issue contents

ISSN: 2053-2733

March 2005 issue

Highlighted illustration

Cover illustration: An experimentally derived plot of the Fermi hole mobility function (FHMF) for urea. The FHMF can be interpreted as a potential energy surface for electron transfer. This plot was obtained from a Hartree-Fock wavefunction constrained to fit measured X-ray diffraction structure factors, using the Tonto program. See Jayatilaka & Grimwood [Acta Cryst. (2004), A60, 111-119].


topical reviews

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Recent progress in atomic resolution time-resolved synchrotron X-ray diffraction studies of molecular excited states is reviewed. Experimental and computational aspects of the field are discussed. Experimental results are compared with theoretical calculations on the excited state of the isolated species.

research papers

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The problem of coincidences between two planar lattices is analyzed using Clifford algebra.

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Patterns with octagonal and icosahedral symmetries obtained from periodic two-dimensional (2D) 8-grids and three-dimensional (3D) 12-grids by the dual method are shown to be superstructures of the Beenker pattern and the 3D Penrose pattern with the same edge length.

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An iterative method combining the charge-flipping algorithm and the dynamic Gerchberg–Saxton–Fienup algorithm is developed to reconstruct complex exit-wave functions of a non-periodic object.

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A systematic use of binary codes derived from the Hägg symbol are used to study close-packed polytypes. Seitz operators are introduced acting over the space of binary codes. Polytype counting problems are reduced to an eigenvector problem in the binary code space. Space groups of monoatomic close-packed polytypes can be seen as a result of the symmetry of the binary codes.

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Diffraction on a crystalline slab is treated as a multiple scattering problem based on the Ewald equations. The two-beam solution for both coplanar and non-coplanar cases valid near and far from Bragg peaks is found and a detailed comparison with results of Laue's theory is performed.

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A study of charge density in copper from a combination of quantitative convergent-beam electron diffraction and γ-ray diffractometry structure factors.

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The effect of limited alignment of hydrated proteins is considered in a laser-aligned molecular beam on diffraction patterns taken from the beam. A relationship between laser power, temperature and resolution is obtained, and simulations used to demonstrate iterative phasing of the continuous diffraction patterns.

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A simple calculation method of X-ray diffraction intensity in the n-beam case is constructed on the basis of kinematical theory for a small and ideally imperfect crystal. This method is interpreted as an integrated form of the intensity transfer equations proposed by Moon & Shull (1964).

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A method is presented to determine the projected potential of a crystal from a single exit-surface wavefunction obtained at atomic resolution under dynamical scattering conditions.

book reviews

books received

Acta Cryst. (2005). A61, 264
doi: 10.1107/S0108767304028569

international union of crystallography

Acta Cryst. (2005). A61, 300
doi: 10.1107/S0108767305005131
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