The crystal structure of Rb5B19O3, monoclinic, sp. gr. C2lc, a = 18.211(3), b = 11.519(2), c = 13.310(2) Å, β= 95.63(1)°, V = 2778(1) Å3, Z = 4, dcalc = 2.714 g/cm3. It is determined by X-ray diffraction analysis (P21 Syntex diffractometer, MoKα radiation, 2280 reflections, R = 0.050) starting from the atomic coordinates for the isotructural K5B19O31. The thermal vibrations of Rb and O atoms are considered in the anisotropic approximation. The structure is a three-dimensional framework built of complicated anions of four types: triangles; tetrahedra; [BIVBIII 2O5]- ringsconsisting of two triangles and a tetrahedron; and double [BIVBIII 4O8]- rings consisting of two simple rings with sharing a tetrahedron. Alternating ordinary and double rings form helical chains about the 21 screw axes. Contraction of these chains during heating is presumably the main reason for a strong anisotropy of thermal strain revealed in the crystals by high-temperature X-ray diffraction method.
|Number of pages||6|
|State||Published - 1 Mar 1999|
Scopus subject areas
- Condensed Matter Physics