(IUCr) Contents for Acta Crystallographica Section B Vol. 55 Part 3 (June 1999)

Acta Cryst. (1999). B55, 259-265 [ doi:10.1107/S0108768198011239 ]

Crystal lattice and phase transitions in Na₄TiP₂O₉ (NTP) and Na_4.5FeP₂O₈(O,F) (NFP) superionic conductors as a function of high pressures and temperatures

B. Maximov, M. Sirota, S. Werner and H. Schulz

Synopsis: The lattice dynamics of Na₄TiP₂O₉ (NTP) and Na_4.5FeP₂O₈(O,F) (NFP) crystals, which are superionic conductors with Na⁺-ion conductivity, were studied under high pressures. Lattice constants as functions of hydrostatic pressure were measured on a four-circle diffractometer using a high-pressure cell with diamond anvils.

Online June 1999

Acta Cryst. (1999). B55, 266-272 [ doi:10.1107/S0108768198012567 ]

Cation distribution and crystal chemistry of Y₃Al_5-xGa_xO₁₂ (0 x 5) garnet solid solutions

A. Nakatsuka, A. Yoshiasa and T. Yamanaka

Synopsis: Investigation of the cation distributions in Y₃Al_5-xGa_xO₁₂ (0 x 5) garnet solid solutions using single-crystal X-ray diffraction shows that Ga³⁺, which is larger than Al³⁺, preferentially occupies the tetrahedral site rather than the octahedral site, contrary to the effect of cation size. This peculiar cation distribution is most probably caused by both the strong covalency of the Ga-O bond and the need to decrease the neighbouring cation-cation repulsive force.

Online June 1999

Acta Cryst. (1999). B55, 273-284 [ doi:10.1107/S0108768198013536 ]

Electron density distribution and Madelung potential in -spodumene, LiAl(SiO₃)₂, from two-wavelength high-resolution X-ray diffraction data

S. Kuntzinger and N. E. Ghermani

Synopsis: The experimental electron density features derived from both high-resolution Mo K [alpha] and Ag K [alpha] X-ray diffraction data are compared for the natural mineral [alpha] -spodumene, LiAl(SiO₃)₂. The kappa-refinement atomic net charges have been used to calculate the Madelung potential. An estimate of the chemical formula electrostatic energy is given.

Online June 1999

Acta Cryst. (1999). B55, 285-296 [ doi:10.1107/S0108768198013573 ]

Single-crystal neutron diffraction study of -Cs₃(HSO₄)₂[H_2-x(S_xP_1-x)O₄] (x 0.5) at 15 K

S. M. Haile and W. T. Klooster

Synopsis: The structure of [beta] -Cs₃(HSO₄)₂[H_2-x(S_xP_1-x)O₄] has been studied by neutron diffraction methods and can be adequately described by two different models for the disorder on H and S/P atom sites. The disorder is responsible for the relatively high proton conductivity at room temperature.

Online June 1999

Acta Cryst. (1999). B55, 297-305 [ doi:10.1107/S0108768198013950 ]

Arrangement of C atoms in the SiC-C solid solution

O. O. Mykhaylyk and M. P. Gadzira

Synopsis: On the basis of microstructure characteristics (strain and crystallite size) and lattice parameters investigated by X-ray powder diffraction methods, a structural model for the SiC-C solid solution is proposed. The behaviour of the structure under high-pressure and high-temperature sintering and annealing in a vacuum is described.

Online June 1999

Acta Cryst. (1999). B55, 306-312 [ doi:10.1107/S0108768198014086 ]

Structures of Bi₁₄WO₂₄ and Bi₁₄MoO₂₄ from neutron powder diffraction data

C. D. Ling, R. L. Withers, J. G. Thompson and S. Schmid

Synopsis: The (isomorphous) structures of Bi₁₄WO₂₄ and Bi₁₄MoO₂₄ have been solved and refined using neutron powder diffraction data in the space group I4/m. The structure adheres closely to a fluorite-type [delta] -Bi₂O₃-related parent structure. The metal atoms are compositionally ordered. Substantial displacive disorder is evident around the W site, which appears to be coordinated by a highly disordered O-atom tetrahedron.

