UNDERSTANDING TWELVEFOLD SYMMETRY IN ELECTRON-DIFFRACTION PATTERNS

Electron-diffraction patterns with twelvefold rotational symmetry of experimental alloy phases are assumed to be produced by periodic structures. Several three-dimensional periodic structures are presented based on the so-called T polyhedra. These structures can be used as atomic models to describe the alloy phases. The Fourier-transform patterns of the models are found to be in good agreement with all of the corresponding electron-diffraction patterns of these alloy phases. Details of the motivations and approaches that lead to these models are also discussed.