bluuebunny/crossref_metadata_2025_split huggingface dataset:
The crystal structure of Cu4Bi4Se9
Authors: Makovicky E. , Søtofte I. , Karup-Møller S. 
Published: December 2003

Abstract
The crystal structure of Cu4Bi4Se9, synthesized at 400 °C, was determined from single crystal X-ray diffraction data and refined to the R
1 value of 0.05. The compound is orthorhombic, with a = 32.692 Å, b = 4.120 Å, and c = 12.202 Å, space group Pnma. The structure contains three square pyramidal Bi sites, an octahedrally coordinated Bi site as well as two tetrahedrally and two irregularly coordinated Cu sites. The structure is an intergrowth of PbS-like slabs with irregularly configured slabs of Bi pyramids and Cu tetrahedra. It contains covalently bonded Se2 groups. Isotypy with Cu4Bi4S9 is connected with substantial changes in coordination details for two out of five distinct Cu sites. Modular relationships to the structures of the cuprobismutite series of Cu—Bi sulfosalts can be expressed as different ways of recombination of the same large structural fragment in the structures of Cu4Bi4Se9 and of the first cuprobismutite homologue, Cu4Bi5S10.
The crystal structure of Y2P4O13 from X-ray powder diffraction data
Authors: Ivashkevich L. S. , Lyakhov A. S. , Selevich A. F. , Ilieva D. , Lesnikovich A. I. 
Published: December 2003

Abstract
The crystal structure of Y2P4O13 has been determined from X-ray powder diffraction data. Y2P4O13 crystallizes in the orthorhombic space group C2221 (No. 20) with a = 17.2817(7) Å, b = 6.9823(4) Å, c = 8.5391(3) Å, V = 1030.38(8) Å3, and Z = 4. The structure has been solved by direct methods using EXPO program and refined by FULLPROF package. The final R
Bragg value was 9.1%. The tetraphosphate anion has the point group 2 symmetry. The yttrium atom is seven-coordinated forming strongly distorted octahedron with one bifurcated vertex. There are infinite chains of oxygen-bridged ittrium atoms running parallel to the b axis and linked together by the tetraphosphate anions with formation of three-dimensional network.
Dichloro-bis(2-chloro-2-phenyl-vinyl)Te(IV) and dibromo-bis(2-bromo-2-phenyl-vinyl)Te(IV): supramolecular self-assembly through different π-aryl interactions
Authors: Zukerman-Schpector Julio , Haiduc I. , Dabdoub M. J. , Biazzotto J. C. , Braga A. L. , Dornelles L. , Caracelli Ignez 
Published: December 2003

Abstract
C16H12Cl4Te, (1), Mr
= 473.66, P21/c, a = 8.3919(9), b = 14.474(1), c = 14.585(1) Å, β = 94.057(9)°, Z = 4, R
1 = 0.0378. C16H12Br4Te, (2), M
r = 651.50, Pnma, a = 19.159(2), b = 16.787(1), c = 5.781(1) Å, Z = 4, R
1 = 0.0437. In both compounds the primary geometry about the TeIV atom is a pseudo-trigonal-bipyramidal arrangement, with two halide atoms in apical positions, and the lone pair of electrons and C atoms in the equatorial plane. The TeIV atoms are involved in secondary interactions resulting in the self-assembly of a chain-like supramolecular array in (1) and into a three dimensional supramolecular array in (2). Compound (1) has a Z configuration with the chlorine atom and the tellurium moiety bonded at the same side in adjacent atoms. In (2) the bromine atom and the dibromotellurium moiety are bonded at adjacent carbons in a cis fashion.
Isomorphous phosphonoacetic acid salts with magnesium(II), manganese(II), cobalt(II), zinc(II) and copper(II)
Authors: Ślepokura K. , Piątkowska A. , Lis T. 
Published: December 2003

Abstract
All crystals of the title compounds, with general formula M2+(C2H4O5P–)2(H2O)2, (MAP), are isomorphous and crystallize in the space group P1̅ with Z = 2. The two crystallographically independent M2+ cations are situated on a center of symmetry and are octahedrally coordinated by two phosphonate monoanions and two water molecules. In the case of Cu2+ cation, Jahn-Teller effect causes strong extension of two Cu—O bonds. The mono anions coordinate the metal ions by one carboxylic and one phosphonate oxygen atom, which is facilitated by their specific overall conformation. In each monoanion, one of the phosphonate O atoms is nearly antiperiplanar ap to the carboxylic C atom, and the remaining phosphonate O atoms are nearly gauche (+sc and –sc) with respect to the mentioned C atom. The carboxylic O atoms are in positions close to +sc and –ac in relation to the phosphonate P atom. The complex molecules form well separated layers in all MAP compounds. The phosphonate and carboxylic groups act as donors in medium strong and weak intermolecular O—H...O hydrogen bonding and, as acceptors, in C—H...O hydrogen interactions in all structures. Additionally both crystallographically independent water molecules are donors of weak hydrogen bonding to phosphonate oxygen atoms from adjacent complex molecules.
Synthesis and structure of tris(triphenyltin)benzene-1,3,5-tricarboxylate and its tri-DMSO adduct
Authors: Dakternieks D. , Clarke D. J. , Tiekink Edward R. T. 
Published: December 2003