Online June 1999

Acta Cryst. (1999). B55, 313-320 [ doi:10.1107/S0108768198014268 ]

The crystal structure of Ca₇Zr₇Ta₆O₃₆ refined using synchrotron-radiation data

S. Schmid, J. G. Thompson, R. L. Withers, C. D. Ling, N. Ishizawa and S. Kishimoto

Synopsis: The crystal structure of Ca₇Zr₇Ta₆O₃₆ is solved and refined in space group Fddd using single-crystal X-ray diffraction data.

Online June 1999

Acta Cryst. (1999). B55, 321-326 [ doi:10.1107/S0108768198016759 ]

Synchrotron X-ray analysis of the electron density in HoFe₂

V. A. Streltsov and N. Ishizawa

Synopsis: The deformation electron density ( [Delta] [rho] ) for the HoFe₂ Laves compound obtained from synchrotron X-ray diffraction data shows excess electron density midway along the Ho-Ho, Ho-Fe and Fe-Fe contacts which challenges the conventional understanding of electron interactions in magnetic materials.

Online June 1999

Acta Cryst. (1999). B55, 327-332 [ doi:10.1107/S0108768198014414 ]

Determination of the site of incorporation of cobalt in CoZnPO-CZP by multiple-wavelength anomalous-dispersion crystallography

M. Helliwell, J. R. Helliwell, V. Kaucic, N. Zabukovec Logar, L. Barba, E. Busetto and A. Lausi

Synopsis: A five-wavelength MAD experiment conducted at ELETTRA Sincrotone, and subsequent crystallographic analysis, shows that substitution of cobalt in CoZnPO-CZP occurs primarily at one of the two sites, with an occupancy of 24-30%. Site-specific occupancies of as low as 12-15% should, in general, be discernible by this method.

Online June 1999

Acta Cryst. (1999). B55, 333-340 [ doi:10.1107/S0108768198016966 ]

Structural investigation of the negative-thermal-expansion material ZrW₂O₈

J. S. O. Evans, W. I. F. David and A. W. Sleight

Synopsis: The structure of the negative-thermal-expansion material ZrW₂O₈ has been determined by parametric Rietveld refinement of high-resolution neutron powder diffraction data collected at 260 temperatures between 2 and 520 K. Despite data collection times of just 5 min at each temperature, it is shown that full anisotropic refinement of the structure is possible.

Online June 1999

Acta Cryst. (1999). B55, 341-347 [ doi:10.1107/S0108768198018345 ]

Disparate atomic displacements in skutterudite-type LaFe₃CoSb₁₂, a model for thermoelectric behavior

B. C. Chakoumakos, B. C. Sales, D. Mandrus and V. Keppens

Synopsis: Mean-square atomic displacements in LaFe₃CoSb₁₂ show that the La atom exhibits an anomalously large displacement. The large-amplitude rattling of the La atom is linked to the dramatic decrease of the lattice thermal conductivity and this structure-property relationship offers a new paradigm for the exploration of thermoelectric materials.

Online June 1999

Acta Cryst. (1999). B55, 348-354 [ doi:10.1107/S0108768198018333 ]

The crystal structure of the B-site ordered complex perovskite Sr(Yb_0.5Nb_0.5)O₃

J. H. Yang, W. K. Choo, J. H. Lee and C. H. Lee

Synopsis: The room-temperature crystal structure of Sr(Yb_0.5Nb_0.5)O₃ is monoclinic and can be derived from a triclinic distortion of the prototype cubic cell. The ordering of the different species of B-site cation, Yb³⁺ and Nb⁵⁺, inherently causes a volume difference between the YbO₆ and NbO₆ octahedra. The triclinic distortion of the prototype cell is caused by a^-a^-c⁺ octahedral tilting of the two octahedra with differing volumes. This volume difference is shown to inevitably inhibit the rigid rotation of the octahedra.

Online June 1999

Acta Cryst. (1999). B55, 355-362 [ doi:10.1107/S0108768198018424 ]

Structure analysis of new homologous compounds Ga₂O₃(ZnO)_m (m = integer) by high-resolution analytical transmission electron microscopy

C. Li, Y. Bando, M. Nakamura, K. Kurashima and N. Kimizuka

Synopsis: The crystal structure of Ga₂O₃(ZnO)_m studied by high-resolution analytical transmission electron microscopy is reported.

