Acta Crystallographica Section A

Foundations of Crystallography

Volume 54, Part 1 (January 1998)

Cover illustration: Power spectrum of a high-resolution electron-microscopy image of NiAl <110>. The image calculation includes a realistic phonon spectrum by coupling the `molecular dynamics' and `multislice' simulation techniques. The diffuse background, satellite peaks and bands mirror the effect of thermal diffuse scattering and correlated atom vibrations. Courtesy of G. Möbus, T. Gemming and P. Gumbsch.

• international union of crystallography
• research papers
• short communications

international union of crystallography

Acta Cryst. (1998). A54, 1-6    [doi:10.1107/S0108767398099991]

Notes for Authors

research papers

Acta Cryst. (1998). A54, 7-18    [doi:10.1107/S010876739700874X]

Direct Inversion of Dynamical Electron Diffraction Patterns to Structure Factors

J. C. H. Spence

Synopsis: An exact nonperturbative inversion method is described for transmission electron diffraction which allows crystal structure factors to be obtained directly from the intensities of multiply scattered Bragg beams.

Acta Cryst. (1998). A54, 19-30    [doi:10.1107/S0108767397010106]

Symmetry-Mode Analysis of Displacive Phase Transitions using International Tables for Crystallography

M. I. Aroyo and J. M. Perez-Mato

Synopsis: A procedure for the determination of the primary and secondary modes necessary for the symmetry-mode analysis of structural phase transitions is presented. The method only requires the use of International Tables for Crystallography, Vol. A.

Acta Cryst. (1998). A54, 31-43    [doi:10.1107/S0108767397010295]

Hexamethylenetetramine Sebacate, an Incommensurate Structure with Large Nonsinusoidal Modulations: Comparison of Two Refinement Strategies

V. Bussien Gaillard, G. Chapuis, M. Dusek and V. Petrícek

Synopsis: Single crystals of the incommensurate organic salt hexamine sebacate present satellites up to sixth order. In the superspace approach, two refinement models based respectively on programs MSR and JANA are compared.

Acta Cryst. (1998). A54, 44-48    [doi:10.1107/S010876739701043X]

Reinvestigation of the Use of Patterson Maps to Extrapolate Data to Higher Resolution

D. A. Langs

Synopsis: A method is described for estimating the structure amplitudes of unmeasured reflections using a Patterson map computed with the measured data. Conditions for implementing the original idea, first put forward by Karle & Hauptman in 1964, are significantly improved.

Acta Cryst. (1998). A54, 49-60    [doi:10.1107/S0108767397010490]

Electron Ptychography. I. Experimental Demonstration Beyond the Conventional Resolution Limits

P. D. Nellist and J. M. Rodenburg

Synopsis: Electron ptychography is used to form an image at a resolution of three times the conventional limit of the microscope used. The accuracy of the experimental procedure is examined.

Acta Cryst. (1998). A54, 61-73    [doi:10.1107/S0108767397010507]

Electron Ptychography. II. Theory of Three-Dimensional Propagation Effects

T. Plamann and J. M. Rodenburg

Synopsis: The theory of three-dimensional and multiple scattering effects in electron ptychography is developed. Calculations indicate how these affect the interpretation of experimental results.

Acta Cryst. (1998). A54, 74-82    [doi:10.1107/S0108767397010593]

Theoretical Analysis of X-ray Standing Waves and Reflectivity in the Case of a Crystal Containing a Thin Buried Layer

Y. Zheng, J. C. Boulliard, B. Capelle and C. Malgrange

Synopsis: The X-ray propagation process in a crystal containing a thin buried layer is detailed. Direct consequences on the analysis of X-ray standing waves and reflectivity measurements are pointed out.

Acta Cryst. (1998). A54, 83-90    [doi:10.1107/S0108767397010957]

The Influence of Phonon Scattering on HREM Images

G. Möbus, T. Gemming and P. Gumbsch

Synopsis: The influence of thermal diffuse scattering on HREM simulations is found to be very tiny, proven by molecular-dynamics-simulated time series of frozen phonons in an NiAl crystal.

Acta Cryst. (1998). A54, 91-101    [doi:10.1107/S0108767397010489]

MSLS, a Least-Squares Procedure for Accurate Crystal Structure Refinement from Dynamical Electron Diffraction Patterns

J. Jansen, D. Tang, H. W. Zandbergen and H. Schenk

Synopsis: This paper shows that crystal structure refinement using electron diffraction data gives reliable results and good R values if the dynamical diffraction theory is used for the calculated intensities.

Acta Cryst. (1998). A54, 102-119    [doi:10.1107/S0108767397009963]

Corrections for Multiple Scattering in Integrated Electron Diffraction Intensities. Application to Determination of Structure Factors in the [001] Projection of Al_mFe

K. Gjønnes, Y. Cheng, B. S. Berg and V. Hansen

Synopsis: Approximate methods for treating dynamical scattering effects in integrated electron diffraction intensities from unknown structures are described. (hk0) structure factors of Al_mFe are determined ab initio from a combination of CBED and integrated intensities.

Acta Cryst. (1998). A54, 120-128    [doi:10.1107/S0108767397010362]

Three-Beam Diffraction in Finite Perfect Crystals. I. Exploring Laue-Laue and Bragg-Laue Scattering Using a Series-Expansion Approach for the Solution of the Takagi-Taupin Equations

G. Thorkildsen and H. B. Larsen

Synopsis: Analytical expressions for profiles are obtained by using the boundary-value Green-function technique. The results indicate a strong dependence on the crystal shape.

Acta Cryst. (1998). A54, 129-136    [doi:10.1107/S0108767397010659]

Three-Beam Diffraction in Finite Perfect Crystals. II. Influence of Absorption, Resonant Scattering and Polarization

H. B. Larsen and G. Thorkildsen

Synopsis: Using the boundary-value Green-function technique in the solution of the Takagi-Taupin equations, it is shown how absorption, resonant scattering and polarization affect the dynamical interactions and cause changes of profiles.

Acta Cryst. (1998). A54, 137-145    [doi:10.1107/S010876739701088X]

Three-Beam Diffraction in Finite Imperfect Crystals. An Analysis of Coherent Wavefield Interactions Using Statistical Dynamical Theory

H. B. Larsen and G. Thorkildsen

Synopsis: The concepts of statistical dynamical theory are implemented in the Takagi-Taupin equations. Using the boundary-value Green-function technique, analytical solutions for the coherent diffracted power is obtained and the influence on profiles is discussed.

short communications

Acta Cryst. (1998). A54, 146    [doi:10.1107/S0108767397012051]

The pseudo-atom approach to phase determination in protein electron crystallography - noncentrosymmetric projections. Erratum

D. L. Dorset

Synopsis: Erratum to Acta Cryst. (1997), A 53, 445-455.

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