Foundations of Crystallography

 

Acta Cryst. (1999). A55, 401-412  [ doi:10.1107/S0108767398010368 ]

The morphology of quasicrystals, incommensurate composite crystals and modulated crystals derived from the broken-bond model

S. van Smaalen

Synopsis: A model for the surface free energy is proposed for incommensurate intergrowth compounds. Facetting of this type of aperiodic crystals is thus explained, and it is predicted that main facets common to the subsystems will have the highest morphological importance.

Online May 1999

 

Acta Cryst. (1999). A55, 413-422  [ doi:10.1107/S0108767398010514 ]

Theory of moiré fringes on X-ray diffraction topographs of bicrystals

M. Ohler and J. Härtwig

Synopsis: The properties of moiré fringes on X-ray diffraction topographs of bicrystals are derived from the dynamical theory of X-ray diffraction and discussed for experimentally relevant cases.

Online May 1999

 

Acta Cryst. (1999). A55, 423-432  [ doi:10.1107/S0108767398010794 ]

X-ray diffraction moiré topography as a means to reconstruct relative displacement fields in weakly deformed bicrystals

M. Ohler, S. Köhler and J. Härtwig

Synopsis: A new method to analyse moiré fringes allows the relative displacement field between the two parts of bicrystals to be reconstructed with a strain sensitivity of 10^-6 to 10^-8.

Online May 1999

 

Acta Cryst. (1999). A55, 433-447  [ doi:10.1107/S010876739801071X ]

Small-angle scattering by dislocations

R. Thomson, L. E. Levine and G. G. Long

Synopsis: It is shown that the small-angle scattering of X-rays or neutrons by dislocations within a deformed metal, which are partially ordered into wall-like structures, is characterized by several factors. Principally, these are associated with: (i) a single dislocation or dipole; (ii) the dislocation configuration in the plane of the wall; and (iii) the distribution of dislocations across the wall thickness.

Online May 1999

 

Acta Cryst. (1999). A55, 448-456  [ doi:10.1107/S0108767398010836 ]

Direct methods in protein electron crystallography - beef liver catalase in its fully hydrated form at room temperature

D. L. Dorset and C. J. Gilmore

Synopsis: A direct analyis of the hydrated catalase crystal structure at room temperature is consistent with earlier studies of frozen hydrated samples by electron microscopy.

Online May 1999

 

Acta Cryst. (1999). A55, 457-465  [ doi:10.1107/S0108767398012185 ]

Three-wave grazing-incidence X-ray diffraction from thin crystal surface layers: determination of triplet phase invariants

Y. P. Stetsko and S.-L. Chang

Synopsis: Numerical calculation of the angular and spectral distributions of the intensities of the specularly diffracted waves in the case of three-wave grazing-incidence X-ray diffraction is carried out using the dynamical theory. A method of determining the value of the triplet phase invariant for thin crystal surface layers is also developed.

Online May 1999

 

Acta Cryst. (1999). A55, 466-470  [ doi:10.1107/S0108767398014949 ]

About new applications of parametric X-radiation for crystallography

I. D. Feranchuk and A. Ulyanenkov

Synopsis: A theoretical analysis of the parametric X-radiation (PXR) produced by the nonrelativistic electrons in an X-ray tube with a monocrystalline anode is presented.

Online May 1999

 

Acta Cryst. (1999). A55, 471-479  [ doi:10.1107/S0108767398012604 ]

Quantitative zone-axis convergent-beam electron diffraction (CBED) studies of metals. I. Structure-factor measurements

M. Saunders, A. G. Fox and P. A. Midgley

Synopsis: The quantitative zone-axis CBED technique ZAPMATCH is applied to low-order structure-factor measurements in nickel and copper in an attempt to resolve the debate regarding the accuracy of various experimental methods and theory calculations that have previously been applied to these materials. The extension of ZAPMATCH to the study of thermal diffuse scattering effects is also considered.

Online May 1999

 

Acta Cryst. (1999). A55, 480-488  [ doi:10.1107/S0108767398016316 ]

Quantitative zone-axis convergent-beam electron diffraction (CBED) studies of metals. II. Debye-Waller-factor measurements

M. Saunders, A. G. Fox and P. A. Midgley

Synopsis: The possibility of using the ZAPMATCH quantitative CBED pattern-matching technique to measure Debye-Waller factors accurately is investigated. The application of this approach to nickel and copper <110> zone-axis patterns is discussed.