Online June 1999

Acta Cryst. (1999). B55, 363-374 [ doi:10.1107/S0108768198010398 ]

Accurate charge densities in days - use of synchrotrons, image plates and very low temperatures

B. B. Iversen, F. K. Larsen, A. A. Pinkerton, A. Martin, A. Darovsky and P. A. Reynolds

Synopsis: Accurate very low temperature synchrotron-radiation data can now be measured within days, making electron-density studies of compounds beyond the first transition series more frequently within reach.

Online June 1999

Acta Cryst. (1999). B55, 375-379 [ doi:10.1107/S0108768198012907 ]

Thermal vibrations in potassium 3-benzoyl-2-thiophenecarboxylate

B. M. Craven and F. L. Ballas

Synopsis: Thermal vibration analysis indicates that an experimentally determined distance between atomic centroids can be significantly different from the mean interatomic distance that is of chemical interest. This is especially true for distances involved in weak interactions.

Online June 1999

Acta Cryst. (1999). B55, 380-388 [ doi:10.1107/S0108768198012968 ]

Four-component intergrowth structures of the metal-ion cage complexes fac-(1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane)M^II diperchlorate hydrate, [M(C₂₂H₄₈N₆)](ClO₄)₂.xH₂O, M = Ni, Zn

K. J. Haller, A. D. Rae, A. M. T. Bygott, D. C. R. Hockless, S. F. Ralph, R. J. Geue and A. M. Sargeson

Synopsis: These isomorphic crystal structures are described as intergrowths of four substructures, each a different modulation of an idealized parent structure of space group C2/c. Two substructures correspond to alternative orientations of a C1 structure for which x = 0, and two substructures correspond to alternative origins of a P2₁/n structure for which x = 1. The MN₆ coordination geometry is essentially octahedral, in contrast to the trigonal-prismatic geometry observed for the Cd^II and Hg^II complexes of the same ligand.

Online June 1999

Acta Cryst. (1999). B55, 389-395 [ doi:10.1107/S0108768198014281 ]

Crystal structures of [18]aneN₆H₂K[Co(CN)₆].4H₂O, [16]aneN₄H₂K[Co(CN)₆] and [12]aneN₄H₃[Co(CN)₆].2H₂O. Insight into the electrostatic and hydrogen-bonding interaction in self-assembling supercomplexes

P. Zhou, F. Xue, S. C. F. Au-Yeung and X. Xu

Synopsis: The crystal structures of the three supercomplexes [18]aneN₆H₂K[Co(CN)₆].4H₂O, [16]aneN₄H₂K[Co(CN)₆] and [12]aneN₄H₃[Co(CN)₆].2H₂O, and the second-sphere interactions in the binding of the [Co(CN)₆]^3- complex ions with the protonated polyammonium macrocycles are reported.

Online June 1999

Acta Cryst. (1999). B55, 396-409 [ doi:10.1107/S010876819801550X ]

Polynuclear chloromercurate(II) systems in their chloropyridinium salts

A. Linden, B. D. James, J. Liesegang and N. Gonis

Synopsis: The chloromercurate(II) salts of monochloropyridines display a variety of anion stoichiometries and structures. The 2-chloropyridinium salt has the anion stoichiometry [HgCl₃]^-, but the anions are infinite chains composed of [HgCl₃]^-, HgCl₂ and Cl^- moieties linked by longer HgCl contacts. Chains of interconnected [HgCl₄]^2- and HgCl₂ entities in the 3- and 4-chloropyridinium salts yield the rare [Hg₃Cl₁₀]^4- stoichiometry. Second forms of the 3- and 4-chloropyridinium salts contain distorted [Hg₂Cl₆]^2- moieties linked into chains and symmetrical discrete [Hg₂Cl₆]^2-anions, respectively.

Online June 1999

Acta Cryst. (1999). B55, 410-423 [ doi:10.1107/S0108768198016140 ]

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions

F. C. Krebs, B. W. Laursen, I. Johannsen, A. Faldt, K. Bechgaard, C. S. Jacobsen, N. Thorup and K. Boubekeur

Synopsis: The planarity of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations in several salts and their structural chemistry are described.

Online June 1999

Acta Cryst. (1999). B55, 424-431 [ doi:10.1107/S0108768198013494 ]

Molecular aggregation in crystalline 1:1 complexes of hydrophobic D- and L-amino acids. I. The L-isoleucine series

B. Dalhus and C. H. Görbitz

Synopsis: The crystal structures of seven complexes of L-isoleucine with various D-amino acids with hydrophobic side chains are reported. Similarities and differences in the molecular packing and in the conformation of the partner molecule are discussed.

