Orthorhombic low-temperature modifications of compounds Cs3LnCl6 (Ln = Nd-Yb)-preparation and thermodynamic stability

Article abstract of DOI:10.1016/s0040-6031(97)00089-0

The compounds Cs₃LnCl₆ (Ln=Nd-Yb) can be obtained from aqueous solutions with an orthorhombic structure /S.G. Pbcm/, whereas from solutions in anhydrous acetic acid a modification with the monoclinic Cs₃BiCl₆ structure /S.G. C 2/c/ is formed. By solution calorimetry, the orthorhombic phase could be proved to be the low temperature modification. Molar volumes determined from X-ray powder patterns increase from Pbcm to C 2/c. The transition from the orthorhombic into the monoclinic phase is irreversible for kinetical reasons.