Abstract
The molecular structure of (Ph3SnO2C)3C6H3 reveals distorted tetrahedral C3O geometries for each tin atom. No intermolecular Sn...O associations occur between the molecules so that the trinuclear molecule may be considered monomeric. An increase in coordination number at tin is indicated by 119Sn NMR measurements conducted in d6-DMSO solution and this has been confirmed by a structure analysis of (DMSO·Ph3SnO2C)3C6H3·2 DMSO. In this structure, the tin atom geometries are distorted trigonal bipyramidal, existing within trans-C3O2 donor sets. Thus, while is it possible for the tin atoms to increase their coordination numbers in (Ph3SnO2C)3C6H3, molecular aggregation to form polymeric arrays is precluded, most likely due to steric constraints.
More power for direct methods: SIR2002
Authors: Burla M. C. , Carrozzini B. , Cascarano G. L. , Giacovazzo C. , Polidori G. 
Published: December 2003

Abstract
The program SIR2002, the heir of SIR2000-N, shows two important new features: a) a figure of merit which is able to recognize the trials potentially able to provide the correct solution; b) a procedure capable of exploiting electron density distributions misplaced with respect to the correct origin. The two features dramatically increase the power of direct methods for macromolecular crystallography.
Macromolecular phasing with SHELXE
Authors: Sheldrick G. M. 
Published: December 2003

Abstract
SHELXE was designed to provide a simple, fast and robust route from substructure sites found by the program SHELXD to an initial electron density map, if possible with an indication as to which heavy-atom enantiomorph is correct. This should be understood as a small contribution to high-throughput structural genomics. The new sphere of influence algorithm combined with a fuzzy solvent boundary enables some chemical knowledge to be incorporated into the density modification in a general and effective manner. In the special cases of high solvent content (greater than 0.6) or very high resolution data (better than 1.5 Å) high quality maps can be produced. This raises the possibility of a new paradigm for atomic resolution structure refinement: instead of alternating atom parameter refinement with weighted electron density maps calculated with the phases of the current model, which inevitably leads to some model bias, all model building should be based on the model free experimental density map!
Physical measurement of triplet invariants: present state of the experiment, data evaluation and future perspectives
Authors: Weckert E. , Müller R. , Zellner J. , Zegers I. , Loris R. 
Published: December 2003

Abstract
Invariant triplet phases can be determined experimentally by multi-beam interference experiments. In favourable conditions phases can also be determined from crystals of small macromolecules. The phase error is quite small, provided crystals of good quality are available. Single phases can be derived from triplet phases by means of maximum entropy based statistical methods. The number of experimental triplet phases necessary to solve a small protein crystal structure can be reduced by the application of an automatic refinement procedure. About 2.5 reflection phases per residue are necessary to solve the structure of a small protein if a high-resolution intensity data set is available.
Ab initio phasing starting from low resolution
Authors: Lunin V. Y. , Lunina N. , Podjarny A. , Bockmayr A. , Urzhumtsev A. 
Published: December 2003

Abstract
A single set of structure factor magnitudes complete at low resolution plus information of a general type are sufficient to get initial phases for macromolecular crystals which allow one to see the molecular packing and an approximate envelope. Followed by a more careful analysis based on the same information, these ab initio phases can be extended so that the corresponding maps show secondary structure elements.
Towards automated protein structure determination: BnP, the SnB-PHASES interface
Authors: Weeks C. M. , Blessing R. H. , Miller R. , Mungee R. , Potter S. A. , Rappleye J. , Smith G. D. , Xu H. , Furey W. 
Published: December 2003

