Journal of Applied Crystallography

Contents of Volume 30, Part 6 (1 December 1997)

Cover illustration: A crystal of the protein phosphorylase b flash-cooled to 100 K in a 1 mm-diameter mohair loop prior to collection of X-ray diffraction data. Courtesy of Elspeth Garman and Stephen Lee, University of Oxford.

RESEARCH PAPERS

J. Appl. Cryst. (1997). 30, 889 - 892

X-ray Compton Scattering from Aluminium and Silicon Crystals at Low Scattering Angles

M. Yamada and M. Hida

Synopsis

A correction is shown for the Compton scattering intensity that is calculated theoretically for free atoms, if the loosely bound outer electrons of the atoms construct the conduction or valence band in crystals, typically in the case of aluminium and silicon.

J. Appl. Cryst. (1997). 30, 893 - 899

Neutron Powder Investigations of Zr_0.85Ca_0.15O_1.85 Sinter Material at Temperatures up to 1100 K and with a Simultaneously Applied Electric Field

H. Kahlert, H. Boysen and F. Frey

Synopsis

Atomic displacement parameters were derived from a temperature-factor analysis of Bragg reflections. An interpretation is given towards the migration of the oxygen ions under the action of an applied direct-current electric field.

J. Appl. Cryst. (1997). 30, 900 - 904

A New Small-Angle X-ray Scattering Instrument on the French CRG Beamline at the ESRF Multiwavelength Anomalous Scattering/Diffraction Beamline (D2AM)

J. P. Simon, S. Arnaud, F. Bley, J. F. Berar, B. Caillot, V. Comparat, E. Geissler, A. de Geyer, P. Jeantey, F. Livet and H. Okuda

Synopsis

The design and performance of the new SAXS modular instrument having easily variable wavelength are described. Tests reveal a previously unrecognized phenomenon, namely diffuse scattering from the mirrors; this can be reduced by rearrangement of the positions of the slits.

J. Appl. Cryst. (1997). 30, 905 - 908

X-ray Reflectometer for the Diagnostics of Thin Films During Growth

U. Niggemeier, K. Lischka, W. M. Plotz and V. Holy

Synopsis

A novel angular-dispersive X-ray reflectometer that allows the measurement of the X-ray reflectivity of thin layers, contained in a chamber, is described. The X-rays are focused by a Johansson monochromator using the Si(333) Bragg diffraction.

J. Appl. Cryst. (1997). 30, 909 - 913

Crystal Structure of Anilinium Pentamolybdate from Powder Diffraction Data. The Solution of the Crystal Structure by Direct Methods Package POWSIM

W. Lasocha and H. Schenk

Synopsis

The crystal structure of a layered compound containing 24 independent atoms was solved ab initio from X-ray laboratory powder data. The procedures applied are described. By powder diffraction study, the appropriate chemical formula was found.

J. Appl. Cryst. (1997). 30, 914 - 917

An Anomalous Small-Angle X-ray Scattering Study on Phase Decomposition in a Model Superalloy NiCrAl

F. Bley, F. Livet, O. Lyon, H. Okuda and J. P. Simon

Synopsis

Anomalous small-angle X-ray scattering measurements on the precipitation structure in an NiCrAl alloy have been performed. Ni partition was found to be the same in the matrix and the precipitates.

J. Appl. Cryst. (1997). 30, 918 - 920

Small-Angle X-ray Scattering of Heat-Treated Flame-Fused Silica Glass from Amorphous and Crystalline Powders

A. H. Shinohara, K. Omote, E. H. Sekiya, K. Shinoda, D. Torikai, C. K. Suzuki and C. A. C. Zavaglia

Synopsis

The effects of heat treatment on the structure of flame-fused silica glass from amorphous and crystalline powders were investigated by small-angle X-ray scattering.

J. Appl. Cryst. (1997). 30, 921 - 931

Adaptation of the Rietveld Method for the Characterization of the Lamellar Microstructure of Polymers

O. Dupont, A. M. Jonas and R. Legras

Synopsis

A variant of the Rietveld refinement procedure applied to the characterization by WAXS of disordered and small crystals as found in semi-crystalline polymers is described.

