Structure of molten trivalent metal bromides studied by using neutron diffraction: the systems DyBr<sub>3</sub>, YBr<sub>3</sub>, HoBr<sub>3</sub> and ErBr<sub>3</sub>
Jonathan C Wasse; Philip S Salmon; Robert G Delaplane
Журнал:
Journal of Physics: Condensed Matter
Дата:
2000-11-20
Аннотация:
The structure of the salts MBr<sub>3</sub>, where M<sup>3+</sup> denotes Dy<sup>3+</sup>, Y<sup>3+</sup>, Ho<sup>3+</sup> or Er<sup>3+</sup>, was investigated by using neutron diffraction. On heating DyBr<sub>3</sub>, YBr<sub>3</sub> and HoBr<sub>3</sub>, a phase transition from the FeCl<sub>3</sub>-type crystal structure to possibly the YCl<sub>3</sub>-type crystal structure was observed. The liquids were studied at the total-structure-factor level and difference function methods were also applied to DyBr<sub>3</sub> and YBr<sub>3</sub> by assuming isomorphous structures. The melts are found to comprise distorted MBr<sub>6</sub><sup>3-</sup> octahedra with M-Br distances comparable to the sum of the ionic radii and there is evidence for a substantial number of edge-sharing configurations. The octahedra pack to give intermediate-range ionic ordering as manifested by the appearance of a first sharp diffraction peak at 0.79(2)-0.87(2) Å<sup>-1</sup> which is associated with cation correlations
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