Reinvestigation of the structure of BaCuSi2O6 – evidence for a phase transition at high temperature

Abstract

Superstructure reflections have been observed in the room-temperature X-ray diffraction pattern of BaCuSi2O6, barium copper disilicate. The tetragonal structure has a fourfold unit-cell volume compared with the original structure determined by Finger et al. [(1989), Am. Mineral. 74, 952–955]. At T s = 610 K BaCuSi2O6 undergoes a structural phase transition upon which the superstructure reflections disappear. The description of the structure in the larger cell removes the crystal-chemical inconsistencies observed for the original structure.