Structural Chemistry

Structural Mineralogy and Inorganic Crystal Chemistry. By Sergey V. Krivovichev. St Petersburg University Press, 2009. Pp. 398. (Hardbound) Price unknown. ISBN 978-5-288-05004-6.

Publication Date: 2012 Feb PMID: 22267566
Authors: Ferraris, G.
Journal: Acta Crystallogr B

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Notes for authors 2012.

Publication Date: 2012 Feb PMID: 22267565
Authors:
Journal: Acta Crystallogr B

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Water channel structure of bassanite at high air humidity: crystal structure of CaSO(4).0.625H(2)O. Corrigendum.

Publication Date: 2012 Feb PMID: 22267564
Authors: Schmidt, H. - Paschke, I. - Freyer, D. - Voigt, W.
Journal: Acta Crystallogr B

The correspondence author in the paper by Schmidt et al. [(2011), Acta Cryst. B67, 467-475] is corrected.

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Lattice constants and thermal expansion of H(2)O and D(2)O Ice Ih between 10 and 265 K. Addendum.

Publication Date: 2012 Feb PMID: 22267563
Authors: Rottger, K. - Endriss, A. - Ihringer, J. - Doyle, S. - Kuhs, W. F.
Journal: Acta Crystallogr B

In a previous paper we reported the lattice constants and thermal expansion of normal and deuterated ice Ih [Rottger et al. (1994). Acta Cryst. B50, 644-648]. Synchrotron X-ray powder diffraction data were used to obtain the lattice constants and unit-cell volumes of H(2)O and D(2)O ice Ih in the temperature range 15-265 K. A polynomial expression was given for the unit-cell volumes. It turns out that the coefficients quoted have an insufficient number of digits to faithfully reproduce the volume cell data. Here we provide a table with more significant digits. Moreover, we also provide the coefficients of a polynomial fit to the previously published a and c lattice constants of normal and deuterated ice Ih for the same temperature range.

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Revision of the Mg(ClO(4))(2).4H(2)O crystal structure.

Publication Date: 2012 Feb PMID: 22267562
Authors: Solovyov, L. A.
Journal: Acta Crystallogr B

A revision is presented of the restrained Rietveld analysis of the crystal structure of magnesium perchlorate tetrahydrate, Mg(ClO(4))(2).4H(2)O, recently published by Robertson & Bish [(2010), Acta Cryst. B66, 579-584]. The actual symmetry of the material is shown to be C2/m. The corrected structure model is refined by the derivative difference method [Solovyov (2004). J. Appl. Cryst. 37, 743-749], anisotropically for all non-H atoms and isotropically for two independent H atoms without restraints.

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Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs.

Publication Date: 2012 Feb PMID: 22267561
Authors: Chan, E. J. - Goossens, D. J.
Journal: Acta Crystallogr B

Single-crystal diffuse X-ray scattering from paracetamol polymorphs is successfully calculated with Monte Carlo (MC) models that are used to simulate the crystals. In order to obtain the correct model appropriate force constants are required that describe the interatomic potentials used in the MC algorithm. Coefficients for an empirical `Buckingham'-type formula are used to determine these force constants. These coefficients are subsequently refined using the least-squares method and are found to converge on similar values for both polymorphic forms. An investigation of the correlation space generated from each model provides what would be expected given that strong displacive correlations exist between the molecules comprising the densely hydrogen-bonded layers. More disordered motions between these layers are present in the model for form (II) as opposed to form (I). An investigation into the peculiarities of librational disorder was also conducted, however, correlation values turn out to be so small that any structural information concerning librational correlation is inconclusive. The purpose of this experiment was to identify if the diffuse scattering features could provide further insight into understanding the physical reasoning behind the metastability of form (II). The form (II) --> (I) phase transition is also not currently well understood and usually phase transitional information can be obtained from pronounced diffuse scattering features. Since the diffuse scattering is modelled adequately using harmonic potentials it is our conjecture that the `diffuse' is essentially thermal in origin and does not afford any extra information about the form (II) --> (I) phase transition.

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Hydrogen-bridged chelate ring-assisted pi-stacking interactions.

Publication Date: 2012 Feb PMID: 22267560
Authors: Karabiyik, H. - Karabiyik, H. - Ocak Iskeleli, N.
Journal: Acta Crystallogr B

A salicylideneaniline (SA) derivative, (6Z)-6-({[2-(hydroxymethyl)phenyl]amino}methylidene)-3,5-dimethoxycyclohex a-2,4-dien-1-one monohydrate, has an increased aromaticity within its hydrogen-bridged chelate ring owing to its NH character. In the reported crystal structure, nonconventional pi-stacking interactions, which are referred to as hybrid pi-stacking interactions, are observed between a quasiaromatic chelate ring, formed as a result of the resonance-assisted intramolecular hydrogen bond and ordinary aromatic rings. Besides, pi-stacking interactions are also seen between two hydrogen-bridged quasiaromatic chelate rings, which are referred to as pure pi-stacking interactions. A CSD search has revealed that both kinds of interactions are frequently observed in molecular crystals of SA derivatives in fully or partially NH tautomeric form, and aromaticity levels of certain fragments of SA derivatives have dramatic effects on their stacking arrangements. These interactions are distinguished from the usual pi...pi interactions by their formation character, i.e. both sigma- and pi-deficient and sigma-deficient character of pure interactions is more pronounced than that of the hybrid ones.

