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May 2005 issue
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].
research papers
High-resolution measurement of absolute lattice parameter, strain and composition in single-crystal layers by the zone technique is discussed. The method enables rapid and simultaneous determination of several interplanar spacings for each layer with a potential resolution of a few parts in ten million.
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Multitemperature X-ray data for D,L-serine were evaluated using invarioms, which are theoretically derived multipole-model pseudoatoms that remain approximately invariant in an intermolecular transfer. Invariom modeling improves molecular geometry, especially for H atoms and the description of thermal motion.
A scheme for carrying out phase reconstruction from a series of astigmatic diffraction patterns in an electron microscope is presented.
For the transition from the wurtzite to the NaCl type, a new transition path is presented that is based on the deformation of a lonsdaleite configuration into a cubic primitive lattice cP using symmetry Pnma.
All types of homogeneous sphere packing and interpenetrating sphere packings and layers were derived that correspond to point configurations of the 15 trivariant hexagonal lattice complexes. Examples of related crystal structures are given.
The case of imperfect partial structures has been revisited via the method of joint probability distribution functions.
A new 17-atom cluster is proposed and thoroughly discussed and compared with the 33-atom Gummelt cluster. Structure factors for these clusters are calculated with a statistical approach.
There are 0, 23, 136 and 710 isohedral simple tilings by tiles of <14, 14, 15 and 16 faces, respectively.
The method of prior-derived F constraints is proposed as a new method to reduce artifacts and noise in electron-density maps reconstructed by the maximum-entropy method.
Modern X-ray optics can produce a focused synchrotron beam with curvature on a scale comparable to that of an isolated biomolecule or to the lattice spacing of a biomolecular crystal. It is demonstrated that diffraction of phase-curved beams from such systems allows unique and robust phase recovery.
short communications
Tables of crystallographic properties of the magnetic subperiodic groups are presented.
