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Cover illustration: Crystal packing diagram of 1,4-benzoquinone with Hirshfeld surfaces. The translucent gray surfaces illustrate the nature of these novel surfaces and how they envelop each molecule and reflect the presence of neighbouring molecules. Colours mapped on the central surface represent the distance from the surface to the nearest nucleus in an adjacent molecule: red (shortest), through green, to blue (longest) (McKinnon, Spackman & Mitchell, Acta Cryst. B, in preparation). |
Acta Cryst. (2004). B60, 127-137 [ doi:10.1107/S0108768104000874 ]
Synopsis: The incommensurately modulated structure of ammonium fluoroberyllate is found to result from correlated rotations and displacements of the rigid complex ions according to a first harmonic modulation wave. The resulting changes in the network of the hydrogen bonds lead to the stabilization of the structure.
Online 18 March 2004
Acta Cryst. (2004). B60, 138-145 [ doi:10.1107/S0108768104001831 ]
Synopsis: X-ray diffraction and high-resolution electron microscopy show that crystallochemical equilibration of calcium-lead fluoro-vanadinite requires annealing at 1073 K for 2 weeks. The approach to equilibrium is controlled by the redistribution of lead ions into the apatite channels which expand to accommodate the larger cation.
Online 18 March 2004
Acta Cryst. (2004). B60, 146-154 [ doi:10.1107/S0108768104001843 ]
Synopsis: Structure refinement of calcium-lead fluoro-vanadinites by powder X-ray diffraction confirmed these apatites to be one-dimensional microporous solids containing tunnels that expand to accommodate larger cations through reduction in the metaprism twist angle. This trend can be modelled quantitatively by derivation from a regular triangular oxygen network.
Online 18 March 2004
Acta Cryst. (2004). B60, 155-162 [ doi:10.1107/S0108768104003325 ]
Synopsis: The structure of Na2S2O5 has been determined from a twin domain isolated by cleavage along a twin boundary. The metabisulfite ion does not adopt the Cs conformation observed in all other reported structures containing the anion.
Online 18 March 2004
Acta Cryst. (2004). B60, 163-173 [ doi:10.1107/S0108768104003647 ]
Synopsis: Quantitative symmetry and quantitative chirality measures were used to etablish correlations between pressure and temperature (PT) and the magnitude of these structural properties for the molecular building blocks of low quartz.
Online 18 March 2004
Acta Cryst. (2004). B60, 174-178 [ doi:10.1107/S0108768104002678 ]
Synopsis: The values of the lanthanide-oxygen bond-valence parameters calculated for coordination compounds, taking the coordination numbers into consideration, are presented.
Online 18 March 2004
Acta Cryst. (2004). B60, 179-183 [ doi:10.1107/S0108768104000540 ]
Synopsis: When determining crystal structures using X-ray diffraction methods, the H atoms are often left out in the dark because of their weak ability to interact with X-rays. In this article, a theoretical method of positioning H atoms is utilized.
Online 18 March 2004
Acta Cryst. (2004). B60, 184-190 [ doi:10.1107/S0108768104001739 ]
Synopsis: The charge density of L-tryptophan formic acid has been studied from a high-resolution synchrotron experiment with CCD area detection at 100 K. The results were compared with those of previous experimental studies and theoretical calculations. The topology of a strong hydrogen bond is discussed.
Online 18 March 2004
Acta Cryst. (2004). B60, 191-196 [ doi:10.1107/S0108768104003179 ]
Synopsis: The crystal structure appears as disordered and centrosymmetric, but the hydrogen-bond pattern shows that in reality it is the mixture of two tautomers that crystallize in one crystal with an exact 1:1 ratio.
Online 18 March 2004
Acta Cryst. (2004). B60, 197-203 [ doi:10.1107/S0108768104003696 ]
Synopsis: The disordered structure of 2-biphenylol shows no unusual behavior when cooled. At all temperatures above 90 K the drive for efficient packing is more important than the drive for the formation of O-H
O bonds.
Online 18 March 2004
Acta Cryst. (2004). B60, 204-210 [ doi:10.1107/S0108768104003775 ]
![[beta]](/logos/entities/beta_rmgif.gif)
-cyclodextrinSynopsis: In C53H85NO35·C3H7NO·15H2O, mono-6-deoxy-6-adamantylamide--cyclodextrin, units form a supramolecular linear polymer via self-assembly. Adjacent macrocycles in a column are linked by further hydrogen bonds. The water molecules, which reside in channels surrounding the columns of macrocycles, act as bridges between the cyclodextrin units.
Online 18 March 2004
Acta Cryst. (2004). B60, 211-218 [ doi:10.1107/S0108768104002770 ]
Synopsis: The crystal structures of three (N-phenylthioureidoalkyl- and -aryl)phosphonates have been determined by X-ray diffraction. The conformations of the title molecules, the geometry of the thioureide fragments and the molecular packing arrangements are analyzed and compared with literature data.
Online 18 March 2004
Acta Cryst. (2004). B60, 219-227 [ doi:10.1107/S0108768104003672 ]
Synopsis: The crystal structures of piperazine, piperidine and morpholine have been determined at 150 K. All three structures are characterized by the formation of NHN hydrogen-bonded chains. In piperazine these are linked to form sheets, but the chains are shifted so that the molecules interleave. In morpholine there are in addition weak CHO interactions. Packing in these three structures is compared to that observed in cyclohexane.
Online 18 March 2004
Acta Cryst. (2004). B60, 228-237 [ doi:10.1107/S010876810400312X ]
Synopsis: Global lattice-energy minimization with empirical potentials for the intermolecular and conformational energy predicts the ground state of biphenyl (phase III) to be a high-order superstructure, with periodic modulation of the twist angle of the molecule. The high-temperature phase I with a planar conformation is predicted to be a stationary point of the energy function, at a small height above the ground state.
Online 18 March 2004
Acta Cryst. (2004). B60, 238-248 [ doi:10.1107/S0108768104002344 ]
O, O-HN and C-H![[pi]](/logos/entities/pi_rmgif.gif)
(arene) hydrogen bondsSynopsis: Hydrogen-bonded adducts of triphenylsilanol, Ph3SiOH, with organic diamines form supramolecular structures containing isolated (zero-dimensional) aggregates or continuous structures in the form of a chain (one-dimensional), a sheet (two-dimensional) or a framework (three-dimensional).
Online 18 March 2004
Acta Cryst. (2004). B60, 249-251 [ doi:10.1107/S0108768104003714 ]
Synopsis: It is noted that La1/3NbO3 and La2/3TiO3, in which successive layers of A-sites are occupied by cations alternately to a greater and lesser degree, adopt the same orthorhombic structure. It is argued that a number of other perovskites, of the type Ln2/3TiO3, Ln1/3NbO3 and Ln1/3TaO3, where Ln is a lanthanoid, adopt this same structure.
Online 18 March 2004
Acta Cryst. (2004). B60, 252-253 [ doi:10.1107/S0108768104003878 ]
Synopsis: A recent survey of the Cambridge Structural Database shows that the percentage of incorrect assignments of the space group Cc has remained at about 10% since the last survey in 1997.
Online 18 March 2004
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