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An order-disorder phase transition in the structure of C(60).4benzene.

Publication Date: 2012 Feb PMID: 22267559
Authors: Olmstead, M. M. - Balch, A. L. - Lee, H. M.
Journal: Acta Crystallogr B

A reversible, broad, order-disorder phase transition in the structure of C(60).4benzene has been observed to take place with an inflection point at 134 K. In the low-temperature structure fullerene disorder is removed, although the average atomic displacement parameters differ for the two C(60) molecules in the asymmetric unit. Some benzene disorder persists, even at 13 K.

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Face-to-face stacking of quinoid rings of alkali salts of bromanilic acid.

Publication Date: 2012 Feb PMID: 22267558
Authors: Molcanov, K. - Kojic-Prodic, B.
Journal: Acta Crystallogr B

A series of alkali salts of hydrogen bromanilic acid trihydrates (K(+), Rb(+) and Cs(+), potassium, rubidium and caesium 2,5-dibromo-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate trihydrate), bromanilic acid tetrahydrate (Na(+), disodium 2,5-dibromo-3,6-dioxocyclohexa-1,4-diene-1,4-diolate tetrahydrate) and bromanilic acid dihydrates (K(+), Rb(+) and Cs(+), dipotasium, dirubidium and dicaesium 2,5-dibromo-3,6-dioxocyclohexa-1,4-diene-1,4-diolate dihydrate) were prepared and studied by single-crystal X-ray diffraction. Their crystal packings are dominated by quinoid ring stacking. The monoanionic quinoid rings pack face-to-face without offset and with short centroid separations (3.25-3.30 A), while the dianionic rings form offset stacks (1.4-1.8 A) with a larger centroid separation (3.8-4.1 A).

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Structural phase transition to disorder low-temperature phase in [Fe(ptz)(6)](BF(4))(2) spin-crossover compounds.

Publication Date: 2012 Feb PMID: 22267557
Authors: Kusz, J. - Zubko, M. - Neder, R. B. - Gutlich, P.
Journal: Acta Crystallogr B

In the spin-crossover compound [Fe(ptz)(6)](BF(4))(2) (where ptz=1-n-propyltetrazole) six different phases are observed. When a single crystal is slowly cooled from high temperatures to those below 125 K, the reflections broaden into diffuse maxima and split into two maxima along the c* direction [Kusz, Gutlich & Spiering (2004). Top. Curr. Chem. 234, 129-153]. As both maxima are broad along the c* direction, the short-range order exists only along the c direction and in the ab plane the structure remains long-range ordered. In this disordered phase additional satellite reflections appear. Upon heating above 135 K, the diffuse maxima return to their previous shape and this process is completely reversible. Rapidly cooled samples, on the other hand, do not show such splitting and the symmetry remains R\bar 3, despite a jump in lattice parameters. We use a special technique to analyse the disorder model of the slowly cooled samples, which consists of layered domains shifted in the hexagonal ab plane. The low-spin disordered phase was solved in a novel approach to accommodate the very unusual twinning and refined in the non-standard space group C\bar 1. In contrast to the ordered low-spin phase, the Fe ion is in a non-centrosymmetric coordination polyhedron and two of the six propyl groups change their conformation.

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Polymorphism of li(2)zn(3).

Publication Date: 2012 Feb PMID: 22267556
Authors: Pavlyuk, V. - Chumak, I. - Ehrenberg, H.
Journal: Acta Crystallogr B

Crystal structures of low- and high-temperature modifications of the binary phase Li(2)Zn(3) were determined by single-crystal X-ray diffraction techniques. The low-temperature modification is a disordered variant of Li(5)Sn(2), space group R\bar 3m (No. 166). The high-temperature modification crystallizes as an anti-type to Li(5)Ga(4), space group P\bar 3m1 (No. 164). Two polymorphs can be described as derivative structures to binary Li(5)Ga(4), Li(5)Sn(2), Li(13)Sn(5), Li(8)Pb(3), CeCd(2) and CdI(2) phases which belong to class 2 with the parent W-type in Krypyakevich's classification. All atoms in both polymorphs are coordinated by rhombic dodecahedra (coordination number CN = 14) like atoms in related structures. The Li(2)Zn(2.76) (for the low-temperature phase) and Li(2)Zn(2.82) (for the high-temperature phase) compositions were obtained after structure refinements. According to electronic structure calculations using the tight-binding-linear muffin-tin orbital-atomic spheres approximations (TB-LMTO-ASA) method, strong covalent Sn-Sn and Ga-Ga interactions were established in Li(5)Sn(2) and Li(5)Ga(4), but no similar Zn-Zn interactions were observed in Li(2)Zn(3).

