The synthesis and structures of complex rare-earth halides

The history and contemporary theories of the polarisation of molecules and crystals are considered and a systematic survey is given of dipole moments and bond ionicities in molecular chemical compounds and also of the effective charges of atoms in crystals. An interpretation of these results is given from the standpoint of the electronegativity concept. Views concerning the effective valencies and coordination numbers of atoms in crystals are considered. Bibliography of 207 references.

https://iopscience.iop.org/article/10.1070/RC1982v051n07ABEH002900/pdf

Dielectric Methods of Studying the Chemical Bond and the Concept of Electronegativity

Properties of lead difluoride are considered. Phase equilibria in PbF2–MFn systems (n = 1–5) and data on compounds and solid solutions formed in these systems are analysed. The characteristic features of phase diagrams of systems involving lead difluoride are discussed. Composites of PbF2 with other inorganic compounds hold promise as a basis for the design of new functional materials. The bibliography includes 331 references.

Lead difluoride and related systems

A Fourier analysis of X-ray scattering by glasses in the system ZrF4-BaF2 is presented. The first peak in the radial distribution functions occurs in the range 0.209 to 0.211 nm; the average coordination numbers estimated for the zirconium atom are in the range 7.08 to 8.35, depending on the chemical composition. The second peak has been broken down into two components attributed to two kinds of Ba-F distances, 0.261 to 0.266 and 0.307 to 0.319 nm, with a corresponding coordination number of barium with respect to fluorine atoms ranging from 8.70 to 10.68. Interpretation of the cation-cation region is suggested; the average angle values of the Zr-F-Zr bridge bond, varying from 150° to 160° prevent two neighboring zirconium atoms from being bonded through two fluorine atoms. Comparative discussions with crystalline structures of fluorozirconates are presented.

X‐Ray Scattering Studies of Glasses in the System ZrF4‐BaF2

Chapter 45 Rare earth fluorides

Neu dargestellt wurden BaZrF6, PbZrF6, EuZrF6 und SrZrF6 (alle farblos); diese kristallisieren nach Einkristalldaten orthorhombisch D–Cmma; BaZrF6: a = 7,681, b = 11,357, c = 5,511 A; PbZrF6: a = 7,546, b = 11,118, c = 5,308 A; EuZrF6: a = 7,553, b = 10,945, c = 5,339 A; SrZrF6: a = 7,547, b = 10,889, c = 5,326 A.



Die Strukturbestimmung an BaZrF6 zeigt, das, ahnlich dem K2ZrF6 [3], [ZrF4/2F4/1]-Einer-einfachketten vorliegen, Zr4+ also von 8 F− umgeben ist (Abstande sowie Parameter vgl. Text).



Der Madelung-Anteil der Gitterenergie, MAPLE, sowie „Effektive Koordinationszahlen”, ECoN, werden berechnet und diskutiert.



New Hexafluorozirconates(IV): BaZrF6, PbZrF6, EuZrF6, SrZrF6



The new compounds BaZrF6, PbZrF6, EuZrF6 und SrZrF6 (all colourless) crystallize according to single crystal investigations orthorhombic. Data see „Inhaltsubersicht”.



From the determination of crystal structure of BaZrF6 results, that similar to K2ZrF6, there are [ZrF4/2F4/1]-chains. Zr4+ is therefore surrounded by eight fluorine atoms (distances and parameters see text).



The Madelung part of lattice energy (MAPLE) as well as the effective coordination numbers (ECoN) are calculated and discussed.

B. Mehlhorn

Papers

Neue Hexafluorozirkonate(IV): BaZrF6, PbZrF6, EuZrF6, SrZrF6