Structural Science

 

Acta Cryst. (2004). B60, 1-9  [ doi:10.1107/S0108768103026582 ]

Local and long-range order in ferroelastic lead phosphate at high pressure

R. J. Angel, U. Bismayer and W. G. Marshall

Synopsis: Neutron and X-ray diffraction studies indicate that at high pressure the monoclinic to trigonal phase transition in lead phosphate is accompanied by the development of static disorder of the Pb atoms. This disorder in the trigonal phase is suppressed at pressures more than 1  GPa above the transition pressure at room temperature.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 10-20  [ doi:10.1107/S0108768103026661 ]

Jahn-Teller distortions, cation ordering and octahedral tilting in perovskites

M. W. Lufaso and P. M. Woodward

Synopsis: Cooperative Jahn-Teller distortions and their interplay with octahedral tilting and cation ordering have been examined systematically in AMX₃ perovskites containing a Jahn-Teller ion on the octahedral site, as well as in quaternary A₂MM'X₆ perovskites containing a Jahn-Teller ion on one-half of the octahedral sites.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 21-31  [ doi:10.1107/S010876810302901X ]

Superspace description of NaCa₄Nb₅O₁₇ (a perovskite-related compound of the type A_nB_nO_3n+2) as a modulated layered structure

L. Elcoro, F. J. Zúñiga and J. M. Perez-Mato

Synopsis: An alternative superspace description of the perovskite-related compound NaCa₄Nb₅O₁₇ as a commensurate modulated structure with discontinuous atomic domains is proposed. This approach highlights the layered character of the structure and can be applied to predict the space group and structure of other members of the [Na,Ca]_nNb_nO_3n+2 compound series.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 32-40  [ doi:10.1107/S0108768103025138 ]

Structures and phase transitions of trigonal ZrMo₂O₈ and HfMo₂O₈

S. Allen, R. J. Ward, M. R. Hampson, R. K. B. Gover and J. S. O. Evans

Synopsis: This paper describes the structures and thermal expansion properties of trigonal ZrMo₂O₈ and HfMo₂O₈. Both materials have been shown to undergo displacive phase transitions at high temperature to a new trigonal structure with space group Pm1.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 41-45  [ doi:10.1107/S0108768103027897 ]

An X-ray powder diffraction study of the spin-crossover transition and structure of bis(2,6-dipyrazol-1-ylpyrazine)iron(II) perchlorate

V. A. Money, I. Radosavljevic Evans, J. Elhaïk, M. A. Halcrow and J. A. K. Howard

Synopsis: The crystal structure of an iron(II) spin-crossover compound, [Fe(C₁₀H₈N₆)₂](ClO₄)₂, is solved from X-ray powder diffraction data and the thermal spin transition is monitored using the change in unit-cell parameters with temperature.

Online 21 January 2004

    

Acta Cryst. (2004). B60, 46-64  [ doi:10.1107/S0108768103029136 ]

Hydrated metal(II) complexes of N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl) derivatives of glycine, glycylglycine, threonine, serine, valine and methionine: a monomeric complex and coordination polymers in one, two and three dimensions linked by hydrogen bonding

M. L. Godino Salido, P. Arranz Mascarós, R. López Garzón, M. D. Gutiérrez Valero, J. N. Low, J. F. Gallagher and C. Glidewell

Synopsis: The title ligands form hydrated complexes with Ca²⁺, Sr²⁺ and Ba²⁺ in which the metal-ligand coordination may give finite (zero-dimensional) entities or coordination polymers on one, two or three dimensions.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 65-75  [ doi:10.1107/S0108768103026739 ]

Adducts of 1,4,8,11-tetraazacyclotetradecane with carboxylic acids: hydrogen-bonded supramolecular structures in two or three dimensions

C. M. Zakaria, A. J. Lough, G. Ferguson and C. Glidewell

Synopsis: With a variety of carboxylic acids, 1,4,8,11-tetraazacyclotetradecane forms solvated salts that contain hydrogen-bonded supramolecular structures in two or three dimensions.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 76-89  [ doi:10.1107/S0108768103024856 ]

Symmetrically 4,6-disubstituted 2-aminopyrimidines and 2-amino-5-nitrosopyrimidines: interplay of molecular, molecular-electronic and supramolecular structures

A. Quesada, A. Marchal, M. Melguizo, J. N. Low and C. Glidewell

Synopsis: In symmetrically 4,6-disubstituted 2-aminopyrimidines, hard hydrogen bonds can generate supramolecular structures in zero, one, two or three dimensions.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 90-96  [ doi:10.1107/S0108768103029173 ]

Supramolecular assembling using synthons with NH-CO(S)-CS-NH and NH-CO-CO-NH functionalities: crystal structures of (S,S)-N,N'-monothiooxalyldileucine methyl ester and its dithio analogue

B. Kojic-Prodic, B. Peric, Z. Stefanic, A. Meden, J. Makarevic, M. Jokic and M. Zinic

Synopsis: A comparison of the structures of (S,S)-dileucine methyl esters with oxalamide, monothiooxalamide and dithiooxalamide bridges is presented. Asymmetric substitution of one oxygen by sulfur leads to packing of the helical hydrogen-bonded supramolecular assemblies with non-crystallographic, approximate 4₁ symmetry along b in the non-polar space group P2₁2₁2₁. Molecules with chemically symmetrical bridges (oxalamide and dithiooxalamide) are packed in the polar space group P4₁ with similar hydrogen-bonded supramolecular assemblies.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 97-102  [ doi:10.1107/S0108768103026284 ]

Different packing in three polymorphs of 2,4,6-trimethoxy-1,3,5-triazine

N. Fridman, M. Kapon, Y. Sheynin and M. Kaftory

Synopsis: 2,4,6-Trimethoxy-1,3,5-triazine is found to exhibit three different polymorphs. The major difference between these polymorphs is the mode of packing of the molecules in the crystal.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 103-107  [ doi:10.1107/S010876810302826X ]

Geometry at the aliphatic tertiary carbon atom: computational and experimental test of the Walsh rule

S. Böhm and O. Exner

Synopsis: Bond lengths and angles in two series of compounds with a tertiary C atom, calculated at the DFT level, conform qualitatively to the Walsh rule. In the presence of an electron-attracting substituent the angles are usually widened and bonds shortened.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 108-120  [ doi:10.1107/S0108768103027605 ]

Quininium (R)-mandelate, a structure with large Z' described as an incommensurately modulated structure in (3+1)-dimensional superspace

A. Schönleber and G. Chapuis

Synopsis: A single-crystal X-ray structure analysis is presented for the incommensurate structure of quininium (R)-mandelate. The structure was solved in two superstructure approximations, with Z'  =  15 and Z'  =  18, and then refined in (3+1)-dimensional space using the superspace approach.

Online 21 January 2004

 

Acta Cryst. (2004). B60, 121-126  [ doi:10.1107/S0108768103028891 ]

Notes for authors 2004

Online 21 January 2004