J. Appl. Cryst. (2008), 41, 491-522. Â Â [ doi:10.1107/S0021889808007279 ]
Most modern small-molecule refinement programs are based on similar algorithms. Details of these methods are scattered through the literature, sometimes in books that are no longer in print and usually in mathematical detail that makes them unattractive to nonprogrammers. This paper aims to discuss these … Read the rest
J. Appl. Cryst. (2008), 41, 531-536. Â Â [ doi:10.1107/S0021889808005463 ]
Librational motion within a crystal structure distorts the measured bond distances and angles from their physical values. TLS analysis of a rigid molecule or a rigid part of a molecule allows the calculation of bond-length and angle corrections. Until now, no estimate of the error … Read the rest
The Annual Meeting of the British Crystallography Association was held in York. Contributions from Chem. Cryst. included:
Anna Collins, Richard I. Cooper, Andrew R. Cowley, David J. Watkin
2-(1-Hydroxy-2-methyl-propyl)-2,5-dihydro-furan-2-carboxylic acid diisopropylamide: A study of a phase transition to a pseudosymmetrical Z′=2 structure (Poster)
James Haestier, Mustapha. Sadki, Amber L. Thompson and David J. Watkin
Cell … Read the rest
I worked with Keith for 40 years. When I came to Oxford in 1967 as a fresh post doc, Keith was already the Lecturer in Chemical Crystallography, running a successful research group alongside those of Tiny Powell and Dorothy Hodgkin. Although he was not my supervisor, I quickly learned that it was he who held … Read the rest
Acta. Cryst. (2007), 63, 303-308. [ doi:10.1107/S0108768106055212 ]
A new polymorph of 2,4-dihydroxybenzoic acid is reported. The structure was characterized by multiple-temperature X-ray diffraction and solid-state DFT computations. The material shows a geometric pattern of hydrogen bonding consistent with cooperativity between the intermolecular carboxylic acid dimer and intramolecular hydrogen bonds. The presence of proton … Read the rest
J. Appl. Cryst. (2006), 39, 842-849. Â Â [ doi:10.1107/S0021889806038489 ]
A sizeable proportion of structures with Z‘ = 2 are thought to exhibit pseudosymmetry, but establishing the extent of the deviation from true symmetry is problematic. By considering both the conformational similarity between the independent molecules and the way in which they are related … Read the rest
In October, Lynn Nickerson (Science Club Coordinator at Didcot Girls School) arranged for a small group to visit Chemical Crystallography in Oxford University’s new Chemistry Research Laboratory (Figure 1). The group was invited to bring some samples of common crystalline materials with them. The samples brought included cane sugar and citric acid (Figure 2). The … Read the rest
J. Chem. Inf. Comput. Sci. (2004), 44, 2133-2144. [ doi:10.1021/ci049780b ]
The crystallographically determined bond length, valence angle, and torsion angle information in the Cambridge Structural Database (CSD) has been made accessible by development of a new program (Mogul) for automated retrieval of molecular geometry data from the CSD. The program uses a system … Read the rest
Lecture on the uses of crystallography during Part-II research year.… Read the rest
Acta. Cryst. (2004), A60, 322-325. [ doi:10.1107/S010876730401219X ]
β-U4O9 is a superlattice structure based on the fluorite arrangement of UO2. The U atoms occupy positions close to those in UO2 and the additional O atoms are accommodated in cuboctahedral clusters of -43m symmetry, which are centred on the special … Read the rest