Journal of Applied Crystallography

Volume 34, Part 3 (June 2001)



[Issue Author Index][Volume Author Index]
[Cover illustration] Cover illustration: Diffuse scattering around a 200 Bragg peak from a Cu-Ti single crystal (the intensities are in ln scale, the plane is (001), with the [100] direction horizontal, and the Bragg peak is masked by the blue beam stop). Courtesy of O. Lyon, C. Servant & J. P. Simon [J. Appl. Cryst. (2000), 33, 928-937].

research papers


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[HTML version][PDF version][CIF][3d view][Structure Factors][Supplementary Material]  [Buy article online]

J. Appl. Cryst. (2001). 34, 229-238  [ doi:10.1107/S0021889801000462 ]

X-ray structure study of the light-induced metastable states of the spin-crossover compound [Fe(mtz)6](BF4)2

J. Kusz, H. Spiering and P. Gütlich

Synopsis: The first X-ray study of the metastable states of a spin-crossover compound is presented, including spin transition without volume change.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 239-251  [ doi:10.1107/S0021889801001832 ]

String Fit: a new structurally oriented X-ray and neutron reflectivity evaluation technique

E. Politsch

Synopsis: String Fit is a novel molecular-structure-oriented neutron and X-ray reflectivity analysis method.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 252-257  [ doi:10.1107/S002188980100228X ]

The resolution function for a time-of-flight diffractometer with curved slits chopper

I. Ionita

Synopsis: A procedure for computing the resolution function for a time-of-flight diffractometer with curved slits chopper, using the matrix computation technique, is presented.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 258-262  [ doi:10.1107/S0021889801002254 ]

Neutron transmission through pyrolytic graphite monochromators

D. F. R. Mildner, M. Arif and S. A. Werner

Synopsis: Thermal neutron transmission measurements have been made as a function of wavelength on a pyrolytic graphite monochromator crystal that has been set to diffract a horizontal beam at different take-off angles. With respect to multi-instrument beamline design, the data show that it is best for a monochromator with the greatest (horizontal) take-off angle to be placed upstream, while monochromators with decreasing take-off angles should be placed progressively further downstream.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 263-270  [ doi:10.1107/S0021889801002497 ]

The determination of a stress-free lattice parameter within a stressed material using elastic anisotropy

M. R. Daymond and M. W. Johnson

Synopsis: This paper describes a method for the calculation of a stress-free lattice parameter from the analysis of diffraction data, utilizing the elastic anisotropy of a stressed material. The technique is demonstrated using data from a uniaxial load test.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 271-279  [ doi:10.1107/S0021889801002898 ]

The determination of site occupancies using a new strategy in Rietveld refinements

M. Heuer

Synopsis: A refinement strategy based on a bivariate analysis with a stepwise truncation of low-order reflection data and a rejection of outliers (LOT analysis), which had successfully been applied to X-ray single-crystal data, is applied to Rietveld refinements. Model calculations and refinements show an improvement in the determination of the site occupancy factors when the LOT strategy is used.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 280-288  [ doi:10.1107/S0021889801003077 ]

Orientation distribution analysis in deformed grains

J. C. Glez and J. Driver

Synopsis: Some improvements are proposed for the statistical analysis of orientation data within individual grains, in particular by allowing for crystallographic symmetries. A method based on quaternions is then presented to characterize orientation spreads including anisotropic effects.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 289-297  [ doi:10.1107/S0021889801003260 ]

Time-of-flight neutron transmission diffraction

J. R. Santisteban, L. Edwards, A. Steuwer and P. J. Withers

Synopsis: The Bragg edges appearing in time-of-flight neutron transmission experiments of polycrystalline materials are used to define lattice parameters precisely. The technique is specially suited for very fast characterization of bulk samples as well as for mapping spatial changes in the lattice parameter and hence the strain in engineering samples.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 298-310  [ doi:10.1107/S0021889801003715 ]

Crystallite size distribution and dislocation structure determined by diffraction profile analysis: principles and practical application to cubic and hexagonal crystals

