Journal of Applied Crystallography

Volume 37, Part 5 (October 2004)



[Issue Author Index][Volume Author Index]
[Cover illustration] Cover illustration: Volumetric visualization of electron density surrounding a histidine residue, allowing for direct observation of discrete disorder; generated with POVScript+ and rendered with POVRay. Courtesy of T. D. Fenn, D. Ringe & G. A. Petsko [J. Appl. Cryst. (2003), 36, 944-947].

research papers


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J. Appl. Cryst. (2004). 37, 683-697  [ doi:10.1107/S0021889804011446 ]

Exploratory orientation data analysis with [omega] sections

K. G. van den Boogaart and H. Schaeben

Synopsis: Pole point plots are generalized to augmented pole point plots visualizing a second crystallographic direction subjected to random orientations. [omega] sections of the space of crystallographic orientations generalizing both [gamma] as well as [sigma] sections are introduced into texture analysis and shown to visualize an orientation probability density function more instructively.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 698-702  [ doi:10.1107/S002188980401430X ]

Observation of orientational disorder in the hexagonal stuffed tridymite Sr0.864Eu0.136Al2O4 by the maximum-entropy method

H. Yamada, W. S. Shi and C. N. Xu

Synopsis: The crystal structure of a strontium europium aluminate, Sr0.864Eu0.136Al2O4, with a novel hexagonal form was investigated by a combination of Rietveld analysis and the maximum-entropy method with synchrotron X-ray powder diffraction data. The results suggest that AlO4 tetrahedra in Sr0.864Eu0.136Al2O4 are orientationally disordered.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 703-710  [ doi:10.1107/S0021889804012956 ]

Structure and order in lamellar phases determined by small-angle scattering

T. Frühwirth, G. Fritz, N. Freiberger and O. Glatter

Synopsis: Multilamellar phases can be identified and characterized by small-angle scattering of X-rays or neutrons. The recently developed generalized indirect Fourier transformation method is extended to determine simultaneously the structure factor and the model-free form factor.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 711-715  [ doi:10.1107/S0021889804014190 ]

X-ray diffuse scattering holography

M. Kopecký

Synopsis: It is shown that anomalous X-ray diffuse scattering can be treated as a hologram providing information on the local environment of the anomalous scatterer.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 716-723  [ doi:10.1107/S0021889804014657 ]

Study of geometrical local order in a non-ideal solid solution: an intermediary structure

M. Laridjani and F. Dénoyer

Synopsis: One of the key obstacles in the progress of certain aspects of solid-state physics is the determination of the nature of irregularities in the atomic network of matter and their correlation with macroscopic properties. In this work, an original structural result is presented, namely the presence of icosahedral clusters in an Al solid solution, as deduced from the analysis of the total Fourier-space image.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 724-731  [ doi:10.1107/S0021889804014876 ]

Powder pattern indexing with the dichotomy method

A. Boultif and D. Louër

Synopsis: A new computer program, DICVOL04, based on the successive dichotomy algorithm for powder diffraction pattern indexing is described. Many tests have revealed a high success rate.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 732-742  [ doi:10.1107/S0021889804015390 ]

Characterization and modelling of germanium assembled crystals for the diffraction of thermal neutrons

L. Alianelli, M. Sánchez del Río and R. Felici

Synopsis: Two assembled germanium crystals, produced for use as neutron monochromators, are characterized by means of neutron and X-ray diffraction. The neutron and synchrotron experimental data (reflectivity profiles and topographs) are compared with calculations based on analytical models and Monte Carlo simulations.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 743-749  [ doi:10.1107/S0021889804015638 ]

Full-profile refinement by derivative difference minimization

L. A. Solovyov

Synopsis: A new method of full-profile refinement is developed on the basis of a derivative difference minimization. The method allows powder diffraction structure analysis independently of the background and may also be applicable in many other areas.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 750-756  [ doi:10.1107/S002188980401581X ]

