(IUCr) Contents for Acta Crystallographica Section B Vol. 55 Part 4 (August 1999)

Acta Cryst. (1999). B55, 459-466 [ doi:10.1107/S0108768198017984 ]

Structures des phases paraélectrique et ferroélectrique de Pb₂KNb₅O₁₅

Ph. Sciau, G. Calvarin and J. Ravez

Synopsis: The paraelectric phase of Pb₂KNb₅O₁₅ has a tetragonal tungsten-bronze-like structure above the Curie temperature (T_C = 730 K). Below T_C the structure is slightly distorted (orthorhombic) and the phase is both ferroelectric and ferroelastic. A structural study of both phases by X-ray and neutron powder diffraction is presented.

Online August 1999

Acta Cryst. (1999). B55, 467-483 [ doi:10.1107/S0108768199000452 ]

Cluster configurations in modulated EuV_xMo_8±yO₁₄ crystals

H. Leligny, D. Grebille, P. Roussel, Ph. Labbé, M. Hervieu, B. Raveau, J. Tortelier and P. Gougeon

Synopsis: The modulated structures of three crystals of EuV_xMo_8±yO₁₄ with different compositions and different modulation waves are studied and compared. The action of the modulation on the distribution and the geometry of the different types of metallic clusters is also studied. Evidence is presented for new types of Mo₉ and Mo₁₀ metallic clusters, formed by capping three or four faces of the octahedral Mo₆ units, and strong metallic bonds between the clusters are implied in some unit cells of the three crystals.

Online August 1999

Acta Cryst. (1999). B55, 484-493 [ doi:10.1107/S0108768199001214 ]

Crystal structure, compressibility and possible phase transitions in $\boldvarepsilon$ -FeSi studied by first-principles pseudopotential calculations

L. Vocadlo, G. D. Price and I. G. Wood

Synopsis: Investigation of the relative stability of the FeSi structure and of some hypothetical polymorphs by first-principles pseudopotential calculations has shown that the observed distortion of the FeSi structure from its idealized form is essential for its stability. It is predicted that FeSi having a CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 13 GPa.

Online August 1999

Acta Cryst. (1999). B55, 494-506 [ doi:10.1107/S0108768199003730 ]

Systematic prediction of new inorganic ferroelectrics in point group 4

S. C. Abrahams

Synopsis: Approximately 40% of the crystal structures in point group 4 of the current release of the Inorganic Crystal Structure Database are found to satisfy the structural criteria for potential ferroelectricity. Each prediction of ferroelectricity is associated with a probable phase transition, not all of which are necessarily subgroup-supergroup transitions.

Online August 1999

Acta Cryst. (1999). B55, 507-516 [ doi:10.1107/S0108768199003845 ]

A TEM study of long-period mica polytypes: determination of the stacking sequence of oxybiotite by means of atomic resolution images and Periodic Intensity Distribution (PID)

T. Kogure and M. Nespolo

Synopsis: The stacking sequences of long-period polytypes (including a mixed-rotation 36-layer polytype) of oxybiotite mica have been unambiguously determined by the combination of atomic resolution images recorded down two zone axes and periodic intensity distributions in electron diffraction patterns using TEM.

Online August 1999

Acta Cryst. (1999). B55, 517-524 [ doi:10.1107/S0108768199003614 ]

Structure determination of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate by powder diffraction

H. Ehrenberg, B. Hasse, K. Schwarz and M. Epple

Synopsis: The polarizing effect of the small lithium cations determines the crystal structures of three lithium halogenoacetates and is most likely responsible for the absence of the solid-state polymerizability that is found for most other halogenoacetates.

