Figure 1597 shows the projection-diffraction symmetry of the [1-100] CBED pattern of a T1 (Al₂CuLi) crystal. [1] The pattern symmetry from such a crystal in the [1-100] direction is 2mm. However, this diffraction symmetry does not show perfect 2mm symmetry due to slight misalignment of the second condenser aperture. Two typical reasons that cause the alignment difficulties are the broad diffuse intensity of the zero-order Laue zone (ZOLZ) pattern and the very close spacing between reflections.

[1] Kenneth S. Vecchio and David B. Williams, Convergent Beam Electron Diffraction Analysis of the T1 (Al2CuLi) Phase in Al-Li-Cu Alloys, Metallurgical Transactions A, 19A, 1988-2885, (1988).