bluuebunny/crossref_metadata_2025_split huggingface dataset:
9,10 Phenanthrenequinone, not your average structure
Authors: Rae A. David , Willis A. C. 
Published: December 2003

Abstract
9,10-phenanthrenequinone, C14H8O2, is both polymorphic and polytypic. The β form can have different symmetries arising from different stackings of ordered layers perpendicular to c
p*. These structure options are best understood using occupancy wave modulations of a 1 : 1 disordered parent structure in space group P21/c. The disorder is resolved by having ordered layers of C1̅ symmetry in a cell with a = 2a
p, b = 2b
p. Ordering the stacking sequence allows two orientations of a Z = 8, Cc, c = c
p structure and two orientations of a Z = 16, F1̅, c = 2c
p structure. It was found that for some crystals it is necessary to model the reflection data assuming uncorrelated mosaic blocks of different space group symmetry as well as orientation. Reliable geometry for both the Cc and F1̅ components were then obtained. Likewise, the α form can be described as arising from a 1 : 1 disordered parent structure in space group Pnmn where the disorder is resolved by having ordered layers of P2/c symmetry perpendicular to a
p* in a cell with b = b
p, c = 2c
p. Ordering the stacking sequence allows two orientations of a Z = 4, P21
cn structure with a = a
p and two orientations of a Z = 8, B2/c structure with a = 2a
p (a non standard setting of P2/c).
A comparative study of pressure-induced lattice strain of α- and γ-polymorphs of glycine
Authors: Boldyreva E. V. , Ahsbahs H. , Weber H.-P. 
Published: December 2003

Abstract
The effect of hydrostatic pressure up to 4 GPa on the two polymorphs of glycine α — s.g. P21/n, and γ — s.g. P31 (P32)) was studied by X-ray powder diffraction using a synchrotron radiation source (λ = 0.7 Å, a MAR345 image plate detector). No polymorphic transformations were detected. Relative volume changes and the aniso tropy of structural distortion of the two polymorphs were compared. The directions of maximum and minimum lattice strain were related to the directions of weak and strong hydrogen bonds in the structures.
Correlations, convolutions and the validity of electron crystallography
Authors: Dorset Douglas L. 
Published: December 2003

AbstractAlthough often an object of controversy, electron crystallography has emerged as a useful technique for characterization of the microcrystalline state, capable of elucidating crystal structures of unknown substances. Despite the complicated multiple scattering perturbations to diffracted intensities, experimental conditions can be adjusted to favor data collection where the experimental Patterson function still resembles the autocorrelation function of the actual crystal structure. Satisfying this condition is often sufficient to permit structure solution from such data by direct methods. While the application to organic structures may seem obvious, there are surprising successes with data sets from inorganic materials. The account given in this paper, in part, portrays work leading to the A. L. Patterson Award to the author from the American Crystallographic Association.
The quantitative analysis of electrostatic potential and study of chemical bonding by electron diffraction structure analysis
Authors: Avilov A. S. 
Published: December 2003

Abstract
The development of the electron diffractometry methods jointly the analytical methods of electrostatic potential (ESP) reconstruction and its topological analysis allowd one to proceed to the quality new level of electron diffraction structure analysis (EDSA): investigation inner crystalline electrostatic field, which knowledge permitts to study the relation of the atomic structure with physical properties of crystals. The review of the last achivements in this direction, obtained in the Institute of Crystallography of Russian Academy of Sciences, in which EDSA method was discovered, is done. The possibility of the EDSA method to solve precise problems of quantitative analysis of the electrostatic potential is shown on the examples of investigations of the ESP distributions and chemical bonding in crystals with NaCl-type structure and covalent crystal Ge. It is also shown that quantitative data on the potential distribution considerably enlarge conceptions on the nature of interatomic and inetrmolecular interactions in crystals.
Electron crystallography on polymorphic organics
Authors: Kolb U. , Matveeva G. N. 
Published: December 2003