Online August 1999

Acta Cryst. (1999). B55, 525-529 [ doi:10.1107/S010876819900018X ]

Single-crystal structure analysis of a novel aryl phosphinate diglycidyl ether

C.-S. Cho, W.-B. Liau and L.-W. Chen

Synopsis: The crystal structure of novel 10-[2,5-bis(2,3-epoxy-1-propoxy)phenyl]-9-oxa-10-phosphaphenanthren-10-one has been studied by single-crystal X-ray diffraction. The NMR chemical shifts of the protons of the glycidyl group close to the aryl phosphinate group are reduced by the `ring-current effect'.

Online August 1999

Acta Cryst. (1999). B55, 530-542 [ doi:10.1107/S0108768199000348 ]

Packing similarities of three isosteric molecules: 4,5-dichlorophthalic anhydride, 4,5-dibromophthalic anhydride and 5,6-dichlorobenzfurazan 1-oxide, including three polymorphs of 5,6-dichlorobenzfurazan 1-oxide

C. R. Ojala, W. H. Ojala, D. Britton and J. Z. Gougoutas

Synopsis: 4,5-Dichlorophthalic anhydride (CPA), 5,6-dichlorobenzfurazan 1-oxide (CBF) and 4,5-dibromophthalic anhydride (BPA) are approximately isosteric. CBF has three polymorphic forms. Polymorph A of CBF is isomorphous with CPA. Polymorph C of CBF and BPA are both pseudo-isomorphous with CPA, but in different ways.

Online August 1999

Acta Cryst. (1999). B55, 543-553 [ doi:10.1107/S0108768199001202 ]

Modelling the crystal structure of the 2-hydronitronylnitroxide radical (HNN): observed and computer-generated polymorphs

G. Filippini, A. Gavezzotti and J. J. Novoa

Synopsis: The crystal structures of two polymorphs of the title compound are analyzed by packing energy criteria. Other unobserved polymorphic crystal structures are generated using a polymorph predictor package and three different force fields, one of which is without explicit Coulomb-type terms. The X-ray structure of the $\alpha$ polymorph was found to be among the most stable ones by the polymorph predictor, even using the chargeless force field.

Online August 1999

Acta Cryst. (1999). B55, 554-562 [ doi:10.1107/S010876819900213X ]

Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile (C₇H₁₁N₅O₂) and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate (C₆H₆N₆O₄·H₂O) from X-ray, synchrotron and neutron powder diffraction data

V. V. Chernyshev, A. N. Fitch, E. J. Sonneveld, A. I. Kurbakov, V. A. Makarov and V. A. Tafeenko

Synopsis: The unknown crystal and molecular structures of two organic compounds have been determined from X-ray, synchrotron and neutron powder diffraction data using various methods. The results obtained demonstrate the high level of reproducibility and reliability of various powder software and equipment.

Online August 1999

Acta Cryst. (1999). B55, 563-572 [ doi:10.1107/S0108768199002128 ]

Topological analysis of the electron density in hydrogen bonds

E. Espinosa, M. Souhassou, H. Lachekar and C. Lecomte

Synopsis: Topological analysis of the electron density at the hydrogen bond critical point (CP) on a large number of crystals studied by experimental [X - X and X - (X + N)] methods has been investigated. A new classification of the hydrogen bond is proposed involving the [lambda] ₃ electron density curvature along the bonding direction.

Online August 1999

Acta Cryst. (1999). B55, 573-590 [ doi:10.1107/S0108768199002645 ]

Crystal engineering using bisphenols: interwoven ladders, sheet and framework structures in the binary adducts of 4,4'-sulfonyldiphenol with pyrazine (2/1), 4,4'-bipyridyl (1/1), trans-1,2-bis(4-pyridyl)ethene (1/1), 1,2-bis(4-pyridyl)ethane (1/1) and 4,4'-trimethylenedipyridine (1/1), and in 4,4'-sulfonyldiphenol-4,4'-trimethylenedipiperidine-water (2/2/1)

G. Ferguson, C. Glidewell, R. M. Gregson and E. S. Lavender

Synopsis: The 2:1 adduct of 4,4'-sulfonyldiphenol and pyrazine takes the form of continuously interwoven molecular ladders; the 1:1 adducts of 4,4'-sulfonyldiphenol with 4,4'-bipyridyl, 1,2-bis(4-pyridyl)ethene, 1,2-bis(4-pyridyl)ethane and 4,4'-trimethylenedipyridine all consist of chains, further cross-linked by C-HO hydrogen bonds. The aquated adduct with 4,4'-trimethylenedipiperidine is a salt in which the components form a hydrogen-bonded three-dimensional framework.

