Relativistic X-ray Elastic Scattering Factors for He–Ar from Dirac–Hartree–Fock Wave Functions

Relativisitic X-ray and electron scattering factors for first- and second-row atoms and ions are tabulated. The present results are based on multiconfiguration Dirac–Hartree–Fock calculations which have the correct non-relativistic limit and will allow relativistic contributions to the scattering factors to be extracted properly.

Improved Structure Refinement Through Maximum Likelihood

Maximum-likelihood refinement can improve a protein structure more than twice as much as least-squares refinement.

Observation of Phase Change of X-ray Polarizability in Rocking Curves

By measurement of the change of asymmetry of the transmitted rocking curves for GaAs 200 diffraction near K-absorption edges, the phase change of the structure factors was examined.

The Phase Problem in Structure Analysis and its One-Dimensional Solution

A new approach to the one-dimensional solution of the phase problem in diffraction is given, introducing periodic Fourier transforms of shift functions.

Maximal Subgroups of Magnetic Space Groups and Subperiodic Groups

A method is given for the derivation of the maximal subgroups of magnetic space groups and subperiodic groups.

Dynamical Effects of High-Energy Diffraction in Non-centrosymmetric Sphalerite, ZnS

Dynamical effects in high-energy electron diffraction were observed in sphalerite, ZnS. The structure factors of lower angle were measured.

Elimination of Extinction Effects by Extrapolation to Zero Wavelength

The practicality of extrapolating multiple-wavelength single- crystal intensity measurements to zero wavelength for extinc- tion-correction purposes is investigated.

The Electrostatic Contribution to the Forward-Scattering Potential at aSpace Charge Layer in High-Energy Electron Diffraction. I. Theory Neglecting the Effects of Fringing Fields

Expressions for the electrostatic potential at an interfacial space charge layer are determined using classical electrostatics, with particular reference to the use of phase-contrast techniques in transmission electron microscopy for characterizing such layers. Both the sensitivity of the potential to the detailed form of the charge distribution and the effect of the internal electric field on the strain within the material are discussed.

Derivation of the Joint Probability Distribution of Structure-Factor Components Without Assuming Independent Atoms: Relation to the Sparse-Density Principle

A number of equations based on the sparse-density principle are derived, along with the corresponding j.p.d.'s, and the effect of the assumption of independent atoms is investigated.

Electron Statistical Dynamical Diffuse Scattering in Crystals Containing Short-Range-Order Point Defects

A formal statistical dynamical theory is developed to calculate Bragg and diffuse scattering produced by short-range order (SRO) in a distorted crystal structure with consideration of atomic thermal vibrations. A rigorous proof is given to show the inclusion of a complex potential in the dynamical calculation automatically recovers the contributions made by the high-order diffuse scattering, although the calculation is done using the equation derived under the distorted-wave Born approximation.

Diffraction-Line Broadening due to Strain Fields in Materials; Fundamental Aspects and Methods of Analysis

Diffraction-line broadening due to strain fields in materials is discussed. A generally applicable model for distributions of lattice defects and their distortion fields is presented.

Evaluation of Sternheimer Nuclear Quadrupole Shielding Functions and their Application to the Determination of the ⁵⁷Fe^m Nuclear Quadrupole Moment from X-ray-Determined Charge Densities

Values for the electric field gradient at the iron nucleus from the X-ray charge density and from Mössbauer spectroscopy are compared to obtain the ⁵⁷Fe^m nuclear quadrupole moment. Sternheimer shielding and antishielding factors are derived and used to account for core-polarization effects.

The Use of Discrete Hilbert Transforms in Phase Extension and Improvement

A model-independent procedure for phase extension and improvement, based on the discrete Hilbert transforms, is presented.

Optical Activity of Crystalline Glutamic Acids

As the first study on gyro-optical properties of amino acids, temperature dependences of gyration tensor components of L- and D-glutamic acids were measured using the high-accuracy universal polarimeter (HAUP).

Atomic Dispacement Parameter Nomenclature. Report of a Subcommittee on Atomic Displacement Parameter Nomenclature

The nomenclature and symbols to be used in discussing the parameters that describe dynamic and static displacements of atoms in crystals, as determined from Bragg diffraction data, are considered in detail. The emphasis is on parameters derived from the Gaussian approximation.

Combined molecular replacement

The combined molecular replacement protocol performs a limited six-dimensional search to find molecular replacement solutions.

Comments on Crystal Properties via Group Theory by A. S. Nowick, Cambridge University Press, 1995

Nowick's book is criticized for a mis-statement in its preface about previous work on group theory.

New Editor-in-Chief of IUCr journals