T. Ungár, J. Gubicza, G. Ribárik and A. Borbély

Synopsis: Two different methods of diffraction peak profile analysis are suggested for the determination of microstructural parameters in terms of crystallite size distribution and dislocation structure. The first is based on modified Williamson-Hall and Warren-Averbach procedures; the second is a whole-profile fitting by using the Fourier coefficients of ab initio size and strain profiles.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 311-317  [ doi:10.1107/S0021889801004046 ]

A new X-ray powder diffractometer working in the 87-1000 K range for phase-transition analyses

F. Sayetat and A. Prat

Synopsis: The new diffractometer is devoted to the detection of phase transitions, to the determination of thermal expansion curves and to the study of kinetic chemical reactions in situ. The apparatus has been tested by measuring the cell parameter of the standard material cubic Na2Ca3Al2F14 in the 90-600 K range, and by measuring the thermal expansion of the cell parameter of cubic AgI in the 303-553 K range, revealing a first-order phase transition.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 318-324  [ doi:10.1107/S0021889801004332 ]

Background estimation using a robust Bayesian analysis

W. I. F. David and D. S. Sivia

Synopsis: A novel method for the estimation of the background in a powder diffraction pattern has been developed using a robust Bayesian analysis. The underlying probability theory is discussed in terms of going beyond the Gaussian approximation normally associated with counting statistics and least-squares analysis, and various examples are presented that illustrate the general applicability of the approach.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 325-329  [ doi:10.1107/S0021889801004745 ]

Computer simulation approach to reliability and accuracy in EXAFS structural determinations

P. Ghigna, M. Di Muri and G. Spinolo

Synopsis: The fit of a set of simulated noisy EXAFS (extended X-ray absorption fine structure) spectra can be used to sample the frequency distribution of structural parameters and provide their statistical estimators (mean, dispersion, correlations).

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 330-335  [ doi:10.1107/S002188980100468X ]

Polycapillary optic-source combinations for protein crystallography

F. A. Hofmann, W. M. Gibson, C. A. MacDonald, D. A. Carter, J. X. Ho and J. R. Ruble

Synopsis: A systematic study of the application of collimating and slightly focusing polycapillary optics to the X-ray crystallographic structure determination of egg-white lysozyme using two different sources, a standard rotating anode source and a low-power table-top microfocusing source, is presented.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 336-342  [ doi:10.1107/S0021889801004691 ]

Neural network application to the inverse scattering problem in high-resolution X-ray diffraction

C. Glorieux and E. Zolotoyabko

Synopsis: The complicated inverse scattering problem of reconstructing depth-dependent lattice parameters from high-resolution X-ray diffraction spectra is analysed by using neural networks. Attention is paid to the practically important case of structural modifications in the near-surface layers of ion-implanted single crystals.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 343-357  [ doi:10.1107/S0021889801005106 ]

Neutron imaging with bent perfect crystals. I. Imaging conditions

A. D. Stoica, M. Popovici and C. R. Hubbard

Synopsis: Neutron imaging with bent crystals is considered in the linear approximation of neutron optics. A matrix formalism analogous to that of conventional lens optics is developed.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 358-364  [ doi:10.1107/S0021889801005064 ]

Application of quantitative texture analysis to Rietveld profile refinement of neutron diffraction patterns of a zircaloy sample

Y. C. Kim, B. S. Seong, J. H. Lee and E. J. Shin

Synopsis: The possibility of extending the Rietveld method to incorporate textured polycrystalline materials is demonstrated with a zircaloy sample. By assigning the pole densities obtained by separate texture analysis to the preferred orientation factors in the mathematical model of the Rietveld method, good profile refinement results are achieved with the neutron diffraction patterns.

Online 22 May 2001


cryocrystallography papers


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J. Appl. Cryst. (2001). 34, 365-370  [ doi:10.1107/S0021889801003697 ]

Crystallization and cryocrystallography inside X-ray capillaries

F. J. López-Jaramillo, J. M. García-Ruiz, J. A. Gavira and F. Otálora

Synopsis: The feasibility of growing isolated protein crystals inside X-ray capillaries from gelled solutions of proteins has been demonstrated experimentally. Using these same X-ray capillaries, X-ray diffraction data were collected at both room temperature and 100 K.