Online August 1999

Acta Cryst. (1999). B55, 591-600 [ doi:10.1107/S0108768199002657 ]

Crystal engineering using bisphenols and trisphenols. Complexes with 1,10-phenanthroline: hydrogen-bonded chains in adducts with 4,4'-biphenol (1/1) and 4,4'-sulfonyldiphenol (2/3), - stacked chains in the (1/2) adduct with 4,4'-thiodiphenol, and pairwise-interwoven nets in 1,1,1-tris(4-hydroxyphenyl)ethane-1,10-phenanthroline-methanol (1/1/1)

G. Ferguson, C. Glidewell and E. S. Lavender

Synopsis: In its 1:1 adduct with 4,4'-biphenol, 1,10-phenanthroline act as a builder of hydrogen-bonded chains; in its 1:2 adduct with 4,4'-thiodiphenol the diamine acts as a terminator of such chains, and in its 2:3 adduct with 4,4'-sulfonyldiphenol, both roles are manifest. In the methanol-solvated 1:1:1 adduct with 1,1,1-tris(4-hydroxyphenyl)ethane the 1,10-phenanthroline units act as chain terminators and the structure contains pairwise-interwoven nets.

Online August 1999

Acta Cryst. (1999). B55, 601-606 [ doi:10.1107/S0108768199003468 ]

The single-crystal structure of the organic superconductor _CO-(BEDT-TTF)₂I₃ from a powder grain

D. Madsen, M. Burghammer, S. Fiedler and H. Müller

Synopsis: A synchrotron radiation study has been carried out on a single crystal of dimensions 12 × 10 × 2 µm of the organic superconductor [beta] _CO-(BEDT-TTF)₂I₃. The triiodide site population deviates slightly from unity and the conformations and occupancies of the disordered ethylene groups have been determined.

Online August 1999

Acta Cryst. (1999). B55, 607-616 [ doi:10.1107/S0108768199003948 ]

Absolute configurations of Emycin D, E and F; mimicry of centrosymmetric space groups by mixtures of chiral stereoisomers

M. Walker, E. Pohl, R. Herbst-Irmer, M. Gerlitz, J. Rohr and G. M. Sheldrick

Synopsis: A mixture of stereoisomers can be misinterpreted as a disordered centrosymmetric structure, but only the ordered structure in a chiral space group is consistent with the anomalous dispersion and chemical evidence.

Online August 1999

Acta Cryst. (1999). B55, 617-625 [ doi:10.1107/S0108768199005091 ]

A mediated hydrogen bond in an -hydroxycarboxyl group: X-ray structure of (R,R)-N-methyltartramic acid monohydrate and an ab initio study of model systems

U. Rychlewska, A. Szarecka, J. Rychlewski and R. Motala

Synopsis: A mediated three-centre hydrogen bond is one of the packing motifs involving the [alpha] -hydroxycarbonyl moiety in (R,R)-tartaric acid and (R,R)-N-methyltartramic acid monohydrate. The stability of such bonding in model complexes is studied via theoretical calculations.

Online August 1999

short communications

Acta Cryst. (1999). B55, 626 [ doi:10.1107/S0108768199006679 ]

Anhydrous ammonioguanidinium(2+) and dihydrated bis[aminoguanidinium(1+)] hexafluorosilicates: new co-products of preparing ferroelectric ammonioguanidinium(2+) hexafluorozirconate. Erratum

C. R. Ross, M. R. Bauer, R. M. Nielson and S. C. Abrahams

Synopsis: An error in printing in the paper by Ross et al. [Acta Cryst. (1999), B55, 246-254] is reported.

