(IUCr) Contents for Acta Crystallographica Section A Vol. 60 Part 3 (May 2004)

Acta Cryst. (2004). A60, 201-203 [ doi:10.1107/S0108767304003654 ]

A strict solution for the optimal superimposition of protein structures

C. Chen and Q. Li

Synopsis: Existing methods for the optimal superimposition of two protein molecules are based on the precondition that the centroids of the vector sets of their atomic coordinates are coincident. This is obviously not strict in the mathematical sense. The theorem presented in this paper is a strict solution for this problem in the mathematical sense.

Online 22 April 2004

Acta Cryst. (2004). A60, 204-208 [ doi:10.1107/S0108767304004246 ]

A comparison between experimental and theoretical aspherical-atom scattering factors for charge-density refinement of large molecules

V. Pichon-Pesme, C. Jelsch, B. Guillot and C. Lecomte

Synopsis: Two databases of multipoles describing the electron density of the polypeptide main chain are compared.

Online 22 April 2004

Acta Cryst. (2004). A60, 209-213 [ doi:10.1107/S0108767304004714 ]

X-ray multiple-wave coherent interaction in a quasi-two-dimensional material NbSe₂-2H

C.-H. Du, M.-T. Tang, Y. P. Stetsko, Y.-R. Lee, C.-W. Wang, C.-W. Cheng and S.-L. Chang

Synopsis: The first observation of X-ray multiple-wave interaction in an incommensurate charge-density-wave (CDW) modulated structure at low temperatures is reported for an example of a quasi-two-dimensional material, NbSe₂-2H.

Online 22 April 2004

Acta Cryst. (2004). A60, 214-219 [ doi:10.1107/S0108767304002739 ]

On the equivalence between a commonly used correlation coefficient and a least-squares function

D. C. Jamrog, Y. Zhang and G. N. Phillips

Synopsis: It is established that the set of global maximizers of a commonly used correlation coefficient are also global minimizers of a least-squares function.

Online 22 April 2004

Acta Cryst. (2004). A60, 220-232 [ doi:10.1107/S0108767304006695 ]

Twinning by reticular pseudo-merohedry in trigonal, tetragonal and hexagonal crystals

H. Grimmer and K. Kunze

Synopsis: Twin laws by (reticular) pseudo-merohedry are investigated for which the obliquity [delta] vanishes for an appropriate value of the axial ratio c/a. For arbitrary values of c/a, it is shown that [delta] is related to the deformation parameter [epsilon] introduced by Bonnet & Durand [Philos. Mag. (1975), 32, 997-1006]. Furthermore, tan [delta] is a product of two factors: one describes the dependency on the lattice parameters, the other the effect of the lattice misorientation.

Online 22 April 2004

Acta Cryst. (2004). A60, 233-238 [ doi:10.1107/S010876730400683X ]

Locating heavy atoms by integrating direct methods and SIR techniques

C. Giacovazzo, M. Moustiakimov, D. Siliqi and A. Pifferi

Synopsis: The joint probability distribution method has been applied to locate heavy atoms in the isomorphous replacement method.

Online 22 April 2004

Acta Cryst. (2004). A60, 239-245 [ doi:10.1107/S0108767304005513 ]

Exceptional properties of some sphere packings in the general position of P6₂22

E. Koch and H. Sowa

Synopsis: Three types of sphere packing with remarkable properties are described. They show that from the crystallographic point of view in exceptional cases the usual definition of sphere-packing types based on graph-theoretical criteria may be not sufficient.

Online 22 April 2004

Acta Cryst. (2004). A60, 246-249 [ doi:10.1107/S0108767304007275 ]

Minimal densities of cubic sphere-packing types

W. Fischer

Synopsis: Minimal sphere-packing densities and sample coordinates are presented for all 199 types of homogeneous sphere packings with cubic symmetry.

Online 22 April 2004

Acta Cryst. (2004). A60, 250-256 [ doi:10.1107/S0108767304007688 ]

Atomic displacement parameters and anisotropic thermal ellipsoid lengths and angles

M. J. Kronenburg

Synopsis: The moments of the probability distribution of n-dimensional anisotropic thermal ellipsoids are provided as functions of dimension n. For specific dimensions n = 2 and n = 3, new formulas are presented for the semi-axis lengths and rotation angles of the thermal ellipsoids.

Online 22 April 2004

Acta Cryst. (2004). A60, 257-262 [ doi:10.1107/S0108767304007585 ]

Crystal structures and cellular automata

S. V. Krivovichev

Synopsis: Cellular automata are used to model the topology of structures consisting of frameworks based upon fundamental building blocks.