AbstractOrganic materials, such as non-linear optical active compounds (1-(2-furyl)-3-(4-aminophenyl)-2-propene-1-one (FBAPPO) and 1-(2-furyl)-3-(4-benzamidophenyl)-2-propene-1-one (FAPPO)), polymeric materials like the metal coordinated polyelectrolyte (Fe(II) [ditopic bis-terpyridin] (MEPE)) or polymorphic materials (e.g. Cu-phthalocyanine), which do not crystallize big enough for single crystal x-ray structure analysis have been investigated by electron diffraction (ED) at 100 and 300 kV acceleration voltage. Sample preparation (direct crystallization, ultra sonication, ultra microtomy), diffraction strategies (selected area diffraction, nano diffraction, use of double-tilt rotation holder), data collection and data processing as well as structure solution strategies have been chosen dependent on the different requirements of the compounds under investigation. Structure analysis was carried out by simulation usingab initioquantum-mechanical methods like density functional theory (DFT), semi-empirical approach (MNDO/AM1/PM3) and force field packing energy calculations (DREIDING). The structure models resulting from simulation were refined kinematically as rigid bodies. Subsequently, refinements by multi-slice least squares (MSLS) procedures taking dynamical scattering into account were performed. The described combination of different methods which was used successfully on crystallizable materials is also adaptable to insoluble organic materials (e.g. pigments) and polymorphic systems.
Electron diffraction structure analysis: structural research with low-quality diffraction data
Authors: Weirich Th. E. 
Published: December 2003

Abstract
Electron Diffraction Structure Analysis (EDSA) with data from standard selected-area electron diffraction (SAED) is still the method of choice for structure determination of nano-sized single crystals. The recently determined heavy atom structure α-Ti2Se (Albe & Weirich, 2003) is used as an example to illustrate the developed procedure for structure determination from two-dimensionally SAED data via direct methods and kinematical least-squares refinement. Despite the investigated crystallite had a relatively large effective thickness of about 230 Å as determined from dynamical calculations, the obtained structural model from SAED data was found in good agreement with the result from an earlier single crystal X-ray study (Weirich, Pöttgen & Simon, 1996). Arguments, which support the validity of the used quasi-kinematical approach, are given in the text. The influences of dynamical and secondary scattering on the quality of the data and the structure solution are discussed. Moreover, the usefulness of first-principles calculations for verifying the results from EDSA is demonstrated by two examples, whereas one of the structures was unattainable by conventional X-ray diffraction.
Effect of diffraction crystallography on HREM
Authors: Li Fang-hua 
Published: December 2003

Abstract
A simple image contrast theory in high-resolution electron microscopy (HREM) is introduced to demonstrate that below a certain critical crystal thickness the intensity of the Scherzer focus image is linear to the projected potential of an artificial crystal that is isomorphic to the examined one. It has become the theoretical base of electron crystallographic image processing techniques relying on the weak-phase-object approximation and kinematical diffraction. Two techniques of image processing are introduced. One of them aims at determining crystal structures by combining electron diffraction data and applying diffraction analysis methods. To reduce various kinds of electron diffraction intensity distortion the diffraction data are corrected by means of an empirical method set up by referring to the heavy atom method and Wilson statistic. The other one aims at revealing crystal defects at atomic resolution from the image taken with a medium-voltage field-emission high-resolution electron microscope. The dynamical effect is corrected by forcing the integral amplitudes of reflections in the diffractogram of image equal to the amplitudes of corresponding structure factors for the perfect crystal. The principle of the two techniques is briefly introduced, and examples of applications to crystal structure and defect determination are given.
Electron crystallography of aluminum alloy phases
Authors: Gjønnes J. , Hansen V. , Andersen S. J. , Marioara C. D. , Li X. Z. 
Published: December 2003