Abstract
The direct-methods program SnB provides an efficient means for solving protein substructures containing many heavy-atom sites (current record: 160). In order to meet the high-throughput requirements of structural genomics projects, substructure determination needs to be tightly integrated with other aspects of the protein-phasing process. This has been accomplished through the design of a common Java interface, BnP, for SnB and components of PHASES, a popular and proven program suite that provides all the tools necessary to proceed from substructure refinement to the computation of an unambiguous protein electron-density map. Therefore, BnP will facilitate a high degree of automation and enable rapid structure determination by both experienced and novice crystallographers.
Direct way to anomalous scatterers
Authors: Dauter Z. , Nagem R. A. P. 
Published: December 2003

Abstract
The first step in solving macromolecular crystal structures by multi- or single-wavelength anomalous diffraction methods is the location of the anomalous scatterers. This can be done by direct methods, using either Bijvoet differences within the single data set, or anomalous scattering amplitudes estimated from measurements at several wavelengths. The calculations suggest that Bijvoet differences are equally successful for this purpose as anomalous amplitudes, F
A, which theoretically should be more suitable. The calculation of F
A values is susceptible to the accumulation of errors contained in the individual intensity measurements at several wavelengths and in the inaccurate estimation of the anomalous atomic scattering corrections, f′ and f″. Direct methods often give better results at resolution lower than the full extent of the diffraction data limit. This may be attributed to the enhanced accuracy of measurements of the strong, low resolution reflections and to more effective phase refinement and propagation through Σ2 relations.
The approach of the joint probability distribution functions: the SIR-MIR, SAD-MAD and SIRAS-MIRAS, cases
Authors: Giacovazzo C. , Ladisa M. , Siliqi D. 
Published: December 2003

Abstract
The method of the joint probability distribution functions has been recently applied to SIR-MIR, SAD-MAD and SIRAS-MIRAS cases. The capacity of the method to treat various forms of errors (i.e., errors in measurements, possible lack of isomorphism, errors in a substructure model when a model is a priori available, etc.) is the most innovative aspect of the approach. The description of the technique and the analysis of the conclusive formulas are dispersed in a number of papers; this contribution offers a unified point of view for all the cases and a perspective for future applications.
Direct-method phasing of anomalous diffraction from proteins
Authors: Gu Y. X. , Jiang F. , Sha B. D. , Fan H. F. 
Published: December 2003

AbstractIn dealing with anomalous diffraction data from proteins, the probability distribution of three-phase structure invariants provides additional information, which can be used to resolve the phase ambiguity intrinsic in single-wavelength anomalous diffraction (SAD) enabling solution of the protein structure. Based on this, direct methods have also been used in phasing multi-wavelength anomalous diffraction (MAD) data leading to better result than that from the conventional MAD phasing.
Molecular replacement and high-throughput structure determination
Authors: Navaza J. , Alzari P. M. 
Published: December 2003

Abstract
We describe the philosophy of the MR method as implemented in the AMoRe package. Fast rotation and translation functions are first used to obtain a meaningful sampling of solution space, whose elements are subsequently assessed by using more robust criteria. The introduction of fast and accurate algorithms for screening a large number of possible solutions opened the way to automation, thus bringing MR methods to the realm of high-throughput structure determination. Selected examples are discussed to illustrate specific aspects of the method.
Chemical short range order obtained from the atomic pair distribution function
Authors: Proffen Th. , Petkov V. , Billinge S. J. L. , Vogt T. 
Published: December 2003

Abstract
Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Local structural information can be obtained by analyzing the atomic pair distribution function (PDF) obtained from powder diffraction data. In this paper, we present the successful extraction of chemical short range order parameters from the x-ray PDF of a quenched Cu3Au sample.
Refinement of the crystal structures of Cu3PS4and Cu3SbS4and a comment on normal tetrahedral structures
Authors: Pfitzner Arno , Reiser S. 
Published: December 2003

AbstractThe crystal structures of yellow Cu3PS4and of black Cu3SbS4were refined from single crystal X-ray diffraction data. Cu3PS4crystallizes orthorhombic in an ordered wurtzite superstructure type with the space groupPmn21(no. 31),a= 7.282(1) Å,b= 6.339(1) Å,c= 6.075(1) Å,V= 280.38(8) Å3, andZ= 2. The refinement converged toR= 0.0276, andwR2 = 0.0710 for 737 unique reflections and 44 parameters. Cu3SbS4crystallizes tetragonal in an ordered sphalerite superstructure type with the space groupI4̅2m(no. 121),a= 5.391(1) Å,c= 10.764(1) Å,V= 312.83(9) Å3, andZ= 2. The refinement converged toR= 0.0213, andwR2 = 0.0532 for 492 unique reflections and 14 parameters. The crystal structures of the title compounds and related normal tetrahedral structures are discussed with respect to the preference of either hexagonal or cubic packing of the anions.
Crystal structure of K1-

x
Cs
x
BSi2O6 (x = 0.12, 0.50) boroleucite solid solutions and thermal behaviour of KBSi2O6 and K0.5Cs0.5BSi2O6
Authors: Bubnova R. S. , Levin A. A. , Stepanov N. K. , Belger A. , Meyer D. C. , Polyakova I. G. , Filatov S. K. , Paufler P. 
Published: December 2003

