Journal of Applied Crystallography

Volume 35, Part 4 (August 2002)

Cover illustration: The crystal structure of titanite, CaTiOSiO4, viewed down the direction of the octahedral TiO6 chains. The full green lines indicate a unit cell of the two-dimensional Ising model, used to predict diffuse scattering intensity observable in layers normal to the chain direction. Ti atoms are shown in green, Ca in light grey, O in blue. The thinner red lines are Si-O bonds, the thick red lines Ti-O1 bonds. Courtesy of T. Malcherek, C. Paulmann, M. C. Domeneghetti & U. Bismayer [J. Appl. Cryst. (2001), 34, 108-113].

• research papers
• short communications
• laboratory notes
• computer program abstracts
• meetings

research papers

J. Appl. Cryst. (2002). 35, 383-400  [ doi:10.1107/S0021889802008798 ] Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals N. V. Y. Scarlett, I. C. Madsen, L. M. D. Cranswick, T. Lwin, E. Groleau, G. Stephenson, M. Aylmore and N. Agron-Olshina Synopsis: This second part of a round robin on the determination of quantitative phase abundance from diffraction data addresses problems including preferred orientation, the analysis of amorphous content, microabsorption, complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. It is concluded that the greatest physical obstacle to accurate quantitative phase analysis for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 401-405  [ doi:10.1107/S0021889802005824 ] The calculation of a parent grain orientation from inherited variants for approximate (b.c.c.-h.c.p.) orientation relations M. Humbert and N. Gey Synopsis: The paper describes a method based on orientation distances for evaluating the orientation of a parent b.c.c. (body-centred cubic) grain from several h.c.p. (hexagonal close packed) inherited variants in the case of an approximate (b.c.c.-h.c.p.) orientation relation. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 406-421  [ doi:10.1107/S0021889802006088 ] IsGISAXS: a program for grazing-incidence small-angle X-ray scattering analysis of supported islands R. Lazzari Synopsis: The purpose of the IsGISAXS program is to simulate and analyse grazing-incidence small-angle X-ray scattering of islands on a substrate in the distorted-wave Born approximation. Various island shapes and repartitions on the substrate are encompassed in the program. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 422-429  [ doi:10.1107/S0021889802006556 ] Completion of crystal structure by powder diffraction data: a new method for locating atoms with polyhedral coordination C. Giacovazzo, A. Altomare, C. Cuocci, A. G. G. Moliterni and R. Rizzi Synopsis: A new method able to locate cations and surrounding anions in tetrahedral or octahedral coordination is described. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 430-433  [ doi:10.1107/S0021889802006817 ] Reflection of waveguided X-rays in two-dimensional nanostructures F. Pfeiffer, T. Salditt and C. David Synopsis: The internal reflection of an excited X-ray waveguide mode at an internal lateral boundary in a synthetic nanostructure has been measured. The experiment constitutes an important step towards the production of a coherent nanometre-sized X-ray point source by two-dimensionally defined waveguide structures. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 434-442  [ doi:10.1107/S0021889802006829 ] X-ray diffraction, neutron scattering and EXAFS spectroscopy of monoclinic zirconia: analysis by Rietveld refinement and reverse Monte Carlo simulations M. Winterer, R. Delaplane and R. McGreevy Synopsis: Extended X-ray absorption fine structure (EXAFS) and neutron scattering data from monoclinic zirconia are analysed independently and simultaneously by reverse Monte Carlo (RMC) modelling; analysis of EXAFS spectra by RMC modelling results in reliable and accurate information on the local structure consistent with neutron scattering and X-ray diffraction experiments. A simultaneous analysis of neutron scattering and EXAFS data provides more complete information on the local structure than the analysis of the independent data sets. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 443-454  [ doi:10.1107/S0021889802007835 ] Molecular, crystallographic and algorithmic factors in structure determination from powder diffraction data by simulated annealing K. Shankland, L. McBride, W. I. F. David, N. Shankland and G. Steele Synopsis: Factors influencing the performance of a simulated-annealing approach to the determination of molecular crystal structures from X-ray powder diffraction data are investigated. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 455-458  [ doi:10.1107/S0021889802008038 ] Triangular dendrites of LiAlSiO4-SiO2: evolution between threefold- and sixfold-symmetric morphologies S. R. Zhao, J. Tan, J. Y. Wang, X. B. Hu and H. Liu Synopsis: A special kind of triangular dendrite of LiAlSiO4-SiO2 (or Li1-xAl1-xSi1+xO4, 0 x 1) in matt glaze has been observed by DIC (differential interference contrast) microscopy. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 459-470  [ doi:10.1107/S0021889802008440 ] Three-dimensional Pt-nanoparticle networks studied by anomalous small-angle X-ray scattering and X-ray absorption spectroscopy T. Vad, H.-G. Haubold, N. Waldöfner and H. Bönnemann Synopsis: Metal-organic networks formed by crosslinking aluminium-organic-stabilized platinum nanoparticles with bifunctional spacer molecules are investigated by anomalous small-angle X-ray scattering. For the structural characterization, a model function for a multicomponent system of hard spheres is proposed and applied to three different samples; the results are compared with those obtained from X-ray absorption measurements and the application of Fourier methods (characteristic function). Online 18 July 2002