J. Appl. Cryst. (1997). 30, 932 - 942

Neutron Transmission Through Tapered Channels

D. F. R. Mildner, V. A. Sharov and H. H. Chen-Mayer

Synopsis

The radiation transmission characteristics of a tapered cylinder may be described using analytical expressions developed for the straight cylinder, but with a lower effective critical angle that depends on the taper length and angle.

J. Appl. Cryst. (1997). 30, 943 - 947

Study of Off-Specular Neutron Reflectivity Using a Model System

R. M. Richardson, J. R. P. Webster and A. Zarbakhsh

Synopsis

Off-specular neutron reflection from an optical grating has detected in-plane periodicity up to 42 micrometres. This is much longer than expected from the coherence length of the neutron beam but is consistent with the instrumental resolution.

J. Appl. Cryst. (1997). 30, 948 - 956

Small-Angle X-ray Scattering Experiments in Grazing Incidence on Sol-Gel Coatings Containing Nano-Scaled Gold Colloids: a New Technique for Investigating Thin Coatings and Films

B. Kutsch, O. Lyon, M. Schmitt, M. Mennig and H. Schmidt

Synopsis

Scattering of colloids is identified by variation of the X-ray energy near the absorption edge of gold. Results from small-angle X-ray scattering after correction for absorption and refraction are compared with high-resolution transmission electron microscopy and optical UV visible spectroscopy.

J. Appl. Cryst. (1997). 30, 957 - 962

An X-ray Charge-Density Feasibility Study at 56 keV of Magnesium Formate Dihydrate using a CCD Area Detector

H. Graafsma, S. O. Svensson and Å . Kvick

Synopsis

A high-resolution structural study of magnesium formate dihydrate was performed using high-energy synchrotron radiation and an X-ray image intensifier/CCD detector.

J. Appl. Cryst. (1997). 30, 963 - 967

Non-Gaussian Roughness of Interfaces: Cumulant Expansion in X-ray and Neutron Reflectivity

W. Press, J.-P. Schlomka, M. Tolan and B. Asmussen

Synopsis

A cumulant expansion was performed to calculate X-ray or neutron reflectivity.

J. Appl. Cryst. (1997). 30, 968 - 974

Crystal Structure Solution from Neutron Powder Diffraction Data by a new Monte Carlo Approach Incorporating Restrained Relaxation of the Molecular Geometry

M. Tremayne, B. M. Kariuki, K. D. M. Harris, K. Shankland and K. S. Knight

Synopsis

A new development of the Monte Carlo technique for structure solution from powder diffraction data, involving restrained relaxation of the geometry of the structural fragment during the Monte Carlo calculation, is reported.

J. Appl. Cryst. (1997). 30, 975 - 984

Small-Angle Neutron Scattering of Precipitates in Ni-Rich Ni-Ti Alloys. II. Methods for Analyzing Anisotropic Scattering Data

J. Skov Pedersen, P. Vysckocil, B. Schönfeld and G. Kostorz

Synopsis

A method for obtaining anisotropic correlation functions is presented and modelling of the scattering data by a modified paracrystal model is described.

See also Erratum: J. Appl. Cryst. (1996). 31, 490.

J. Appl. Cryst. (1997). 30, 985 - 995

Powder Diffraction Data and Crystal Chemical Information Combined in an Automated Structure Determination Procedure for Zeolites

R. W. Grosse-Kunstleve, L. B. McCusker and Ch. Baerlocher

Synopsis

The FOCUS method, in which both crystal chemical information and powder diffraction data are included in the structure determination process, is presented. FOCUS combines automatic Fourier recycling with a specialized topology search specific to zeolites.

J. Appl. Cryst. (1997). 30, 996 - 1001

Automatic Three-Dimensional Fourier Synthesis

V. B. Zlokazov

Synopsis

This paper describes an algorithm for peak search in the three-dimensional Fourier map that is more convenient and faster than conventional two-dimensional Fourier synthesis.