Abstract
The crystal structures of two K1-

x
Cs
x
BSi2O6 solid solutions have been refined at room temperature by the Rietveld method: x = 0.12, a = 12.6858(4) Å, Rwp
= 7.66%, R
F = 5.56% and x = 0.50, a = 12.8480(2) Å, Rwp
= 7.64%, R
F = 3.10%. They are isostructural to cubic KBSi2O6 with the space group I4̅3d. The structure is built up from (Si,B)O4 tetrahedra linked in four-, six- and eightfold rings which are forming a three-dimensional borosilicate framework. The framework contains large cavities that are placed in continuous channels along the [111] directions. The Cs and K atoms occupy the positions in the channels statistically. Thermal behaviour of KBSi2O6 and K0.5Cs0.5BSi2O6 has been studied by high-temperature powder X-ray diffraction within the temperature range of 293-1073 K. A new tetragonal polymorph of KBSi2O6 has been found in situ under heating. The new polymorphic I4̅3d (cubic) – Ia3̅d (cubic) transition and the new Ia3̅d cubic polymorphic phase has been proposed for K1-

x
Cs

x

BSi2O6 from our experimental and literature data on crystal structures and thermal expansion of leucites. The structural relaxation under cationic (K, Cs) substitutions and under heating has been investigated.
The crystal structure of Na3HP2O7 ⋅ H2O from X-ray powder diffraction data
Authors: Ivashkevich L. S. , Selevich K. A. , Lyakhov A. S. , Selevich A. F. , Petrusevich Yu. I. 
Published: December 2003

Abstract
The crystal structure of Na3HP2O7 ⋅ H2O has been determined from X-ray powder diffraction data. The structure is monoclinic, space group P21/n (No. 14), with unit cell dimensions a = 10.4242(1) Å, b = 6.8707(1) Å, c = 10.0837(1) Å, β = 99.2258(7)°, V = 712.87(2) Å3, Z = 4, D
m = 2.43 g/cm3 and D
x = 2.41 g/cm3. The structure has been solved by direct methods using EXPO program and refined by FULLPROF package. The final R
Bragg value was 7.6%. Positions of hydrogen atoms were not defined. There are three sodium cations in the asymmetric unit. Two of them are five-coordinated and one cation has sixfold oxygen coordination. Each HP2O7
3– anion is hydrogen bonded to its two adjacent neighbours forming infinite chains parallel to the b axis. Water molecules are located in infinite channels extended along the b direction. The oxygen atom of the water molecule is connected with two sodium cations and hydrogen bonded with one oxygen atom of diphosphate group.
The glass transition in twinned ((phenyl)4As)2C60Cl crystals
Authors: Pilz K. , Jobst A. , Lam E. , Lüdecke J. , van Smaalen S. , Bao J. , Bietsch W. , Schwoerer M. 
Published: December 2003

Abstract
We have studied the crystal structure of ((phenyl)4As)2C60Cl at room temperature and below the phase transition at Tc
= 125 K by single-crystal x-ray diffraction. At room temperature tetragonal lattice parameters were found as a = b = 12.588(1)Å and c = 20.345(1)Å. At T = 120 K the lattice parameters were determined as a = b = 12.5060(1)Å and c = 20.4420(1)Å. The room temperature and low-temperature structures were found to be isostructural, with space group I4/m. Structure refinements were performed with restrictions on the C60 molecules according to the noncrystallographic isohedral point symmetry Ih
. Derivations from this symmetry could not be found, suggesting that any possible Jahn-Teller distortion of the C60 radical anions will be smaller than 0.01Å. The phase transition observed in ESR at Tc
= 125 K is proposed to be a glass transition. At room temperature there is dynamic disorder between two orientations of the C60 molecules as they are related by the 4-fold rotation. Below Tc
the disorder becomes static. Two types of twinning have been observed in different crystals. The first type is represented by a rotation over 180 about [1,1,1] axis. It results in different orientations of the 4-fold unique axes with angles of 82.4 degrees between them. Secondly, merohedral twinning was observed corresponding to the two orientations of the structure with 4/m symmetry on the tetragonal lattice. Both twinnings result in extra orientations of the C60 molecules, and they should be taken into account, when analysing the anisotropy of the physical properties of crystals of this compound.
Least-squares refinements of crystal structures: leverage analysis and the effects of truncating data
Authors: Merli M. 
Published: December 2003

