(IUCr) Contents for Acta Crystallographica Section A Vol. 56 Part 6 (November 2000)

Acta Cryst. (2000). A56, 511-518 [ doi:10.1107/S0108767300007522 ]

Quasi-dynamical electron diffraction - a kinematic type of expression for the dynamical diffracted-beam amplitudes

L.-M. Peng

Synopsis: A kinematic type of expression is derived for the dynamical diffracted-beam amplitudes and its validity is illustrated for thin films of GaAs and Au.

Online November 2000

Acta Cryst. (2000). A56, 519-524 [ doi:10.1107/S0108767300007558 ]

Debye-Waller factors of compounds with the caesium chloride structure

H. X. Gao and L.-M. Peng

Synopsis: Temperature-dependent Debye-Waller B factors have been obtained for five compounds with the caesium chloride structure.

Online November 2000

Acta Cryst. (2000). A56, 525-528 [ doi:10.1107/S0108767300009119 ]

A hybrid minimal principle for the crystallographic phase problem

X. Liu and W.-P. Su

Synopsis: The phase problem is formulated as the minimization of a cost function with respect to the atomic coordinates. The cost function involves both the magnitude and phase of the calculated structure factors. Structures undergoing trial calculations include hexadecaisoleucinomycin.

Online November 2000

Acta Cryst. (2000). A56, 529-535 [ doi:10.1107/S0108767300009405 ]

Low-resolution direct phase determination in protein electron crystallography - breaking globular constraints

D. L. Dorset

Synopsis: False low-resolution crystallographic phases for a macromolecule generated under globular density constraints can be corrected via error-correcting codes.

Online November 2000

Acta Cryst. (2000). A56, 536-539 [ doi:10.1107/S0108767300009740 ]

A model for diffraction from MCM-41 materials

Z. Tun and P. C. Mason

Synopsis: A model involving only a small number of parameters provides a convenient way of interpreting diffraction patterns from MCM-41 materials. Each parameter of the model has a clear physical meaning, and this approach is clearly superior to extracting pore structure information by fitting Gaussians to an observed diffraction pattern.

Online November 2000

Acta Cryst. (2000). A56, 540-548 [ doi:10.1107/S010876730000996X ]

The statistical kinematical theory of X-ray diffraction as applied to reciprocal-space mapping

Y. I. Nesterets and V. I. Punegov

Synopsis: The statistical kinematical X-ray diffraction theory is developed to describe reciprocal-space maps from deformed crystals with structural defects.

Online November 2000

Acta Cryst. (2000). A56, 549-553 [ doi:10.1107/S0108767300010205 ]

The crystallite size-disorder relationship based on the spiral paracrystal

J. L. Eads and R. P. Millane

Synopsis: A simple model of the crystallite size-disorder relationship for paracrystalline materials (the $\alpha^{*}$ rule) based on the spiral paracrystal is described. Simulation results based on this model are presented.

Online November 2000

Acta Cryst. (2000). A56, 554-561 [ doi:10.1107/S0108767300008849 ]

Resolution of the phase-ambiguity problem in the centrosymmetric $P \bar{1}$ space group by Monte Carlo methods

M. Delarue

Synopsis: Simulated-annealing Monte Carlo methods in the multistart mode were successful in overcoming the phase-ambiguity problem in space group $P\bar{1}$ ; for the small protein rubredoxin. This involved minimization of an energy function derived from the Sayre equation and monitoring the Terwilliger criterion characterizing the roughness of the resulting maps.

Online November 2000

Acta Cryst. (2000). A56, 562-574 [ doi:10.1107/S0108767300010242 ]

General formalism for phase combination and phase refinement: a statistical thermodynamics approach in reciprocal space

M. Delarue and H. Orland

Synopsis: Mean-field optimization has been used to recast in a single formalism the problem of phase optimization using an arbitrary energy function in the presence of an experimentally determined phase probability function; this leads to the definition of a generalized figure of merit. Thermodynamic considerations lead to a new discussion of how to determine the relative weights in phase refinement and suggest that the free energy might be a better refinement target than maximum likelihood.

