(IUCr) Contents for Acta Crystallographica Section A Vol. 61 Part 4 (July 2005)

Acta Cryst. (2005). A61, 387-396 [ doi:10.1107/S0108767305010044 ]

X-ray diffraction by a crystal in a permanent external electric field: general considerations

S. V. Gorfman, V. G. Tsirelson and U. Pietsch

Synopsis: The change of X-ray diffraction intensities in the presence of a permanent external electric field is modeled in terms of a stationary perturbation theory. Small atomic displacements within a unit cell are recognized as the major origin of structure-factor variations induced by an external electric field. An optimum strategy for X-ray synchrotron diffraction data collection is proposed and assessed using the example of [alpha] -GaPO₄, considering the limitations of up-to-date experiments.

Online 23 June 2005

Acta Cryst. (2005). A61, 397-404 [ doi:10.1107/S0108767305011293 ]

Quantitative structure retrieval using scanning transmission electron microscopy

S. D. Findlay

Synopsis: A method is described that reconstructs the projected object from coherent images recorded using a scanning transmission electron microscope.

Online 23 June 2005

Acta Cryst. (2005). A61, 405-410 [ doi:10.1107/S0108767305012997 ]

Growth process of the ridge-trough faces of a twinned crystal

J.-W. Lee, U.-J. Chung, N. M. Hwang and D.-Y. Kim

Synopsis: The growth process of the ridge-trough faces of a twinned crystal is analyzed.

Online 23 June 2005

Acta Cryst. (2005). A61, 411-417 [ doi:10.1107/S0108767305013231 ]

Electron-density distribution in cubic SrTiO₃: a comparative -ray diffraction study

W. Jauch and M. Reehuis

Synopsis: The electron density of cubic SrTiO₃ has been determined from high-quality [gamma] -ray diffraction data and is compared with results reported earlier.

Online 23 June 2005

Acta Cryst. (2005). A61, 418-425 [ doi:10.1107/S0108767305014790 ]

Improved data acquisition in grazing-incidence X-ray scattering experiments using a pixel detector

C. M. Schlepütz, R. Herger, P. R. Willmott, B. D. Patterson, O. Bunk, Ch. Brönnimann, B. Henrich, G. Hülsen and E. F. Eikenberry

Synopsis: Use of an area pixel detector using single-photon counting technology has improved the speed of data acquisition and their reliability in grazing-incidence X-ray diffraction experiments at the Swiss Light Source, Paul Scherrer Institute.

Online 23 June 2005

Acta Cryst. (2005). A61, 426-434 [ doi:10.1107/S0108767305014807 ]

On the density of homogeneous sphere packings

E. Koch, H. Sowa and W. Fischer

Synopsis: For some types of sphere packing with typical one- and two-dimensional parameter regions, the sphere-packing density as a function of the free parameters is discussed. Some sphere-packing types with extraordinary density properties are presented.

Online 23 June 2005

Acta Cryst. (2005). A61, 435-444 [ doi:10.1107/S0108767305016223 ]

Tetragonal sphere packings: minimal densities and subunits

W. Fischer

Synopsis: For all 382 types of homogeneous sphere packings with tetragonal symmetry, minimal sphere-packing densities and sample coordinates are presented. 1- and 2-periodic subunits of these sphere packings are tabulated in addition.

Online 23 June 2005

Acta Cryst. (2005). A61, 445-452 [ doi:10.1107/S010876730501648X ]

Polynomial-time algorithms for the integer minimal principle for centrosymmetric structures

A. Vaia and N. V. Sahinidis

Synopsis: Two polynomial-time algorithms are developed to solve the integer minimal principle for centrosymmetric structures. These algorithms rely on fast linear algebra techniques to solve the phase problem entirely in reciprocal space.

Online 23 June 2005

Acta Cryst. (2005). A61, 453-459 [ doi:10.1107/S0108767305017630 ]

Refinement of the crystal structural parameters of La_2/3Ca_1/3MnO₃ using quantitative convergent-beam electron diffraction

F. Feng, J. Zhu and A. Zhang

Synopsis: The structural parameters of La_0.67Ca_0.33MnO₃ were refined using one-dimensional HOLZ intensities by the QCBED method. It is feasible to obtain reliable structure information by this method and the global optimization algorithm.

Online 23 June 2005

Acta Cryst. (2005). A61, 460-470 [ doi:10.1107/S0108767305018064 ]

Three-beam resonant X-ray diffraction in germanium - Laue transmission cases

G. Thorkildsen, H. B. Larsen, E. Weckert, F. Mo and R. H. Mathiesen

Synopsis: Three-beam Laue-Laue transmission measurements in the vicinity of the K-absorption edge for a small slightly imperfect germanium crystal have been conducted. These reveal that the apparent size of the crystalline medium responsible for the coherent interference is the most important quantity in the interpretation of the [psi] profiles. Some evidence points toward a small increase of the f' values close to the edge compared to tabulated ones.

Online 23 June 2005

Acta Cryst. (2005). A61, 471-477 [ doi:10.1107/S010876730501809X ]

Outlier recognition in crystal-structure least-squares modelling by diagnostic techniques based on leverage analysis

M. Merli

Synopsis: The application of statistical diagnostic methods based on leverage analysis to assess the suitability of the results of a crystal-structure model refinement is presented and discussed.

Online 23 June 2005

short communications

Acta Cryst. (2005). A61, 478-480 [ doi:10.1107/S0108767305015266 ]

Rapid calculation of RMSDs using a quaternion-based characteristic polynomial

D. L. Theobald

Synopsis: Using a quaternion-based characteristic polynomial, a simple algorithm is developed that rapidly and stably determines root mean square deviations for structural superpositions.

Online 23 June 2005

Acta Crystallographica Section A

Foundations of Crystallography

Volume 61, Part 4 (July 2005)

research papers

X-ray diffraction by a crystal in a permanent external electric field: general considerations

S. V. Gorfman, V. G. Tsirelson and U. Pietsch