynamical diffraction of high-energy electrons at glancing incidence. General theory and computational methods (1972)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 28 (1972), S. 11-15 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The n-beam dynamical theory of high-energy electrons is currently used in transmission (Laue case) for accurate determination of the Fourier components of the crystal potential. The same theory is expected to provide information about the surface potential when used to interpret diffraction patterns in reflection at glancing incidence (Bragg case). Some peculiar aspects are elucidated in detail, insofar that they are different from the transmission case, particularly the boundary conditions. Inelastic scattering effects are introduced by means of a complex potential. Changes of the Fourier components of the potential near the surface are considered, and a model has been developed which incorporates these changes into the theory. A slice treatment developed in the frame of Bethe's theory is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739472000026
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  • 9
    Electronic Resource
    Electronic Resource
    Temperature dependence of intensities from silicon with glancing incidence HEED (1973)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 29 (1973), S. 151-153 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Peak reflectivity for the 2nd to 7th order Bragg reflections of the hhh systematic set have been obtained at different temperatures. The results have been interpreted using an n-beam dynamical theory adapted to the Bragg case at glancing incidence. On the basis of this analysis it is concluded that the component of the mean-square vibrational amplitude of the surface atoms normal to the surface is about 40% greater than that of the bulk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739473000392
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  • 10
    Electronic Resource
    Electronic Resource
    Reply to Post's comments on my paper Multiple diffraction of X-rays and the phase problem. Computational procedures and comparison with experiment (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 155-155 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: It is shown that the errors in the paper by R. Colella [Acta Cryst. (1974). A30, 413-423] pointed out by B. Post [Acta Cryst. (1975). A31, 153-155] do not in fact exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475000289
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