Abstract
A series of structure analyses during 1994-2001 by electron crystallographic techniques applied to phases in aluminum alloys are reviewed. Methods for structure solution employ electron diffraction intensity data collected by the precession technique, by selected area micro-diffraction and by the convergent-beam technique. High-resolution electron microscope images (HRTEM) are treated by different kind of processing, including exit wave reconstruction. Crystallographic calculations are performed either by direct method or Patterson and Fourier procedures, assuming kinematical scattering, or by refinement from models derived from HRTEM images. Dynamical scattering calculations can be introduced in the refinement stage or as a correction procedure applied to part of the intensity data. The phases studied include primary Al-Fe-(Si) particles, Al-Mn-Si dispersoids, Al-Co quasicrystals and two types of precipitate phases in age-hardening Al-Mg-Si and Al-Zn-Mg alloys.
Visual computing in electron crystallography
Authors: Wan Z. , Liu Y. , Fu Z. , Li Y. , Cheng T. , Li F. , Fan H. 
Published: December 2003

AbstractVECis a program package forVisual computing inElectronCrystallography. The program is written mainly in C++ and Fortran and is for running underMS Windows95, 98, NT and 2000. Apart from its user-friendly interface, sophisticated text-sensitive online helps and tutorials,VECincludes same unique crystallographic methods. They are direct-method image-processing techniques,ab-initiosolution of incommensurate crystal structures and algorithms for searching one-dimensionally modulated atoms in 4-dimensional Fourier maps. Examples are given in details.
Anomalous thermal expansion behaviour of Na8[AlSiO4]6(NO3)2-sodalite:P4̅3ntoPm3̅nphase transition by untilting and contraction of TO4units
Authors: Rüscher C. H. , Gesing Th.M. , Buhl J.-Ch. 
Published: December 2003

AbstractX-ray single crystal, X-ray powder and specific heat investigations were carried out on alumosilicate NaNO3-sodalite between 290 K and 1100 K. Single crystal structure determinations at 295 K, 505 K and 720 K reveal the sodalite structure in its partially collapsed form in space groupP4̅3nwhereas at 935 K the z coordinate of the framework oxygen is shifted toz= 0.5 according to an untilted sodalite framework inPm3̅n. The sodium ions are located on 8e(x, x, x) position inP4̅3nand become statistically distributed on 16i(x, x, x) inPm3̅n. The displacements of the nitrate atoms are extraordinarily enlarged at 935 K compared to the values at the lower temperatures. Analysis of the X-ray powder data show a discontinuity in the thermal expansion behaviour atTc= 930 K with the temperature dependence of the lattice parameter described byacalc=a1—A(Tc—T)0.5,a1=BT+a0(A= 0:57 pm K–0.5,B= 5:84 · 103pm K–0.5,a0= 909.9 pm,Tin K) which is related to a square root decrease of the volume strain. The anomalous thermal expansion compromises a gradual contraction of TO4units and the disappearence of structural tilt with increasing temperature. The refined data reveal a change of z coordinate of O1 proportional to (Tc-T)1/4inP4̅3nwhich is considered as an effective order parameter in a Landau tricritical description of the phase transition triggered by the displacement of the cage filling ions.
Crystal structure of new hexahydrate dicobalt pyrophosphate Co2P2O7·6H2O: comparison with Co2P2O72H2O, α-, β- and γ-Co2P2O7
Authors: Capitelli F. , Harcharras M. , Assaaoudi H. , Ennaciri A. , Moliterni A. G. G. , Bertolasi V. 
Published: December 2003

Abstract
A new dicobalt pyrophosphate, Co2P2O7·6H2O, has been synthesized and characterized by single crystal X-ray diffraction. The compound belongs to the mono clinic space group P21/n, and its unit cell dimensions are: a = 7.2077(2), b = 18.3373(5), c = 7.6762(2) Å, β = 92.4356(15)°, V = 1013.64(5) Å3, Z = 4. The structural parameters were refined to an R index of 0.0570 for 1937 reflections with I>2σ(I
o). The framework of this pyro phosphate is made by the packing of layers of discrete CoO6 octahedra connected by double tetrahedra P2O7 groups. The (P2O7)4– anion group shows bent eclipsed conformation. A comparative study among anhydrous (α-, β- and γ-Co2P2O7) and hydrated forms (Co2P2O7·2H2O) of dicobalt pyrophosphates known in literature is presented.
Crystal structures and Raman spectra of Cu(OH)F and Cu3(OH)2F4
Authors: Giester G. , Libowitzky E. 
Published: December 2003

