Acta Crystallographica Section BActa Crystallographica Section B: Structural Science publishes papers in which structure is the primary focus of the work reported. The central themes of Structural Science are the acquisition of structural knowledge from novel experimental observations or from existing data, the correlation of structural knowledge with physico-chemical and other properties, and the application of this knowledge to solve problems in the structural domain. Structural Science has broad chemical coverage,...Experimental electron density study of ethylene oxide at 100K- May 15, 2008 The experimental electron density of ethylene oxide was derived from a multipole refinement of 100K X-ray data and complemented by density-functional calculations at experimental and optimized geometry. Atomic and bond-topological properties were derived using the atoms-in-molecules (AIM) formalism. The high strain in the three-membered ring molecule is mainly expressed by the high ellipticities of the three bonds in this ring, while the bond paths are only slightly bent for the CC bond, but...http://scripts.iucr.org/cgi-bin/paper?bs5059 Coherence length of the KY(WO4)2 single crystal- May 15, 2008 Potassium yttrium tungstate is a monoclinic crystal with space group C2c. The specific X-ray investigations presented in this article determine the coherence scattering length for this crystal. The scattering profiles were obtained using a Philips MRD X-ray diffractometer. The WilliamsonHall method was used to determine the coherence scattering length and internal stresses.http://scripts.iucr.org/cgi-bin/paper?lm5015 Comparative experimental electron density and electron localization function study of thymidine based on 20K X-ray diffraction data- May 15, 2008 From a high-resolution X-ray data set (sin = 1.11) measured at 20K the electron-density distribution of the nucleoside thymidine was derived by a classical multipole refinement and by application of the invariom formalism. Owing to the presence of the heteroaromatic thymine ring system two invariom models were compared which considered the nearest and next-nearest neighbors for the invariom assignments. Differences between the two invariom models were small for the bond topological and atomic...http://scripts.iucr.org/cgi-bin/paper?sn5064 Structural analysis of perovskite LaCr1xNixO3 by Rietveld refinement of X-ray powder diffraction data- May 15, 2008 The crystal structure of perovskite LaCr1xNixO3 (0 x 1.0) has been systematically investigated by analyzing X-ray powder-diffraction data taken at room temperature. Rietveld refinement has confirmed the structural evolution from the orthorhombic phase (Pbnm, Z = 4) to the two-phase (the orthorhombic and the rhombohedral phases) region around x = 0.7, then to the rhombohedral (Rbar 3c, Z = 2) phase for 0.8 x 1.0. The lattice parameters are also obtained in the refinement process. The results.http://scripts.iucr.org/cgi-bin/paper?bp5009 On the crystal chemistry of olivine-type germanate compounds, Ca1+xM1xGeO4 (M2+ = Ca, Mg, Co, Mn)- May 15, 2008 Germanate compounds, CaMGeO4 with M2+ = Ca, Mg, Co and Mn, were synthesized as single crystals by slow cooling from the melt or by flux growth techniques. All the compositions investigated exhibit Pnma symmetry at 298K and adopt the olivine structure. The M2 site is exclusively occupied by Ca2+, while on M1 both Ca2+ and M2+ cations are found. The amount of Ca2+ on M1 increases with the size of the M1 cation, with the smallest amount in the Mg compound (0.1atoms per formula unit) and the...http://scripts.iucr.org/cgi-bin/paper?ws5059 Vacancy-ordering effects in AlB2-type ErGe2 x(0.4 < x 0.5)- May 15, 2008 In the ErGe system, the compostion range ErGe2 to Er2Ge3 has been investigated. Eight samples were produced by arc melting of the elements, and analyzed using X-ray powder diffraction. Nine crystal structures were found to be present in the samples. The structures are described as a homologous series and presented within the superspace formalism using the superspace group X2m(0)0s, X representing the centring vector (, , 0, ). In this description the modulation vector q = (a + c) is shown to be.http://scripts.iucr.org/cgi-bin/paper?ck5030 Hydrogen-bonding properties of galanthamine: an investigation through crystallographic database observations and computational chemistry- May 15, 2008 The hydrogen-bonding properties of galanthamine have been investigated experimentally from a thorough analysis of crystallographic data retrieved from the Protein Data Bank and Cambridge Structural Database databases and theoretically through ab initio MP26-311++G(2d,p) and density functional theory MPWB1K6-31++G(d,p) calculations. The main hydrogen-bond acceptor (HBA) interaction sites of the molecule are the O atoms and their spatial proximity allows multi-centered hydrogen-bond (HB) motifs...http://scripts.iucr.org/cgi-bin/paper?ry5017 Hydrogen bond strength and bond geometry in cyclic dimers of crystalline carboxylic acids- May 15, 2008 In a study of 101 crystal structures of carboxylic acids we have observed a clear trend in the difference between the formally single and formally double CO bond distances, as observed by X-ray diffraction, with a clear-cut distinction between aromatic acids, where the two distances are similar, and non-aromatic acids, where the two distances distinctly differ by 0.060.12. A tentative energy classification within the limits of the many assumptions and a correlation with the O...O separation...http://scripts.iucr.org/cgi-bin/paper?bs5060 |