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Structure maps for A(I)(4)A(II)(6)(BO(4))(6)X(2) apatite compounds via data mining.

Publication Date: 2012 Feb PMID: 22267555
Authors: Balachandran, P. V. - Rajan, K.
Journal: Acta Crystallogr B

This paper describes a method to identify key crystallographic parameters that can serve as strong classifiers of crystal chemistries and hence define new structure maps. The selection of this pair of key parameters from a large set of potential classifiers is accomplished through a linear data-dimensionality reduction method. A multivariate data set of known A(I)(4)A(II)(6)(BO(4))(6)X(2) apatites is used as the basis for the study where each A(I)(4)A(II)(6)(BO(4))(6)X(2) compound is represented as a 29-dimensional vector, where the vector components are discrete scalar descriptors of electronic and crystal structure attributes. A new structure map, defined using the two distortion angles alpha(AII) (rotation angle of A(II)-A(II)-A(II) triangular units) and psi(AIz = 0)(AI-O1) (angle the A(I)-O1 bond makes with the c axis when z = 0 for the A(I) site), is shown to classify apatite crystal chemistries based on site occupancy on the A, B and X sites. The classification is accomplished using a K-means clustering analysis.

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Structure of the new mineral sarrabusite, Pb(5)CuCl(4)(SeO(3))(4), solved by manual electron-diffraction tomography.

Publication Date: 2012 Feb PMID: 22267554
Authors: Gemmi, M. - Campostrini, I. - Demartin, F. - Gorelik, T. E. - Gramaccioli, C. M.
Journal: Acta Crystallogr B

The new mineral sarrabusite Pb(5)CuCl(4)(SeO(3))(4) has been discovered in the Sardinian mine of Baccu Locci, near Villaputzu. It occurs as small lemon-yellow spherical aggregates of tabular crystals (< 10 microm) of less than 100 microm in diameter. The crystal structure has been solved from and refined against electron diffraction of a microcrystal. Data sets have been measured by both a manual and an automated version of the new electron-diffraction tomography technique combined with the precession of the electron beam. The sarrabusite structure is monoclinic and consists of (010) layers of straight chains formed by alternating edge-sharing CuO(4)Cl(2) and PbO(8) polyhedra parallel to the c axis, which share corners laterally with two zigzag corner-sharing chains of PbO(6)Cl(2) and PbO(4)Cl(4) bicapped trigonal prisms. These blocks are linked together by SeO_3^{2-} flat-pyramidal groups.

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High-precision absolute lattice parameter determination of SrTiO(3), DyScO(3) and NdGaO(3) single crystals.

Publication Date: 2012 Feb PMID: 22267553
Authors: Schmidbauer, M. - Kwasniewski, A. - Schwarzkopf, J.
Journal: Acta Crystallogr B

The lattice parameters of three perovskite-related oxides have been measured with high precision at room temperature. An accuracy of the order of 10(-5) has been achieved by applying a sophisticated high-resolution X-ray diffraction technique which is based on the modified Bond method. The results on cubic SrTiO(3) [a = 3.905268 (98) A], orthorhombic DyScO(3) [a = 5.442417 (54), b = 5.719357 (52) and c = 7.904326 (98) A], and orthorhombic NdGaO(3) [a = 5.428410 (54), b = 5.498407 (55) and c = 7.708878 (95) A] are discussed in view of possible systematic errors as well as non-stoichiometry in the crystals.

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Structure of a new high-pressure-high-temperature modification of antimony(III) oxide, gamma-Sb(2)O(3), from high-resolution synchrotron powder diffraction data.

Publication Date: 2012 Feb PMID: 22267552
Authors: Orosel, D. - Dinnebier, R. E. - Blatov, V. A. - Jansen, M.
Journal: Acta Crystallogr B

A quenchable new high-pressure-high-temperature modification of antimony(III) oxide, gamma-Sb(2)O(3), has been obtained at hydrostatic pressures of 9-11 GPa and temperatures of 573-773 K. Its crystal structure has been determined from high-resolution synchrotron powder diffraction data. gamma-Sb(2)O(3) consists of three-dimensionally cross-linked infinite chains of SbO(3)E units (E = lone pair) with the chains forming tetragonal rod-packing. The underlying topology of gamma-Sb(2)O(3) (3,3T8) is found very rarely in inorganic structures; it is realised only for the polyanion [Si(4)O(4)N(6)](10-) that occurs in the Ce(4)(Si(4)O(4)N(6))O structure type. The structural relation to the two previously known polymorphs of Sb(2)O(3) at ambient pressure, valentinite and senarmontite is discussed.

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