Online May 1999

 

Acta Cryst. (1999). A55, 489-499  [ doi:10.1107/S0108767398013324 ]

X-ray phase determination by the principle of minimum charge

V. Elser

Synopsis: The minimum value of the electron density in the unit cell is proposed as an objective function for phase determination. An algorithm for maximizing this objective function, based on linear programming, finds the correct phases in numerical experiments with simulated crystalline and quasicrystalline structures.

Online May 1999

 

Acta Cryst. (1999). A55, 500-507  [ doi:10.1107/S0108767398013543 ]

The use of multiple-scattering data to enhance small-angle neutron scattering experiments

T. M. Sabine and W. K. Bertram

Synopsis: It is shown that SANS patterns from specimens of different thicknesses but otherwise identical not only provide information on the shape and size of the scattering entity but also give absolute values of the scattering contrast between particles responsible for SANS and the matrix. No separate calibration of the incident beam is required.

Online May 1999

 

Acta Cryst. (1999). A55, 508-511  [ doi:10.1107/S0108767398013841 ]

Quasiperiodic patterns generated by mixing lattices derived from a dodecahedral star and an icosahedral star

T. Soma and Y. Watanabe

Synopsis: A mixing of lattices derived from a dodecahedral star and an icosahedral star is considered giving a 16  ×  16 matrix for the cut-and-project method of generating 3D quasiperiodic patterns.

Online May 1999

 

Acta Cryst. (1999). A55, 512-524  [ doi:10.1107/S0108767398014792 ]

The joint probability distribution function of structure factors with rational indices. IV. The P1 case

C. Giacovazzo, D. Siliqi and C. Fernández-Castaño

Synopsis: Joint probability distribution functions of structure factors with rational indices are derived in P1. Phase relationships are obtained.

Online May 1999

 

Acta Cryst. (1999). A55, 525-532  [ doi:10.1107/S0108767398014809 ]

The joint probability distribution function of structure factors with rational indices. V. The estimates

C. Giacovazzo, D. Siliqi, C. Fernández-Castaño and G. Comunale

Synopsis: Probabilistic formulae for estimating structure factors of half-integral index reflections are given and experimental tests are performed.

Online May 1999

 

Acta Cryst. (1999). A55, 533-542  [ doi:10.1107/S0108767398014950 ]

Moiré patterns in electron microscopy with atomic focuser crystals

J. M. Cowley, N. Ooi and R. E. Dunin-Borkowski

Synopsis: The sharply peaked maxima of electron intensity formed at the exit face of a thin atomic focuser crystal may be used to derive the structure of a thin specimen crystal with a resolution of better than 0.04 nm.

Online May 1999

 

Acta Cryst. (1999). A55, 543-557  [ doi:10.1107/S0108767398015037 ]

On the geometry of a modern imaging diffractometer

W. A. Paciorek, M. Meyer and G. Chapuis

Synopsis: A method is proposed to calibrate all the relevant instrumental parameters of a multicircle diffractometer equipped with an area detector.

Online May 1999

 

Acta Cryst. (1999). A55, 558-560  [ doi:10.1107/S010876739801126X ]

Positive-definite conditions of elastic constants of two-dimensional quasicrystals with noncrystallographic symmetries

J. Wang, R. Zhang, D.-H. Ding and R. Wang

Synopsis: The positive-definite conditions of the elastic constants of two-dimensional quasicrystals with non-crystallographic symmetries have been derived.

Online May 1999

 

Acta Cryst. (1999). A55, 561-563  [ doi:10.1107/S0108767399000173 ]

A simple view of the spherical wave in dynamical theory

J. P. Guigay

Synopsis: The well known spherical-wave results are obtained by a simple and direct calculation.

Online May 1999

 

Acta Cryst. (1999). A55, 564  [ doi:10.1107/S0108767399003232 ]

Solving crystal structures without Fourier mapping. I. Centrosymmetric case. Erratum

K. Pilz and K. F. Fischer

Synopsis: Erratum to Acta Cryst. (1998), A54, 273-282.

Online May 1999

 

Acta Cryst. (1999). A55, 565-600  [ doi:10.1107/S0108767399004237 ]

International Union of Crystallography
> Report of the Executive Committee for 1997

Online May 1999