Online 22 May 2001


teaching and education


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[HTML version][PDF version]  [Open access]

J. Appl. Cryst. (2001). 34, 371-374  [ doi:10.1107/S0021889801003624 ]

Integrating biocrystallography into traditional biology and chemistry curricula

M. Jaskólski

Synopsis: New academic courses for teaching protein crystallography to biology and chemistry students have been developed. They include model-building exercises using adapted general-purpose kits and application of Web tools for practical classes and for conducting educational/examination quizzes.

Online 22 May 2001


short communications


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J. Appl. Cryst. (2001). 34, 375-380  [ doi:10.1107/S0021889801003053 ]

A citation analysis of the Cambridge Crystallographic Data Centre

J. Redman, P. Willett, F. H. Allen and R. Taylor

Synopsis: A citation analysis of papers published by the CCDC for the period 1981-1998 shows rapidly increasing citation frequencies over time, over journals and over geographical regions. The ten most highly cited papers, comprising database descriptions, geometrical tabulations and basic research papers, together received an average of 1058 citations per annum over the period 1995-1998.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 381-385  [ doi:10.1107/S0021889801004009 ]

Microstructural transformation of vanadium pentoxide powder obtained by high-energy vibrational ball-milling

P. Chatterjee, S. P. Sen Gupta and S. Sen

Synopsis: An X-ray powder diffraction profile analysis of ball-milled ceramic vanadium pentoxide samples reveals the development of nanostructure with significant plastic strain and its confinement.

Online 22 May 2001


 

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J. Appl. Cryst. (2001). 34, 386-387  [ doi:10.1107/S0021889801003685 ]

Optimization and planning of experiments in single-crystal diffractometry with a zero-dimensional detector

Yu. Nekrasov

Synopsis: An algorithm for the optimization of data collection is described. The algorithm ensures optimum quality of measurements at the set survey rate and operates efficiently and simply by the flexible distribution of time between first and second measurements of a reflection.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 388-391  [ doi:10.1107/S0021889801004666 ]

A simple and efficient innovation of the vapor-diffusion method for controlling nucleation and growth of large protein crystals

G. Li, Y. Xiang, Y. Zhang and D.-C. Wang

Synopsis: A simple innovation of the conventional vapor-diffusion method, involving the introduction of a capillary barrier (for hanging drop) or a punched film barrier (for sitting drop), has been set up. Crystallization experiments showed that this modified vapor-controlling-diffusion method is very effective for producing large protein crystals.

Online 22 May 2001


computer programs


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J. Appl. Cryst. (2001). 34, 392-397  [ doi:10.1107/S0021889801002904 ]

Quanto: a Rietveld program for quantitative phase analysis of polycrystalline mixtures

A. Altomare, M. C. Burla, C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori and R. Rizzi

Synopsis: The program Quanto is described; it is devoted to quantitative phase analysis of polycrystalline samples by means of the Rietveld method.

Online 22 May 2001


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J. Appl. Cryst. (2001). 34, 398-404  [ doi:10.1107/S0021889801003302 ]

Refinement of modulated structures against X-ray powder diffraction data with JANA2000

M. Dusek, V. Petrícek, M. Wunschel, R. E. Dinnebier and S. van Smaalen

Synopsis: A new version of the computer program JANA is introduced that allows Rietveld refinements of periodic and aperiodic crystal structures. Applications to (CO)xC60 and the incommensurately modulated structure of NbTe4 are presented.

Online 22 May 2001


computer program abstracts


 

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J. Appl. Cryst. (2001). 34, 405  [ doi:10.1107/S0021889801002928 ]

TWIN3.0 - a program for testing twinning by merohedry

V. Kahlenberg and T. Messner

Synopsis: The program TWIN3.0 is intended to test single-crystal data sets for the possible existence of twinning by merohedry.

Online 22 May 2001


addenda and errata


 

[HTML version][PDF version][Supplementary Material]  [Open access]

J. Appl. Cryst. (2001). 34, 406  [ doi:10.1107/S0021889801006008 ]

Estimation of cobalt coating layer thickness on acicular Fe3O4 powder using HR-TEM. Erratum

K. Sakai, H. Saguchi and T. Nishimura

Synopsis: Erratum to J. Appl. Cryst. (2001), 34, 102-107.

Online 22 May 2001


 

J. Appl. Cryst. (2001). 34, 407-408

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