September 1995 issue
Substitution of 2Ti4+ in the structure of KTiOPO4 (KTP) by Ni2+ and W6+ leads to the new non-centrosymmetric compound K2NiWO2(PO4)2 (KNiWP). The structures of KTP and KNiWP are closely related.
The crystal structure of CsNbOB2O5 represents the basic structure type of the borate family AMOB2O5 with A = K, Rb, Cs, Tl and M = Nb, Ta. The structure contains untilted chains of [NbO6] octahedra linked by planar [B2O5] groups. Cs is coordinated irregularly by eight O atoms.
The structure of SrTa4O11 contains layers of TaO7 pentagonal bipyramids sharing edges, as found in U3O8. Between the layers lie Sr atoms with distorted cubic coordination geometry and Ta atoms with distorted octahedral coordination geometry.
The structure of ScSn2 is related to the ZrSi2 structure type and contains slabs of Sc trigonal prisms centred by Sn. Sc6Pb5, isotypic with Ti6Ge5, is characterized by infinite columns of Sc tetragonal antiprisms centred by Pb and by infinite columns of Pb octahedra centred by Sc atoms.
The outstanding features of this new vierer single-chain silicate are the large stretching factor of the silicate chain of fs = 96.8%, a very small Si-O-Si angle of 118.3° and the presence of three-membered rings formed from two [SiO4] and one [ZnO4] tetrahedra.
The cage compound Cl8Si8O12 shows a close structural resemblance to the compound (CH3)8Si8O12. As a result of interelectronic repulsion and the considerable electronegativity of the Cl substituent, distortions of the tetrahedral Si environment and a shortening of the Si-O bond occur.
Analysis of previously published diffraction data shows that Cu(AlCl4)2 is monoclinic. Refinement on this basis gives an improved R factor. The changes in the structure are small.