Problems in determining the structure of TiBe2 by convergent-beam electron diffraction

Abstract

Abstract The point and space groups of TiBe2 are determined to be m3m and Fd3m with the convergent-beam electron diffraction (CBED) technique. However, it is found that, at certain zone axes, CBED may result in an ambiguity in distinguishing between the point groups m3m and the closely related 3m. The cause of this ambiguity is discussed and attributed to the degree of non-centrosymmetry of the point group 3m when compared with the centrosymmetric point group m3m. Three possible approaches to solving this problem are compared. It is found that the method of deducing the point group from the possible space group possesses the best sensitivity for distinguishing between the point groups m3m and 3m. This approach is used to confirm that the point group of TiBe2 is indeed m3m and therefore its space group is Fd3m.