Online June 1999

Acta Cryst. (1999). B55, 432-440 [ doi:10.1107/S0108768198013524 ]

Chiral recognition between host and guest: a binaphthyl-18-crown-6 host with D-phenylglycinium methyl ester perchlorate guest. A difficult structure solved with CRUNCH

D. J. Cram, R. A. G. de Graaff, C. B. Knobler, D. S. Lingenfelter, E. F. Maverick and K. N. Trueblood

Synopsis: The crystal structure of a highly discriminating chiral host, in its complex with a chiral cationic guest, shows the influence of C-HO and C-H [pi] interactions on the unanticipated orientation of the guest in the host cavity. These interactions are very similar, but not identical, in the two independent complexes in the asymmetric unit.

Online June 1999

Acta Cryst. (1999). B55, 441-447 [ doi:10.1107/S0108768198014013 ]

3(5),4-Dimethyl- and 3,4,5-trimethylpyrazole at 200 K. X-ray crystallography and quantum-chemical analysis

L. Infantes, C. Foces-Foces and J. Elguero

Synopsis: The crystal and molecular structure of 3(5),4-dimethylpyrazole and 3,4,5-trimethylpyrazole have been determined at 200 K. Ab initio calculations at HF and B3LYP/6-31G** levels have been undertaken in order to estimate the influence of the methyl substituent on the pyrazole.

Online June 1999

Acta Cryst. (1999). B55, 448-458 [ doi:10.1107/S0108768198017200 ]

Phase-transition-induced twinning in the 1:1 adduct of hexamethylenetetramine and azelaic acid

M. Hostettler, H. Birkedal, M. Gardon, G. Chapuis, D. Schwarzenbach and M. Bonin

Synopsis: Phase III of the 1:1 adduct of hexamethylenetetramine and azelaic acid presents phase-transition-generated TLQS twinning, with a superposition of a carboxylic acid and a carboxylate form of azelaic acid. Four possible single-domain states are predicted by group theory; only one type of domain wall is observed and is explained in terms of intermolecular interactions.

Online June 1999


	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 3 (June 1999)

research papers

Crystal lattice and phase transitions in Na4TiP2O9 (NTP) and Na4.5FeP2O8(O,F) (NFP) superionic conductors as a function of high pressures and temperatures

B. Maximov, M. Sirota, S. Werner and H. Schulz

Cation distribution and crystal chemistry of Y3Al5-xGaxO12 (0 x 5) garnet solid solutions

A. Nakatsuka, A. Yoshiasa and T. Yamanaka

Electron density distribution and Madelung potential in -spodumene, LiAl(SiO3)2, from two-wavelength high-resolution X-ray diffraction data

S. Kuntzinger and N. E. Ghermani

Single-crystal neutron diffraction study of -Cs3(HSO4)2[H2-x(SxP1-x)O4] (x 0.5) at 15 K

S. M. Haile and W. T. Klooster

Arrangement of C atoms in the SiC-C solid solution

O. O. Mykhaylyk and M. P. Gadzira

Structures of Bi14WO24 and Bi14MoO24 from neutron powder diffraction data

C. D. Ling, R. L. Withers, J. G. Thompson and S. Schmid

The crystal structure of Ca7Zr7Ta6O36 refined using synchrotron-radiation data

S. Schmid, J. G. Thompson, R. L. Withers, C. D. Ling, N. Ishizawa and S. Kishimoto

Synchrotron X-ray analysis of the electron density in HoFe2

V. A. Streltsov and N. Ishizawa

Determination of the site of incorporation of cobalt in CoZnPO-CZP by multiple-wavelength anomalous-dispersion crystallography

M. Helliwell, J. R. Helliwell, V. Kaucic, N. Zabukovec Logar, L. Barba, E. Busetto and A. Lausi

Structural investigation of the negative-thermal-expansion material ZrW2O8

J. S. O. Evans, W. I. F. David and A. W. Sleight

Disparate atomic displacements in skutterudite-type LaFe3CoSb12, a model for thermoelectric behavior

B. C. Chakoumakos, B. C. Sales, D. Mandrus and V. Keppens

The crystal structure of the B-site ordered complex perovskite Sr(Yb0.5Nb0.5)O3

J. H. Yang, W. K. Choo, J. H. Lee and C. H. Lee

Structure analysis of new homologous compounds Ga2O3(ZnO)m (m = integer) by high-resolution analytical transmission electron microscopy

