Some questions on charge ordering in th3P4-type mixed-valence rare-earth compounds
Abstract
The first description of a Th3P4-type rare-earth chalcogenide was published by Zachariasen (1948, 1949). This work on the Ce2S3-Ce3S4 system established the point of view that the 3: 4 composition had both the metal sites filled (12 (a) positions, International Tables for X-ray Crystallography, space group 143d) and all the sulphur sites filled (16c) with four formula units per unit cell. Based on powder diffraction data, Zachariasen determined that the Ce2S3 structure also had all sulphur sites filled but that there were vacancies on the 12 metal-ion sites with 10⅔ Ce atoms distributed randomly in the lattice. The single parameter associated with the anion positions was estimated at x = 0.083 ± 0.015. The metal-atom-site population for the 2:3 compound was based on a measured density, ρ = 5.25 ± 0.10 g cm-3, which is slightly higher than his theoretical density, ρ = 5.186 g cm-3. © 1980 Taylor & Francis Ltd.