A Raman study of RbSnBr3

Abstract

The Raman spectrum of rubidium tribromostannate, RbSnBr3, has been measured as a function of temperature between 14 and 520 K. On cooling the RbSnBr3 crystal, the low-energy portion of the spectrum undergoes marked changes, suggesting the occurrence of a structural phase transition. A low-lying wing feature appears below 170 K, while the lowest-energy lattice band is found to soften from 19.6 cm-1 at 14 K to ca. 15 cm-1 at 140 K. The results are interpreted on the basis of a tin coordination of octahedral bromide ions. The phase transition is probably displacive in character and is associated with a rotation of the SnBr6 octahedra.