Abstract
The treatment of weak intensities in the least-squares refinement of crystal structures is a quite controver-sial subject. According to the predominant opinion, all of the collected intensities should be used in the structure refinement process. Sometimes, however, the omission of the weakest data seems to be not influent, and sometimes it can even improve the refinement results. In the present work the effects of selectively excluding reflection with low I/u(I) ratio from both |Fo| and Fo
2 least-squares refinements are examined for Trimethopin-Sulfametoxypyridazine 1:1 and N′-(4-methoxyphenyl)-N-phenyl-N-oxyformamidinium. An interpretation of some observed features of the results of the least-squares refinements by means of the leverage analysis is proposed.
Monte Carlo Study of the quasicrystal-to-crystal transformation using an approach based on the Gummelt covering
Authors: Honal M. , Welberry T. R. 
Published: December 2003

Abstract
A tiling representation and associated possible tiling flips are developed for the "unit-cluster" description of decagonal quasicrystals with reference to the example of decagonal Al70Co15Ni15. A perfect P1 tiling is a suitable model of the ideal quasiperiodic structure and a 180° flip of a pentagon tile can be used as an analogue of the hexagon flips in Penrose rhomb tilings. Monte Carlo simulations and calculated diffraction patterns are used to study the effect of those tiling flips on the cluster scale for some example cases. Some of these have a special importance for the quasicrystal-to-crystal transformation. Starting with the perfect P1 tiling the system is allowed to evolve using phason fluctuations whose probabilities depend on the resulting local tile configurations. The degree of order/disorder introduced and its effects on the diffraction pattern are investigated.
Crystal structure analysis, pseudosymmetry and spectroscopic data of K4[Fe(CN)5NO2]⋅KNO2⋅H2O
Authors: Woike Th. , Himmelreich U. , Henke Henning , Bärnighausen H. 
Published: December 2003

Abstract
K4[Fe(CN)5NO2]⋅KNO2⋅H2O crystallizes in the non-centrosymmetric orthorhombic space group Bb21
m (no. 36) with a = 2698.2(3), b = 1415.7(1), c = 849.6(1) pm and Z = 8 at 291 K. Due to a high degree of pseudosymmetry the deviations from centrosymmetry are small. The gross arrangement of the iron and potassium atoms is that of the AlB2-type, discernible from the distorted hexagons of the boron-analogous part with the composition FeK3 while further potassium atoms are replacing Al in agreement with the formulation K2[FeK3]. The disorder of the free nitrite ions affiliated to KNO2 is characterized by means of additional data sets collected at temperatures of 173 K and 363 K. The results of the structure analysis are confirmed by infra-red spectroscopy. Especially the deformation modes δ(O-N-O) of the free nitrite and those of the nitro ligand show the expected frequency splitting. Mössbauer data serve as a check on chemical composition and give an independent estimate for the mean square displacement of the iron (57Fe) atoms comparable to the results from X-ray diffraction. The loss of crystal water above 400 K is registered using ther-mogravimetry and differential scanning calorimetry.
Stacking disorder in 2H-NbS2 and its intercalation compounds K
x
(H2O)
y
NbS2 I. Description and model calculations of stacking faults in the host lattice NbS2
Authors: Katzke H. 
Published: December 2003

Abstract
A quantitative modelling of the disorder phenomena in layered NbS2 is presented. The polytypes 2H and 3R are considered and the variations of the intensity profiles for their transformations into each other are calculated in terms of a one-dimensional disorder model.
[Cu(imidazole)2(CO3)]⋅H2O: an intermediate in the formation of the copper bis-imidazolate polymer (blue phase)
Authors: Masciocchi N. , Bruni S. , Cariati E. , Galli S. , Sironi A. 
Published: December 2003

Abstract
The crystal structure of [Cu(Him)2(CO3)]·H2O, determined from conventional X-ray powder diffraction methods, allowed to clarify, on the basis of a structural interpretation of the chemical transformation, the role of the title compound in the formation of the blue phase of Cu(im)2 [Cu(Him)2(CO3)]·H2O is triclinic, P1̅; a = 8.8565(7), b = 8.9579(5), c = 8.3705(6) Å, α = 105.728(4)°, β = 105.318(3)°, γ = 114.369(4)°; final Rwp
, Rp
and RF
agreement factors, for 4700 data collected in the 11–105° range, are 0.053, 0.036 and 0.078, respectively.