AbstractCrystals of Cu(OH)F and Cu3(OH)2F4have been synthesized at low-hydrothermal conditions in sizes up to 0.3 mm. The structures were solved from CCD X-ray single-crystal data and refined toR= 0.033 and 0.019, respectively.Cu(OH)F: space groupP21/a,Z= 4,a= 5.301(1) Å,b= 6.376(1) Å,c= 5.074(1) Å,β= 112.90(1)°, andV= 157.98(5) Å3.Cu3(OH)2F4: space groupP21/n,Z= 2,a= 5.501(1) Å,b= 4.766(1) Å,c= 8.462(1) Å,β= 92.28(1)°, andV= 221.68(7) Å3.In both compounds the copper atoms are 4 + 2 coordinated to their ligands (Jahn-Tellerdistortion). Cu(OH)F is isotypic to Cu(OH)Cl, forming layers of edge-sharing Cu(OH)3F3polyhedra, which are interconnected by hydrogen bonds. The structure of Cu3(OH)2F4is characterized by chains of edge-sharing Cu(OH)2F4polyhedra running along [1 0 0], which are linked to each other via corners to form a framework. Hydrogen bonds of the type O—H···F occur with O···F distances of 2.619 and 2.697 Å in Cu(OH)Fand Cu3(OH)2F4, respectively. The observed O—H stretching frequencies of 3129 and 3306 cm–1, respectively, in Raman spectra are in excellent agreement with expected values from distance — frequency correlations. Moreover, the pleochroism of the bands corresponds in both compounds to the O—H orientation found in the structure determination.
Crystal chemistry of lead oxide phosphates: crystal structures of Pb4O(PO4)2, Pb8O5(PO4)2 and Pb10(PO4)6O
Authors: Krivovichev Sergey V. , Burns Peter C. 
Published: December 2003

Abstract
Crystals of three Pb oxide phosphates, Pb4O(PO4)2, Pb8O5(PO4)2 and Pb10(PO4)6O, were synthesized from mixtures of PbO and NH4H2PO4 heated to 950 °C. The crystal structure of Pb4O(PO4)2 (monoclinic, P21/c, a = 9.4894(8), b = 7.1402(6), c = 14.4077(13) Å, β = 104.549(2)°, V = 944.91(14) Å3) was solved by direct methods and refined to R1 = 0.044 (wR = 0.103). It contains isolated OPb4 tetrahedra that are linked through Pb—O bonds to O atoms of PO4 tetrahedra. The crystal structure of Pb8O5(PO4)2 (monoclinic, C2/m, a = 10.6427(4), b = 10.2078(4), c = 14.3530(6) Å, β = 98.325(1)°, V = 1542.86(11) Å3) was solved by direct methods and refined to R1 = 0.032 (wR = 0.068). It is based upon a complex sheet with composition [O5Pb8]. The basic element of the sheet is a cluster of composition [O5Pb10] that consists of four OPb4 tetrahedra that share edges. The adjacent [O5Pb10] clusters are linked by sharing Pb atoms, resulting in sheets that are parallel to (001). The PO4 tetrahedra are located in the interlayers between the sheets. The crystal structure of Pb10(PO4)6O (hexagonal, P63/m, a = 9.8650(3), c = 7.4306(3) Å, V = 626.25(4) Å3) has been solved by direct methods and refined to R1 = 0.040 (wR = 0.106). Pb10(PO4)6O crystallizes with an apatite-type structure. The structure contains a single O atom that is not part of a PO4 tetrahedron; it has a site occupancy factor of 0.25 and is located on the 63 axis.
Synthesis, structural and spectral studies of N-p-methylbenzyliden-N-phenyl-p,p′-dimethoxybenzoyl acetic acid hydrazide
Authors: Ülkü D. , Arıcı C. , Ercan F. , Saçmacı M. , Sarıpınar E. , Akçamur Y. 
Published: December 2003