J. Appl. Cryst. (1997). 30, 1002 - 1007

A Novel Method of Analyzing Peak Broadening Due to Mosaicity for Cubic Crystals on (001) Substrate using Double-Crystal X-ray Diffraction Methods

K. Nakashima and H. Sugiura

Synopsis

A novel method of analyzing X-ray peak broadening due to mosaicity for double-crystal X-ray diffraction measurements is proposed.

J. Appl. Cryst. (1997). 30, 1008 - 1015

On the Peak Profiles in Energy-Dispersive Powder X-ray Diffraction with Synchrotron Radiation

J. W. Otto

Synopsis

The peak profiles of standard reference materials have been investigated with energy-dispersive X-ray diffraction at a synchrotron source. A single-line profile analysis was performed to obtain estimates of size and strain in plastically deformed f.c.c.-based metals.

J. Appl. Cryst. (1997). 30, 1016 - 1021

Growth and Structure of Thin Pt₂Si and PtSi Layers on Si(111) and (001) Characterized with In Situ Grazing Incidence Diffraction

C. Kumpf, R. Nicula and E. Burkel

Synopsis

Results from in situ grazing incidence diffraction and X-ray reflectivity measurements at different temperatures are presented. The structure, texture and epitaxic growth of thin Pt, Pt₂Si and PtSi layers on Si(111) and (001) surfaces are analyzed.

J. Appl. Cryst. (1997). 30, 1022 - 1025

MOLREP: an Automated Program for Molecular Replacement

A. Vagin and A. Teplyakov

Synopsis

An automated program for molecular replacement using a full-symmetry translation function combined with a packing function is described.

J. Appl. Cryst. (1997). 30, 1026 - 1035

Diffuse Interfaces and Small-Angle Scattering Intensity Behaviour

S. Ciccariello and R. Sobry

Synopsis

The oscillatory deviations arising from parallel interfaces, when the latter are diffuse, are still observable in the Porod plot provided that the ratio of the diffuse region thickness to the parallel interface distance is less than 1/4.

J. Appl. Cryst. (1997). 30, 1036 - 1040

An Algorithm for Automatic Indexing of Oscillation Images using Fourier Analysis

I. Steller, R. Bolotovsky and M. G. Rossmann

Synopsis

A fast and reliable algorithm has been developed for autoindexing oscillation images. The program has successfully determined the lengths and directions of basis vectors for numerous unit cells having cell dimensions ranging from 16 to 688 Å and oscillation ranges from 0.2 to 2.0 degrees.

J. Appl. Cryst. (1997). 30, 1041 - 1047

Kinetics of Decomposition in Copper-Cobalt: A Time-Resolved ASAXS Study

G. Goerigk, H.-G. Haubold and W. Schilling

Synopsis

Properties of the decomposition kinetics in Cu-Co alloys were determined by time-resolved ASAXS measurements.

J. Appl. Cryst. (1997). 30, 1048 - 1055

Small-Angle X-ray Scattering of Inorganic Glasses. Data Treatment and Analysis

G. Walter, R. Kranold and U. Lembke

Synopsis

The treatment and analysis of SAXS data are reviewed with specific concern for glass science. The methods developed are illustrated by SAXS and ASAXS scattering results obtained from optical filter glass, glass produced by the sol-gel technique, optical colourless glass inclining to opalescence, porous glass and single-phase phosphate glass.

J. Appl. Cryst. (1997). 30, 1056 - 1064

Phase Formation Kinetics in a Glass Ceramic Studied by Small-Angle Scattering of X-rays and Neutrons and by Visible-Light Scattering

U. Lembke, R. Brückner, R. Kranold and Th. Höche

Synopsis

The primary phase formation in an MgO-Al₂O₃-SiO₂ base glass for glass ceramics was investigated by combining different small-angle scattering techniques. The effect of TiO₂ and ZrO₂ as nucleating agents on the first stage of crystallization was clarified using contrast variation.

J. Appl. Cryst. (1997). 30, 1065 - 1074

Characterization of Hexagonal and Lamellar Mesoporous Silicas, Aluminosilicates and Gallosilicates by Small-Angle X-ray Scattering

G. Van den Bossche, R. Sobry, F. Fontaine, J.-M. Clacens and Z. Gabelica

Synopsis

Small-angle X-ray scattering was used to characterize various mesoporous silicas, aluminosilicates and gallosilicates.