Small-angle scattering from spherical core-shell particles: an analytical scattering function for particles with Schulz-Flory size distribution

J. Wagner

Synopsis: The scattering function for spherical core-shell particles with a Schulz-Flory size distribution is derived. The analytical solution is applied to describe the small-angle scattering from core-shell systems with different particle size, polydispersity and ratio of core to shell radii.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 757-765  [ doi:10.1107/S0021889804016073 ]

X-ray imaging with ultra-small-angle X-ray scattering as a contrast mechanism

L. E. Levine and G. G. Long

Synopsis: A new transmission X-ray imaging technique using ultra-small-angle X-ray scattering (USAXS) as a contrast mechanism is described. USAXS imaging is complementary to USAXS and can provide quantitative and qualitative three-dimensional information on the sizes, shapes and spatial arrangements of the scattering objects.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 766-772  [ doi:10.1107/S0021889804016206 ]

Ab initio structure determination of the [Gamma] form of D-sorbitol (D-glucitol) by powder synchrotron X-ray diffraction

M. Rukiah, J. Lefebvre, O. Hernandez, W. van Beek and M. Serpelloni

Synopsis: The crystal structure of the [Gamma] form of D-sorbitol [C6H14O6, P21212, Z = 12, Z' = 3, a = 24.3012 (2), b = 20.5726 (2), c = 4.8672 (1) Å, V = 2433.30 (3) Å3] has been solved ab initio at 293 K from powder synchrotron X-ray diffraction data. A real-space method (Monte-Carlo simulated annealing), followed by Rietveld refinements with geometric soft restraints, has been used.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 773-777  [ doi:10.1107/S0021889804016310 ]

Lattice strain effects in the measurement of the Si lattice parameter by Laue-case double-crystal diffractometry

G. Mana, C. Palmisano and G. Zosi

Synopsis: The paper examines analytically and numerically the influence of a constant strain gradient on the rocking-curve peak location in a Laue-case double-crystal diffractometer.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 778-785  [ doi:10.1107/S0021889804015882 ]

Convergent-beam neutron crystallography

W. M. Gibson, A. J. Schultz, J. W. Richardson, J. M. Carpenter, D. F. R. Mildner, H. H. Chen-Mayer, M. E. Miller, E. R. Maxey and R. Youngman

Synopsis: The convergent-beam method for time-of-flight neutron crystallography using capillary optics can give expected integrated intensity gains of ~100 for a Bragg peak for samples as small as the focal spot (~100 µm). The diffracted beam intensities have expected gains greater than 500 for powder samples of similar dimensions.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 786-790  [ doi:10.1107/S002188980401698X ]

Performance of a new furnace for high-resolution synchrotron powder diffraction up to 1900 K: application to determine electron density distribution of the cubic CaTiO3 perovskite at 1674 K

M. Yashima and M. Tanaka

Synopsis: For accurate crystal structure analysis, a new electric furnace for the measurement of high-resolution ([delta]d/d = 0.03%) synchrotron radiation powder diffraction profiles from materials at high temperatures (up to 1900 K in air) has been designed and fabricated. The electron density distribution of cubic CaTiO3 perovskite at 1674 K indicates a covalent bond between Ti and O atoms.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 791-801  [ doi:10.1107/S0021889804017583 ]

About the efficiency of the early FOMs in ab initio protein phasing

M. C. Burla, R. Caliandro, B. Carrozzini, G. L. Cascarano, L. De Caro, C. Giacovazzo and G. Polidori

Synopsis: Several early figures of merit (FOMs) are tested for their ability to speed up ab initio protein phasing. A new combined FOM is proposed.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 802-807  [ doi:10.1107/S0021889804017820 ]