C. Li, Y. Bando, M. Nakamura, K. Kurashima and N. Kimizuka

Accurate charge densities in days - use of synchrotrons, image plates and very low temperatures

B. B. Iversen, F. K. Larsen, A. A. Pinkerton, A. Martin, A. Darovsky and P. A. Reynolds

Thermal vibrations in potassium 3-benzoyl-2-thiophenecarboxylate

B. M. Craven and F. L. Ballas

Four-component intergrowth structures of the metal-ion cage complexes fac-(1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane)MII diperchlorate hydrate, [M(C22H48N6)](ClO4)2.xH2O, M = Ni, Zn

K. J. Haller, A. D. Rae, A. M. T. Bygott, D. C. R. Hockless, S. F. Ralph, R. J. Geue and A. M. Sargeson

Crystal structures of [18]aneN6H2K[Co(CN)6].4H2O, [16]aneN4H2K[Co(CN)6] and [12]aneN4H3[Co(CN)6].2H2O. Insight into the electrostatic and hydrogen-bonding interaction in self-assembling supercomplexes

P. Zhou, F. Xue, S. C. F. Au-Yeung and X. Xu

Polynuclear chloromercurate(II) systems in their chloropyridinium salts

A. Linden, B. D. James, J. Liesegang and N. Gonis

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions

F. C. Krebs, B. W. Laursen, I. Johannsen, A. Faldt, K. Bechgaard, C. S. Jacobsen, N. Thorup and K. Boubekeur

Molecular aggregation in crystalline 1:1 complexes of hydrophobic D- and L-amino acids. I. The L-isoleucine series

B. Dalhus and C. H. Görbitz

Chiral recognition between host and guest: a binaphthyl-18-crown-6 host with D-phenylglycinium methyl ester perchlorate guest. A difficult structure solved with CRUNCH

D. J. Cram, R. A. G. de Graaff, C. B. Knobler, D. S. Lingenfelter, E. F. Maverick and K. N. Trueblood

3(5),4-Dimethyl- and 3,4,5-trimethylpyrazole at 200 K. X-ray crystallography and quantum-chemical analysis

L. Infantes, C. Foces-Foces and J. Elguero

Phase-transition-induced twinning in the 1:1 adduct of hexamethylenetetramine and azelaic acid

M. Hostettler, H. Birkedal, M. Gardon, G. Chapuis, D. Schwarzenbach and M. Bonin

related papers

Crystal lattice and phase transitions in Na₄TiP₂O₉ (NTP) and Na_4.5FeP₂O₈(O,F) (NFP) superionic conductors as a function of high pressures and temperatures

Cation distribution and crystal chemistry of Y₃Al_5-xGa_xO₁₂ (0 x 5) garnet solid solutions

Electron density distribution and Madelung potential in -spodumene, LiAl(SiO₃)₂, from two-wavelength high-resolution X-ray diffraction data

Single-crystal neutron diffraction study of -Cs₃(HSO₄)₂[H_2-x(S_xP_1-x)O₄] (x 0.5) at 15 K

Structures of Bi₁₄WO₂₄ and Bi₁₄MoO₂₄ from neutron powder diffraction data

The crystal structure of Ca₇Zr₇Ta₆O₃₆ refined using synchrotron-radiation data

Synchrotron X-ray analysis of the electron density in HoFe₂

Structural investigation of the negative-thermal-expansion material ZrW₂O₈

Disparate atomic displacements in skutterudite-type LaFe₃CoSb₁₂, a model for thermoelectric behavior

The crystal structure of the B-site ordered complex perovskite Sr(Yb_0.5Nb_0.5)O₃

Structure analysis of new homologous compounds Ga₂O₃(ZnO)_m (m = integer) by high-resolution analytical transmission electron microscopy

Four-component intergrowth structures of the metal-ion cage complexes fac-(1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane)M^II diperchlorate hydrate, [M(C₂₂H₄₈N₆)](ClO₄)₂.xH₂O, M = Ni, Zn

Crystal structures of [18]aneN₆H₂K[Co(CN)₆].4H₂O, [16]aneN₄H₂K[Co(CN)₆] and [12]aneN₄H₃[Co(CN)₆].2H₂O. Insight into the electrostatic and hydrogen-bonding interaction in self-assembling supercomplexes