J. Appl. Cryst. (1997). 30, 1075 - 1083

Small-Angle X-ray Scattering and Small-Angle Neutron Scattering Studies of Liquid-Crystalline Halato(semi)telechelic Polymers

R. Sobry, G. Van den Bossche, F. Fontaine, J.-F. Gohy and R. Jérome

Synopsis

Liquid-crystalline halato(semi)telechelic polymers have been studied using small-angle X-ray scattering and small-angle neutron scattering

J. Appl. Cryst. (1997). 30, 1084 - 1095

Studies of Structure and Morphology Development During the Heat-Draw Process of Nylon 66 Fiber by Synchrotron X-ray Diffraction and Scattering Techniques

B. S. Hsiao, A. D. Kennedy, R. A. Leach, B. Chu and P. Harney

Synopsis

The development of structure and morphology during the heat-draw process of a nylon 66 fiber was investigated by two-dimensional WAXD and SAXS methods using synchrotron radiation. The results indicate that a premelting process precedes the Brill transition during the chosen processes.

J. Appl. Cryst. (1997). 30, 1096 - 1104

Glancing-Angle Neutron Diffraction from Smectic C Liquid-Crystal Surfaces

P. L. Phillips, R. M. Richardson, R. Cubitt and S. D. Haslam

Synopsis

Glancing-angle neutron diffraction has been used to study the variation in smectic layer tilt in high- and low-pretilt smectic C cells with distance from the surface.

J. Appl. Cryst. (1997). 30, 1105 - 1111

Spinodal Decomposition in Bicontinuous Microemulsions Studied by Ultra-Small-Angle Time-Resolved Light Scattering

F. Mallamace, N. Micali and S.-H. Chen

Synopsis

Time-resolved small-angle light scattering was used to study phase separation phenomena of the water-octane-tetraethylene glycol monodecyl ether microemulsion system.

J. Appl. Cryst. (1997). 30, 1112 - 1124

Prediction of Hydrodynamic Parameters of Biopolymers from Small-Angle Scattering Data

H. Durchschlag and P. Zipper

Synopsis

Structural parameters of biopolymers derived from small-angle scattering were used to calculate and estimate hydrodynamic parameters. The validity of several approaches was tested with different types of molecules.

J. Appl. Cryst. (1997). 30, 1125 - 1131

Localization of Proteins and tRNA Molecules in the 70S Ribosome of the Escherichia coli Bacteria with Polarized Neutron Scattering

R. Willumeit, N. Burkhardt, R. Jünemann, J. Wadzack, K. H. Nierhaus and H. B. Stuhrmann

Synopsis

Questions of biological structure research that cannot be solved because of insufficient contrast conditions could be answered by spin contrast variation.

J. Appl. Cryst. (1997). 30, 1132 - 1139

Fully Numerical Procedure for Anisotropic Small-Angle Neutron Scattering Modelling and Data Evaluation

P. Strunz and A. Wiedenmann

Synopsis

A numerical approach to the evaluation of two-dimensional small-angle neutron scattering data which includes interparticle-interference and multiple-scattering effects is described.

J. Appl. Cryst. (1997). 30, 1140 - 1147

SANS at Pulsed Neutron Sources: Present and Future Prospects

R. K. Heenan, J. Penfold and S. M. King

Synopsis

The present and future prospects of small-angle neutron scattering at pulsed neutron sources are reviewed.

SHORT COMMUNICATIONS

J. Appl. Cryst. (1997). 30, 1148 - 1149

Observation of antiphase domain structure in chlorapatite

X.-M. Yang

Synopsis

The antiphase domains can be explained in terms of the ordering of the Cl ion in the channels of the chlorapatite structure. The displacement vector of the domain was found to be (1/2)[010].

J. Appl. Cryst. (1997). 30, 1150 - 1151

Measurement of a bent-crystal rocking curve with oscillations

I. Uschmann, C. Malgrange and E. Förster

Synopsis

Experimental observations of the fine structure of a bent-crystal rocking curve, made with a double-crystal diffractometer, are reported.