Online 22 April 2004

Acta Cryst. (2004). A60, 263-277 [ doi:10.1107/S010876730400772X ]

The structure of the cubic coincident site lattice rotation group

B. W. Reed, R. W. Minich, R. E. Rudd and M. Kumar

Synopsis: The mathematical relationships among rotations producing coincident site lattices are developed in terms of intuitively understandable algebraic and topological models. Examples demonstrate applications in grain-boundary engineering and in the statistical descriptions of grain-boundary networks.

Online 22 April 2004

short communications

Acta Cryst. (2004). A60, 278-280 [ doi:10.1107/S0108767304004842 ]

A theorem on the fullerenes with no adjacent pentagons

Y. L. Voytekhovsky and D. G. Stepenshchikov

Synopsis: The theorem that a fullerene C_n with any even n 70 and no adjacent pentagons exists is proved.

Online 22 April 2004

Acta Cryst. (2004). A60, 281-282 [ doi:10.1107/S0108767304005884 ]

Polarization factors in the symmetrical case of three-wave diffraction

S. Sheludko

Synopsis: The symmetrical case of multiple diffraction, where a triplet of the diffraction vectors forms an isosceles triangle, is considered. A simple trigonometric form is obtained for the polarization factor by treating separately the variables for spectral-dependent and spectral-independent contributions.

Online 22 April 2004

Acta Crystallographica Section A

Foundations of Crystallography

Volume 60, Part 3 (May 2004)

research papers

A strict solution for the optimal superimposition of protein structures

C. Chen and Q. Li

A comparison between experimental and theoretical aspherical-atom scattering factors for charge-density refinement of large molecules

V. Pichon-Pesme, C. Jelsch, B. Guillot and C. Lecomte

X-ray multiple-wave coherent interaction in a quasi-two-dimensional material NbSe₂-2H

C.-H. Du, M.-T. Tang, Y. P. Stetsko, Y.-R. Lee, C.-W. Wang, C.-W. Cheng and S.-L. Chang

On the equivalence between a commonly used correlation coefficient and a least-squares function

D. C. Jamrog, Y. Zhang and G. N. Phillips

Twinning by reticular pseudo-merohedry in trigonal, tetragonal and hexagonal crystals

H. Grimmer and K. Kunze

Locating heavy atoms by integrating direct methods and SIR techniques

C. Giacovazzo, M. Moustiakimov, D. Siliqi and A. Pifferi

Exceptional properties of some sphere packings in the general position of P6₂22

E. Koch and H. Sowa

Minimal densities of cubic sphere-packing types

W. Fischer

Atomic displacement parameters and anisotropic thermal ellipsoid lengths and angles

M. J. Kronenburg

Crystal structures and cellular automata

S. V. Krivovichev

The structure of the cubic coincident site lattice rotation group

B. W. Reed, R. W. Minich, R. E. Rudd and M. Kumar

short communications

A theorem on the fullerenes with no adjacent pentagons

Y. L. Voytekhovsky and D. G. Stepenshchikov

Polarization factors in the symmetrical case of three-wave diffraction

S. Sheludko

Acta Crystallographica Section A

Foundations of Crystallography

Volume 60, Part 3 (May 2004)

research papers

A strict solution for the optimal superimposition of protein structures

C. Chen and Q. Li

A comparison between experimental and theoretical aspherical-atom scattering factors for charge-density refinement of large molecules

V. Pichon-Pesme, C. Jelsch, B. Guillot and C. Lecomte

X-ray multiple-wave coherent interaction in a quasi-two-dimensional material NbSe2-2H

C.-H. Du, M.-T. Tang, Y. P. Stetsko, Y.-R. Lee, C.-W. Wang, C.-W. Cheng and S.-L. Chang

On the equivalence between a commonly used correlation coefficient and a least-squares function

D. C. Jamrog, Y. Zhang and G. N. Phillips

Twinning by reticular pseudo-merohedry in trigonal, tetragonal and hexagonal crystals

H. Grimmer and K. Kunze

Locating heavy atoms by integrating direct methods and SIR techniques

C. Giacovazzo, M. Moustiakimov, D. Siliqi and A. Pifferi

Exceptional properties of some sphere packings in the general position of P6222

E. Koch and H. Sowa

Minimal densities of cubic sphere-packing types

W. Fischer

Atomic displacement parameters and anisotropic thermal ellipsoid lengths and angles

M. J. Kronenburg

Crystal structures and cellular automata

S. V. Krivovichev

The structure of the cubic coincident site lattice rotation group

B. W. Reed, R. W. Minich, R. E. Rudd and M. Kumar

short communications

A theorem on the fullerenes with no adjacent pentagons

Y. L. Voytekhovsky and D. G. Stepenshchikov

Polarization factors in the symmetrical case of three-wave diffraction

S. Sheludko

X-ray multiple-wave coherent interaction in a quasi-two-dimensional material NbSe₂-2H

Exceptional properties of some sphere packings in the general position of P6₂22