Online August 1999

Acta Crystallographica Section B

Structural Science

Volume 55, Part 4 (August 1999)

research papers

Structures des phases paraélectrique et ferroélectrique de Pb₂KNb₅O₁₅

Ph. Sciau, G. Calvarin and J. Ravez

Cluster configurations in modulated EuV_xMo_8±yO₁₄ crystals

H. Leligny, D. Grebille, P. Roussel, Ph. Labbé, M. Hervieu, B. Raveau, J. Tortelier and P. Gougeon

Crystal structure, compressibility and possible phase transitions in $\boldvarepsilon$ -FeSi studied by first-principles pseudopotential calculations

L. Vocadlo, G. D. Price and I. G. Wood

Systematic prediction of new inorganic ferroelectrics in point group 4

S. C. Abrahams

A TEM study of long-period mica polytypes: determination of the stacking sequence of oxybiotite by means of atomic resolution images and Periodic Intensity Distribution (PID)

T. Kogure and M. Nespolo

Structure determination of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate by powder diffraction

H. Ehrenberg, B. Hasse, K. Schwarz and M. Epple

Single-crystal structure analysis of a novel aryl phosphinate diglycidyl ether

C.-S. Cho, W.-B. Liau and L.-W. Chen

Packing similarities of three isosteric molecules: 4,5-dichlorophthalic anhydride, 4,5-dibromophthalic anhydride and 5,6-dichlorobenzfurazan 1-oxide, including three polymorphs of 5,6-dichlorobenzfurazan 1-oxide

C. R. Ojala, W. H. Ojala, D. Britton and J. Z. Gougoutas

Modelling the crystal structure of the 2-hydronitronylnitroxide radical (HNN): observed and computer-generated polymorphs

G. Filippini, A. Gavezzotti and J. J. Novoa

Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile (C₇H₁₁N₅O₂) and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate (C₆H₆N₆O₄·H₂O) from X-ray, synchrotron and neutron powder diffraction data

V. V. Chernyshev, A. N. Fitch, E. J. Sonneveld, A. I. Kurbakov, V. A. Makarov and V. A. Tafeenko

Topological analysis of the electron density in hydrogen bonds

E. Espinosa, M. Souhassou, H. Lachekar and C. Lecomte

G. Ferguson, C. Glidewell, R. M. Gregson and E. S. Lavender

G. Ferguson, C. Glidewell and E. S. Lavender

The single-crystal structure of the organic superconductor _CO-(BEDT-TTF)₂I₃ from a powder grain

D. Madsen, M. Burghammer, S. Fiedler and H. Müller

Absolute configurations of Emycin D, E and F; mimicry of centrosymmetric space groups by mixtures of chiral stereoisomers

M. Walker, E. Pohl, R. Herbst-Irmer, M. Gerlitz, J. Rohr and G. M. Sheldrick

A mediated hydrogen bond in an -hydroxycarboxyl group: X-ray structure of (R,R)-N-methyltartramic acid monohydrate and an ab initio study of model systems

U. Rychlewska, A. Szarecka, J. Rychlewski and R. Motala

short communications

Anhydrous ammonioguanidinium(2+) and dihydrated bis[aminoguanidinium(1+)] hexafluorosilicates: new co-products of preparing ferroelectric ammonioguanidinium(2+) hexafluorozirconate. Erratum

C. R. Ross, M. R. Bauer, R. M. Nielson and S. C. Abrahams


	Cover illustration: An infinite hydrogen-bonded sheet in guanidinium trifluoromethanesulfonate. Courtesy of C. B. Aakeröy [Acta Cryst. (1997), B53, 569-586; structure determined by V. A. Russell, M. C. Etter & M. D. Ward].