J. Appl. Cryst. (1997). 30, 1152 - 1155

Isomorphic relationship between 1,2,4,5-tetrachlorobenzene and 1,2,4,5-tetrabromobenzene

F. Michaud, P. Negrier, Y. Haget, J.-M. Leger, C. Courseille, M. A. Cuevas Diarte and H. A. J. Oonk

Synopsis

X-ray powder diffraction on mixed crystalline samples has been performed to determine which of the two forms of l,2,4,5-tetrabromobenzene (TeBB) is isomorphous with the room temperature form of l,2,4,5-tetrachlorobenzene (TeCB). It is found that beta TeCB is isomorphous in the strictest sense (i.e. capable of giving a continuous series of mixed crystals) with the gamma form of TeBB.

J. Appl. Cryst. (1997). 30, 1156 - 1158

Phases, lattice parameters and thermal expansion of HoNi_5-xAl_x, 4 >= x >= 0

B. Grzeta, B. Sorgic and Z. Blazina

Synopsis

An X-ray powder diffraction study of the structural characteristics and thermal expansion between room temperature and 873 K is reported for the system HoNi_5-xAl_x, 4 >= x >= 0.

J. Appl. Cryst. (1997). 30, 1159

Ba₆CoNb₉O₃₀ and Ba₆FeNb₉O₃₀: two new tungsten-bronze-type ferroelectrics. Centrosymmetry of Ba_5.2K_0.8U_2.4Nb_7.6O₃₀ at 300 K. Erratum

M. C. Foster, G. R. Brown, R. M. Nielson and S. C. Abrahams

Synopsis

Correction to J. Appl. Cryst. 30, 495 - 501.

J. Appl. Cryst. (1997). 30, 1159

Two-dimensional small-angle X-ray scattering investigation of stretched borosilicate glasses. Erratum

S. Polizzi, P. Riello, G. Fagherazzi, M. Bark and N. F. Borrelli

Synopsis

Correction to J. Appl. Cryst. 30, 487 - 494.

COMPUTER PROGRAMS

J. Appl. Cryst. (1997). 30, 1160 - 1161

ALIGN: a program to superimpose protein coordinates, accounting for insertions and deletions

G. E. Cohen

Synopsis

The program ALIGN determines the transformation to superimpose structurally homologous protein domains. The results are expressed in terms of the rotation and translation necessary to effect the transformation.

LABORATORY NOTES

J. Appl. Cryst. (1997). 30, 1162 - 1164

A new single-crystal mounting technique for low-background high-temperature X-ray diffraction

J. Schreuer, A. Baumgarte and W. Steurer

Synopsis

A new single-crystal mounting technique for high-temperature X-ray diffraction up to 1700 K is briefly described. The major advantage of the method is the very low background, because the sample is clamped by thin microcrystalline fibres without using any glue or cement.

J. Appl. Cryst. (1997). 30, 1165 - 1166

A helium beam path for an imaging-plate detector system

M. A. Esterman, S. Scheidegger, H. Reifler and W. Steurer

Synopsis

A helium beam path for the marresearch imaging-plate detector system is described.

FAST COMMUNICATIONS

J. Appl. Cryst. (1997). 30, 1167 - 1172

Using a structure envelope to facilitate structure solution from powder diffraction data

S. Brenner, L. B. McCusker and C. Baerlocher

Synopsis

A periodic nodal surface that partitions a unit cell into regions of high and low electron density can be calculated from a few strong, low-index reflections. This `structure envelope' can then be used to facilitate structure solution from powder diffraction data.

J. Appl. Cryst. (1997). 30, 1173

Crystallographers

J. Appl. Cryst. (1997). 30, 1173

Notes and News

J. Appl. Cryst. (1997). 30, 1173 - 1175

International Union of Crystallography. Prices of IUCr journals

J. Appl. Cryst. (1997). 30, 1175

Books Received

J. Appl. Cryst. (1997). 30, 1176

Subject index

J. Appl. Cryst. (1997). 30, 1182

Author index

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