Online November 2000

Acta Cryst. (2000). A56, 575-584 [ doi:10.1107/S0108767300010254 ]

Topological analyses of cuprite, Cu₂O, using high-energy synchrotron-radiation data

T. Lippmann and J. R. Schneider

Synopsis: Topological analyses and space partitioning were performed on high-energy synchrotron-radiation data from Cu₂O.

Online November 2000

Acta Cryst. (2000). A56, 585-591 [ doi:10.1107/S0108767300011405 ]

The experimental charge-density approach in the evaluation of intermolecular interactions. Application of a new module of the XD programming package to several solids including a pentapeptide

Y. A. Abramov, A. Volkov, G. Wu and P. Coppens

Synopsis: A new module interfaced to the XD programming package has been used in the evaluation of intermolecular interactions and lattice energies of crystals of p-nitroaniline, L-asparagine monohydrate and the pentapeptide Boc-Gln-Iva-Hyp-Ala-Phol. Comparison with ab initio supermolecular calculations at the HF, DFT and MP2 levels and with HF and DFT periodic crystal calculations shows agreement and discrepancies, the nature of which is discussed.

Online November 2000

Acta Cryst. (2000). A56, 592-595 [ doi:10.1107/S0108767300011417 ]

Solving crystal structures from two-wavelength X-ray powder diffraction data - breaking the phase ambiguity in the noncentrosymmetric case

Y. X. Gu, Y. D. Liu, Q. Hao and H. F. Fan

Synopsis: The direct method of breaking phase ambiguity is applied in solving noncentrosymmetric crystal structures from two-wavelength powder diffraction data.

Online November 2000

Acta Cryst. (2000). A56, 596-605 [ doi:10.1107/S010876730001031X ]

On possible extensions of X-ray crystallography through diffraction-pattern oversampling

J. Miao and D. Sayre

Synopsis: Sampling the diffraction pattern of a finite specimen at a spacing finer than the Nyquist spacing (the inverse of the size of the diffracting specimen) corresponds to surrounding the electron density of the specimen with a no-density region. This no-density region can be used to retrieve the phase information directly from the diffraction pattern of (a) a small perfect or imperfect crystal or (b) a repeated motif without orientational regularity or (c) an unrepeated motif, such as an amorphous glass, a single molecule or a single biological cell.

Online November 2000

short communications

Acta Cryst. (2000). A56, 606-608 [ doi:10.1107/S0108767300011314 ]

New developments of the TWIN algorithm for phase extension and refinement in disordered supramolecular structures

K. Bethanis, P. Tzamalis, A. Hountas, G. Tsoucaris, A. Kokkinou and D. Mentzafos

Synopsis: Specific problems in disordered supramolecular structures are solved by a new development of the TWIN algorithm, through the calculation of the `super-resolution wave function'.

Online November 2000

international union of crystallography

Acta Cryst. (2000). A56, 609-642 [ doi:10.1107/S0108767300012873 ]

Report of the Executive Committee for 1999

Online November 2000

Acta Cryst. (2000). A56, 643-644 [ doi:10.1107/S0108767300013945 ]

Prices of IUCr journals

Online November 2000

Acta Crystallographica Section A

Foundations of Crystallography

Volume 56, Part 6 (November 2000)

research papers

Quasi-dynamical electron diffraction - a kinematic type of expression for the dynamical diffracted-beam amplitudes

L.-M. Peng

Debye-Waller factors of compounds with the caesium chloride structure

H. X. Gao and L.-M. Peng

A hybrid minimal principle for the crystallographic phase problem

X. Liu and W.-P. Su

Low-resolution direct phase determination in protein electron crystallography - breaking globular constraints

D. L. Dorset

A model for diffraction from MCM-41 materials

Z. Tun and P. C. Mason

The statistical kinematical theory of X-ray diffraction as applied to reciprocal-space mapping