J. Appl. Cryst. (2002). 35, 471-476  [ doi:10.1107/S0021889802008403 ] A pixel detector with large dynamic range for high photon counting rates J.-F. Bérar, L. Blanquart, N. Boudet, P. Breugnon, B. Caillot, J.-C. Clemens, P. Delpierre, I. Koudobine, C. Mouget, R. Potheau and I. Valin Synopsis: The use of pixel detectors at synchrotron beams is described. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 477-480  [ doi:10.1107/S0021889802008580 ] On the handling of atomic anisotropic displacement parameters R. W. Grosse-Kunstleve and P. D. Adams Synopsis: Theoretical and practical aspects of handling atomic anisotropic displacement parameters are discussed. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 481-490  [ doi:10.1107/S0021889802008737 ] Quantitative phase analysis by combining the Rietveld and the whole-pattern decomposition methods C. Giannini, A. Guagliardi and R. Millini Synopsis: A method is described to combine the Rietveld and the whole-pattern decomposition techniques for the quantitative phase analysis of mixtures containing phases with unknown or imperfectly known crystal structure. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 491-496  [ doi:10.1107/S0021889802009032 ] Modeling growth and equilibrium form of -SiO2 M. F. Nicolov and C. F. Woensdregt Synopsis: Computation of attachment energies, which are considered to be directly related to the growth rates of the corresponding F faces, has been performed using an electrostatic point-charge model, taking into account Born repulsion and van der Waals contributions computed by means of the Gilbert equation or the van Beest and van Santen short-range potentials. Online 18 July 2002

J. Appl. Cryst. (2002). 35, 497-504  [ doi:10.1107/S0021889802009044 ] Mapping of unstressed lattice parameters using pulsed neutron transmission diffraction J. R. Santisteban, A. Steuwer, L. Edwards, P. J. Withers and M. E. Fitzpatrick Synopsis: The Bragg edges appearing in time-of-flight neutron transmission experiments are used in combination with the sin2 technique to map the spatial variation of the unstressed lattice parameter in a ferritic weld. The technique is first introduced and then validated on a specially prepared biaxially stressed sample before use on a ferritic steel weld. Online 18 July 2002

short communications

J. Appl. Cryst. (2002). 35, 506-508  [ doi:10.1107/S002188980200972X ] Neutron diffraction studies of collagen in human cancellous bone J. M. S. Skakle and R. M. Aspden Synopsis: Neutron diffraction data have, for the first time, been recorded from collagen in cancellous human bone. Online 18 July 2002

laboratory notes

J. Appl. Cryst. (2002). 35, 509-510  [ doi:10.1107/S0021889802007227 ] A modular plate for the optimization of protein crystallization conditions B. Lorber and R. Cudney Synopsis: A modular protein crystallization plate is described. Online 18 July 2002

computer program abstracts

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