Acta Crystallographica Section B

Structural Science

Volume 55, Part 4 (August 1999)

research papers

Structures des phases paraélectrique et ferroélectrique de Pb2KNb5O15

Ph. Sciau, G. Calvarin and J. Ravez

Cluster configurations in modulated EuVxMo8±yO14 crystals

H. Leligny, D. Grebille, P. Roussel, Ph. Labbé, M. Hervieu, B. Raveau, J. Tortelier and P. Gougeon

Crystal structure, compressibility and possible phase transitions in -FeSi studied by first-principles pseudopotential calculations

L. Vocadlo, G. D. Price and I. G. Wood

Systematic prediction of new inorganic ferroelectrics in point group 4

S. C. Abrahams

A TEM study of long-period mica polytypes: determination of the stacking sequence of oxybiotite by means of atomic resolution images and Periodic Intensity Distribution (PID)

T. Kogure and M. Nespolo

Structure determination of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate by powder diffraction

H. Ehrenberg, B. Hasse, K. Schwarz and M. Epple

Single-crystal structure analysis of a novel aryl phosphinate diglycidyl ether

C.-S. Cho, W.-B. Liau and L.-W. Chen

Packing similarities of three isosteric molecules: 4,5-dichlorophthalic anhydride, 4,5-dibromophthalic anhydride and 5,6-dichlorobenzfurazan 1-oxide, including three polymorphs of 5,6-dichlorobenzfurazan 1-oxide

C. R. Ojala, W. H. Ojala, D. Britton and J. Z. Gougoutas

Modelling the crystal structure of the 2-hydronitronylnitroxide radical (HNN): observed and computer-generated polymorphs

G. Filippini, A. Gavezzotti and J. J. Novoa

Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile (C7H11N5O2) and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate (C6H6N6O4·H2O) from X-ray, synchrotron and neutron powder diffraction data

V. V. Chernyshev, A. N. Fitch, E. J. Sonneveld, A. I. Kurbakov, V. A. Makarov and V. A. Tafeenko

Topological analysis of the electron density in hydrogen bonds

E. Espinosa, M. Souhassou, H. Lachekar and C. Lecomte

G. Ferguson, C. Glidewell, R. M. Gregson and E. S. Lavender

G. Ferguson, C. Glidewell and E. S. Lavender

The single-crystal structure of the organic superconductor CO-(BEDT-TTF)2I3 from a powder grain

D. Madsen, M. Burghammer, S. Fiedler and H. Müller

Absolute configurations of Emycin D, E and F; mimicry of centrosymmetric space groups by mixtures of chiral stereoisomers

M. Walker, E. Pohl, R. Herbst-Irmer, M. Gerlitz, J. Rohr and G. M. Sheldrick

A mediated hydrogen bond in an -hydroxycarboxyl group: X-ray structure of (R,R)-N-methyltartramic acid monohydrate and an ab initio study of model systems

U. Rychlewska, A. Szarecka, J. Rychlewski and R. Motala

short communications

Anhydrous ammonioguanidinium(2+) and dihydrated bis[aminoguanidinium(1+)] hexafluorosilicates: new co-products of preparing ferroelectric ammonioguanidinium(2+) hexafluorozirconate. Erratum

C. R. Ross, M. R. Bauer, R. M. Nielson and S. C. Abrahams

Structures des phases paraélectrique et ferroélectrique de Pb₂KNb₅O₁₅

Cluster configurations in modulated EuV_xMo_8±yO₁₄ crystals

Crystal structure, compressibility and possible phase transitions in $\boldvarepsilon$ -FeSi studied by first-principles pseudopotential calculations

Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile (C₇H₁₁N₅O₂) and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate (C₆H₆N₆O₄·H₂O) from X-ray, synchrotron and neutron powder diffraction data

The single-crystal structure of the organic superconductor _CO-(BEDT-TTF)₂I₃ from a powder grain