Crystal structure of pollucite

Abstract

AbstractThe crystal structure of pollucite (ANA) (Cs,Na)AlSi2O6is characterized by single-crystal X-ray diffractometry. The space groupC2/c,monoclinic, is found to be the most probable space group for this mineral based on the systematic absences of reflections. Cesium ions or water molecules are disordered at the center of a channel and are slightly apart from the special position. This is the origin of symmetry breaking and the space group becomes lower fromIa-3d(analcime) toC2/c. Sodium ions or vacancies are located at the contact point of the channel. No ordering of aluminum is observed in the pollucite structure.