Disordered quasicrystals: diffuse scattering in decagonal Al-Ni-Fe

E. Weidner, F. Frey, J.-L. Lei, B. Pedersen, C. Paulmann and W. Morgenroth

Synopsis: Interpretation of diffuse scattering of decagonal Al-Ni-Co is presented, based on thermal diffuse scattering and Huang diffuse scattering contributions.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 808-814  [ doi:10.1107/S0021889804017832 ]

Energetic materials: variable-temperature crystal structures of [gamma]- and [epsilon]-HNIW polymorphs

N. B. Bolotina, M. J. Hardie, R. L. Speer Jr and A. A. Pinkerton

Synopsis: Temperature-dependent (in the range 100-298 K) changes of the crystal lattices of [gamma]- and [epsilon]-hexanitrohexaazaisowurtzitane have been evaluated from the second-rank thermal expansion tensors. Both lattices undergo anisotropic thermal expansion, that of [gamma]-HNIW being more anisotropic than that of the [epsilon] phase.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 815-822  [ doi:10.1107/S0021889804017959 ]

Interpretation of small-angle scattering data of inhomogeneous ellipsoids

G. Fritz and A. Bergmann

Synopsis: The parameters that can be obtained by indirect Fourier transformation of small-angle scattering data of inhomogeneous ellipsoids are discussed. Application of this method to experimental SAXS and SANS data is described.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 823-831  [ doi:10.1107/S0021889804018096 ]

Contribution of powder diffraction for structure refinements of aperiodic misfit cobalt oxides

D. Grebille, S. Lambert, F. Bourée and V. Petrícek

Synopsis: Misfit cobalt oxide phases Ca3Co4O9 and Ca0.82(Cu0.65Co0.35O2) have been reinvestigated by Rietveld structure refinements using neutron and synchrotron diffraction data and new insights are given for these complex structures.

Online 11 September 2004


teaching and education


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J. Appl. Cryst. (2004). 37, 832-835  [ doi:10.1107/S0021889804016048 ]

HELIX: a helical diffraction simulation program

C. Knupp and J. M. Squire

Synopsis: The program HELIX has been devised as a simple aid to understanding the origin and appearance of fibre diffraction patterns from helical structures.

Online 11 September 2004


laboratory notes


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J. Appl. Cryst. (2004). 37, 836-840  [ doi:10.1107/S0021889804014499 ]

Re-thinking the role of the beamstop at a synchrotron-based protein crystallography beamline

R. W. Alkire, R. Schuessler, F. J. Rotella, J. D. Gonczy and G. Rosenbaum

Synopsis: A 1 mm vertical-profile X-ray beamstop has been designed to operate in the energy range 6-20 keV. The relationship between the beamstop-to-sample distance and air scatter is discussed with the intent of establishing criteria for optimal beamstop positioning during an experiment.

Online 11 September 2004


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J. Appl. Cryst. (2004). 37, 841-842  [ doi:10.1107/S002188980401564X ]

X-ray diffuser

Y. Matsuura, I. Yoshizaki and M. Tanaka

Synopsis: An X-ray diffuser which causes broadening of the synchrotron beam divergence has been developed and used successfully by inserting an amorphous boron powder plate.

Online 11 September 2004


computer program abstracts


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J. Appl. Cryst. (2004). 37, 843-844  [ doi:10.1107/S0021889804018047 ]

HKL2MAP: a graphical user interface for macromolecular phasing with SHELX programs

T. Pape and T. R. Schneider

Synopsis: To simplify the use of the SHELX programs for phasing and as a teaching tool, a graphical user interface, HKL2MAP has been developed.

Online 11 September 2004


books received


 

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J. Appl. Cryst. (2004). 37, 845  [ doi:10.1107/S002188980402059X ]

X-ray scattering from semiconductors

Online 11 September 2004


 

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J. Appl. Cryst. (2004). 37, 845  [ doi:10.1107/S0021889804021727 ]

Epitaxy. Physical principles and technical implementation

Online 11 September 2004


 

J. Appl. Cryst. (2004). 37, 845-846

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