Average and super structure ofβeucryptite (LiAlSiO4) Part II. Superstructure

The superstructure of β eucryptite shows an alternating sequence of Si and Al layers. For a Si-Al ratio of 1:1 only in this arrangement each AlO 4 or SiO 4 tetrahedron can be surrounded by four SiO 4 or AlO 4 tetrahedra, respectively. The Li atoms also have an ordered distribution. The following mean values of bond distances were obtained: Si–O = 1.606 Å, Al–O = 1.733 Å, Li–O = 2.02 Å. The shortest O–O distance of SiO 4 tetrahedra is 2.48 Å. For refinements with anisotropic temperature factors the final R values of the superstructure reflections and of all reflections were 0.088 and 0.057, respectively.