Abstract
The structure of the organic derivative of N-p-methylbenzyliden-N-phenyl-p,p′-dimethoxybenzoyl acetic acid hydrazide, [C32H28N2O5], has been determined by X-ray diffraction. The structure derived from the NMR spectroscopy, the IR spectra and elemental analysis is consistent with that of the X-ray diffraction. The compound crystalizes in the monoclinic system with space group P21/c, a = 16.234(1), b = 9.399(2), c = 19.389(1), β = 110.924(3)°, V = 2763.3(5) Å3 and Z = 4. In the crystal, there is one weak C—H…O type intermolecular hydrogen bond interaction.
Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(–)-1-phenyl-ethyl ammonium percholorate
Authors: Özbey Süheyla , Kaynak F. B. , Toğrul M. , Demirel N. , Hoşgören H. 
Published: December 2003

Abstract
A new type of inclusion complex, S(–)-1 phenyl ethyl ammonium percholorate complex of R-(–)-2-ethyl - N - benzyl - 4, 7, 10, 13 - tetraoxa -1- azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group P21 with cell dimensions a = 10.0000(8), b = 12.281(2), c = 12.331(1)Å, β = 102.052(7), Z = 2 The host-guest complex is held together by a strong system of hydrogen bonds between the two protons of the ammonium ion as well as the nitrogen and four oxygen atoms of the crown ether The C—O and C—C distances of the 15-membered ring average 1.418 and 1.501 Å while the O—C—C and C—O—C angles average 110.2 and 113.3°. The average N—C distance is 1.476 Å.
Crystal structure of the K, Ti analogue of ilímaussite-(Ce), (Ba,K,Na,Ca)11–12(REE,Fe,Th)4(Ti,Nb)6(Si6O18)4(OH)12·4.5 H2O: revision of structure model and structural formula
Authors: Krivovichev Sergey V. , Yakovenchuk V. N. , Armbruster Th. , Pakhomovskiy Y. A. , Depmeier W. 
Published: December 2003

Abstract
The crystal structure of the K, Ti analogue of il¡maussite-(Ce), (Ba,K,Na,Ca)11–12(REE,Fe,Th)4(Ti,Nb)6(Si6O18)4(OH)12·4.5 H2O, from the Yukspor mountain, Khibiny massif, Kola peninsula, Russia, has been solved by direct methods and refined to R
1 = 0.077 on the basis of 1762 reflections with |F
o| ≥ 4σ
F. The mineral is rhombohedral, R32, a = 10.708(2), c = 60.073(11) Å, V = 5965.2(17) Å3. The structure is based upon a heteropolyhedral framework that consists of layers of corner-linked polyhedra. The SiO4 tetrahedra share corners to form 6-membered rings which are further interlinked via REEO6 trigonal prisms and Tiφ
6 octahedra (φ = O, OH). The obtained structure model is different from that recently reported by Rastsvetaeva et al. (2003) which is considered incorrect.
Analytic expressions for the vertex coordinates of quasiperiodic lattices
Authors: Naumis G. G. , Aragón J. L. 
Published: December 2003

Abstract
Using the generalized dual method, closed analytical expressions for the coordinates of quasiperiodic lattices, derived from periodic or quasiperiodic grids, are given. The obtained formulae constitute a useful and practical tool to generate and perform calculations in quasi periodic structures.
The hydrogen bond system of Mn-leonite: neutron diffraction results in comparison with IR spectroscopic data
Authors: Hertweck B. , Libowitzky E. , Schultz A. J. 
Published: December 2003

