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  • 1
    Electronic Resource
    Electronic Resource
    Three-beam and many-beam theory in electron diffraction and its use for structure-factor phase determination in non-centrosymmetric crystal structures (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 839-851 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Closed-form expressions for three-beam dynamical transmission electron diffraction are compared. These are used as a guide to determine the best experimental conditions for the determination of structure-factor phases by convergent-beam electron diffraction in the general non-systematic case. The validity domains of Kambe's [J. Phys. Soc. Jpn (1957), 12, 1-13] 'strong coupling' approximation and Bethe's [Ann. Phys. (Leipzig) (1928), 87, 55-129] second approximation are compared, and these approximations reconciled. A comparison of many-beam calculations with experimental non-systematic CBED patterns is used to determine a three-phase invariant for CdS with an accuracy of ±5° in the electron structure-factor phase. If it is assumed that two of the phases are known exactly, the error in the third (00\bar 2) X-ray structure-factor phase would be ±0.75°. The accuracy of the method for determining phases, atomic position parameters and bonding charge distributions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876738900913X
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  • 2
    Electronic Resource
    Electronic Resource
    Large dynamic range, parallel detection system for electron diffraction and imaging (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2102-2105 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A parallel detection system for electrons in the 10–800-kV energy range is described. The design is based on a 576×382 pixel charge-coupled device array operating at liquid-nitrogen temperature. This is coupled by fiber optics to a single-crystal YAG screen, which serves as the primary detection element. The performance of the system for quantitative electron diffraction and imaging studies is described. The system will record a maximum count of 16 000 per pixel with low noise at a frame rate of 2.5 frames per second.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140039
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  • 3
    Electronic Resource
    Electronic Resource
    Direct observation of d -orbital holes and Cu–Cu bonding in Cu 2 O (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 401 (1999), S. 49-52 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A striking feature of metal oxide chemistry is the unusual electronic and chemical behaviour of Cu(I) and Ag(I): a case in point is that detailed understanding of Cu–O bonding is essential to the theory of high-temperature copper oxide superconductors. Both cations are ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/43403
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  • 4
    Electronic Resource
    Electronic Resource
    Comment on "Electron holographic study of ferroelectric domain walls'' (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2446-2447 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109340
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of structure factor phase invariants from non-systematic many-beam effects in convergent-beam patterns
    Amsterdam : Elsevier
    Ultramicroscopy 26 (1988), S. 25-30 
    Details
    ISSN: 0304-3991
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0304-3991(88)90372-5
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  • 6
    Electronic Resource
    Electronic Resource
    Scanning system for high-energy electron diffractometry (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 1033-1038 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new electron diffractometer with a diffraction-pattern scanning system in front of a fixed counter has been developed. Significant improvement was achieved in the measured diffraction intensities by using fast electronics and additional control of the stability of the electron beam. The measurement of and accounting for the gear-frequency characteristic of the registration system was performed, and the signal accumulation mode for intensity measurements together with advanced statistical data processing were employed. Good agreement between the experimental and Hartree–Fock structure factors for LiF, NaF and MgO was achieved (to avoid strong extinction effects, rather thin polycrystalline films were used as samples).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889899006755
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  • 7
    Electronic Resource
    Electronic Resource
    Perturbation theory in high-energy transmission electron diffraction (1991)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 87-95 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A perturbation theory for many-beam high-energy transmission electron diffraction in noncentrosymmetric crystals is described for both the nondegenerate and degenerate cases. This perturbation theory differs from the conventional quantum-mechanical perturbation theory by perturbing the electron wavevectors instead of the total electron energy, which is constant for elastically scattered electrons. The relations between the perturbation theory and some other approximations commonly used in electron diffraction are discussed. It is shown that the few-beam approximation and the Kambe approximation are both applications of degenerate perturbation theory. Finally, as an example, this degenerate perturbation theory is applied to obtain an analytical solution to a four-beam case with two systematic (0 and g) and two nonsystematic (h and l) beams. This four-beam solution shows that the intensity of a four-beam interaction depends on all the four three-phase invariants involved, and also shows that the effects of the g beam on the three-beam interaction of 0, h and l are localized to the region near the Bragg condition of g. This may serve as a guide for future experiments using three-beam interactions for the measurement of structure-factor phases of an unknown structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876739001008X
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamic inversion by the method of generalized projections (1999)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 112-118 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new approach to the inversion problem of dynamical transmission electron diffraction is described, based on the method of generalized projections in set theory. An algorithm is described that projects between two sets of constrained scattering matrices. This iterative process can be shown to converge, giving the required structure factors (for some choice of origin) if the sets are convex. For the dynamical inversion problem, the set topology is that of an N2 torus, the sets are not convex, and traps are therefore sometimes encountered. These can be distinguished from solutions, allowing the algorithm to be restarted until a solution is found. Examples of successful inversion from simulated multiple-scattering data are given, which therefore solve the phase problem of electron diffraction for centrosymmetric or noncentrosymmetric crystal structures. The method may also be useful for the three-beam X-ray diffraction problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767398006977
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  • 9
    Electronic Resource
    Electronic Resource
    Anisotropic dispersion of the band structure and formation of ring patterns in CBED (1999)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 1026-1033 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: An off-axis ring pattern was observed in the \langle 1\bar{1}1 \rangle zone-axis CBED pattern of an NiO single crystal. The pattern was interpreted as resulting from anisotropic dispersion of the band structure of the two most strongly excited free Bloch waves and strong absorption of the most tightly bound 1s Bloch state. Comparison has also been made with the case of MgO which has the same structure as NiO but weaker scattering power. The tightly bound 1s Bloch state in MgO was found to play an important role together with a strongly excited free Bloch state and a more conventional zone-axis ring pattern similar to that observed in the \langle 001 \rangle zone-axis CBED pattern of silicon was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767399011125
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of individual structure-factor phases with tenth-degree accuracy: the 00.2 reflection in BeO studied by electron and X-ray diffraction (1993)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 422-429 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Measurements of the phase (and amplitude) of the 00.2 structure factor of BeO are reported. These were obtained by applying an automated least-squares refinement method to experimental convergent-beam transmission electron diffraction data, collected from sub-micrometer single-crystal regions of two different thicknesses. Multiple-scattering effects were included, using the Bloch-wave method. Perturbation methods were used to include weak beams and to estimate errors. After conversion to X-ray structure factors, it was found that φx (00.2) = −1.190 (9) rad. The same value was found, within experimental error, using data collected from a region of different thickness. New single-crystal X-ray results are also reported, which are in good agreement with the electron diffraction results. Phases derived from multipole refinement using X-ray data are about fifty times less accurate than the electron results. This electron diffraction technique may be the most accurate method for the measurement of low-order structure-factor phases from acentric crystals with small unit cells. The method may therefore allow the extension of previous highly accurate studies of charge density in silicon to acentric materials from which large single crystals cannot be grown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767392010699
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