Y. I. Nesterets and V. I. Punegov

The crystallite size-disorder relationship based on the spiral paracrystal

J. L. Eads and R. P. Millane

Resolution of the phase-ambiguity problem in the centrosymmetric $P \bar{1}$ space group by Monte Carlo methods

M. Delarue

General formalism for phase combination and phase refinement: a statistical thermodynamics approach in reciprocal space

M. Delarue and H. Orland

Topological analyses of cuprite, Cu₂O, using high-energy synchrotron-radiation data

T. Lippmann and J. R. Schneider

The experimental charge-density approach in the evaluation of intermolecular interactions. Application of a new module of the XD programming package to several solids including a pentapeptide

Y. A. Abramov, A. Volkov, G. Wu and P. Coppens

Solving crystal structures from two-wavelength X-ray powder diffraction data - breaking the phase ambiguity in the noncentrosymmetric case

Y. X. Gu, Y. D. Liu, Q. Hao and H. F. Fan

On possible extensions of X-ray crystallography through diffraction-pattern oversampling

J. Miao and D. Sayre

short communications

New developments of the TWIN algorithm for phase extension and refinement in disordered supramolecular structures

K. Bethanis, P. Tzamalis, A. Hountas, G. Tsoucaris, A. Kokkinou and D. Mentzafos

international union of crystallography

Report of the Executive Committee for 1999

Prices of IUCr journals


	Cover illustration: Unit cell of a self-intersecting minimal surface with symmetry I432. The surface subdivides R³ into two congruent three-periodic mutually interpenetrating labyrinths with symmetry P4₂32. Lines of self-intersection are marked in red. See Koch [Acta Cryst. (2000), A56, 15-23].

Acta Crystallographica Section A

Foundations of Crystallography

Volume 56, Part 6 (November 2000)

research papers

Quasi-dynamical electron diffraction - a kinematic type of expression for the dynamical diffracted-beam amplitudes

L.-M. Peng

Debye-Waller factors of compounds with the caesium chloride structure

H. X. Gao and L.-M. Peng

A hybrid minimal principle for the crystallographic phase problem

X. Liu and W.-P. Su

Low-resolution direct phase determination in protein electron crystallography - breaking globular constraints

D. L. Dorset

A model for diffraction from MCM-41 materials

Z. Tun and P. C. Mason

The statistical kinematical theory of X-ray diffraction as applied to reciprocal-space mapping

Y. I. Nesterets and V. I. Punegov

The crystallite size-disorder relationship based on the spiral paracrystal

J. L. Eads and R. P. Millane

Resolution of the phase-ambiguity problem in the centrosymmetric space group by Monte Carlo methods

M. Delarue

General formalism for phase combination and phase refinement: a statistical thermodynamics approach in reciprocal space

M. Delarue and H. Orland

Topological analyses of cuprite, Cu2O, using high-energy synchrotron-radiation data

T. Lippmann and J. R. Schneider

The experimental charge-density approach in the evaluation of intermolecular interactions. Application of a new module of the XD programming package to several solids including a pentapeptide

Y. A. Abramov, A. Volkov, G. Wu and P. Coppens

Solving crystal structures from two-wavelength X-ray powder diffraction data - breaking the phase ambiguity in the noncentrosymmetric case

Y. X. Gu, Y. D. Liu, Q. Hao and H. F. Fan

On possible extensions of X-ray crystallography through diffraction-pattern oversampling

J. Miao and D. Sayre

short communications

New developments of the TWIN algorithm for phase extension and refinement in disordered supramolecular structures

K. Bethanis, P. Tzamalis, A. Hountas, G. Tsoucaris, A. Kokkinou and D. Mentzafos

international union of crystallography

Report of the Executive Committee for 1999

Prices of IUCr journals

Resolution of the phase-ambiguity problem in the centrosymmetric $P \bar{1}$ space group by Monte Carlo methods

Topological analyses of cuprite, Cu₂O, using high-energy synchrotron-radiation data