Abstract
Single-crystal Time-Of-Flight (TOF) neutron diffraction data of Mn-leonite, K2Mn(SO4)2·4 H2O, were obtained at 110, 185 and 295 K. Two reversible phase transitions at low temperatures have been previously confirmed by optical, calorimetric, and X-ray data. The cause for the phase transitions of Mn-leonite is a dynamic disorder of sulphate groups at room temperature (C2/m), that freeze to an ordered structure (I2/a) at 205(1) K. At 169(1) K the crystal structure switches to another ordered phase (P21/a).In general, the investigation by neutron diffraction confirms the structures of the three phases and, in addition, reveals the changes of the hydrogen bond configurations which influence the cooperative arrangement of the tetrahedra during the two successive phase transitions observed in Mn-leonite. IR spectroscopic measurements in the range of the O—H stretching frequencies yield a broad absorption band at ~3200 cm–1 that can only be resolved at low temperatures. A distance-frequency plot, calculated from the experimental data of low temperature neutron diffraction and IR spectroscopy is in agreement with correlation data from literature.
High pressure mixed alkali disilicates in the system Na2— xKxSi2O5: hydrothermal synthesis and crystal structures of NaKSi2O5-II and Na0.67K1.33Si2O5
Authors: Rakić S. , Kahlenberg V. , Schmidt B. C. 
Published: December 2003

Abstract
Single crystal growth experiments for NaKSi2O5 and Na0.67K1.33Si2O5 have been successfully performed by hydrothermal crystallization of two glasses at 500°C and 1 kbar during 24 hours. For a glass with a Na : K ratio of 1 : 1 a previously unknown NaKSi2O5 modification named phase II was obtained. The structure of NaKSi2O5-II has been solved from a single crystal diffraction data set and refined to a residual of R(|F|)= 0.032 for 1186 independent reflections. The compound is monoclinic with space group P21/c (a = 4.852(1) Å, b = 13.594(2) Å, c = 7.463(1) Å, β = 91.20(2)° V = 492.1(2) Å3, Mr
= 198.27 u, Z = 4, Dx
= 2.68 g/cm3, μ(MoKα
) = 1.58 mm–1) and belongs to the group of double chain silicates. Individual double chains can be described as being built by the condensation of zweier single chains of SiO4-tetrahedra running parallel to the a-axis. Each chain contains four-membered rings. Alkali-atoms are 6- and 8-fold coordinated by the oxygen ligands. NaKSi2O5-II is isotypic with the structure of NaRbSi2O5 which has been synthesized at room-pressure. Hydrothermal treatment of a second glass with composition Na0.5K1.5Si2O5 resulted in the formation of single-crystalline material of Na0.67K1.33Si2O5, slightly Na-richer than the starting composition. The platy crystals showed twinning by pseudo-merohedry, a feature we took account of by separating the reflections from the different twin individuals during the data collection. Structure solution has been accomplished by direct methods. The subsequent refinement converged to a residual of R(|F|) = 0.037 for 1543 independent reflections. The compound is mono clinic as well with space group I2/a (a = 12.731(2) Å, b = 7.321(1) Å, c = 17.827(3) Å, β = 100.85(2)° V = 1631.9(6) Å3, Mr
= 206.32 u, Z = 12, Dx
= 2.53 g/cm3, μ(MoKα
) = 1.78 mm–1) and belongs to the group of single layer silicates. A single layer consists of four-, six- and eight-membered rings, which are parallel to (100), and can be described as being built by the condensation of unbranched dreier single chains running along the b-axis. The stacking of the layers results in a three-dimensional structure in which the alkali cations reside between the layers for charge compensation. The distribution of the alkali atoms among the three crystallographically different positions M(1), M(2) and M(3) shows a definite preference of the larger potassium for the M(1) and M(2) site; the M(3) site is K-free. The alkali-atoms are 5- and 6- fold coordinated by the oxygen atoms. The geometrical and topological features of the single tetrahedral sheets in Na0.67K1.33Si2O5 are very similar to those observed in the phase I of NaKSi2O5. Differences can be attributed to different ways of stacking of adjacent sheets, and different sequences of up and down pointing tetrahedra within the rings.