Valence fluctuations in the incommensurately modulated structure of calaverite AuTe₂

compatible with A1-Fe phases in the same composition range; (3) the m value is ~4.0-4.4; (4) the strongest diffraction spots are fundamental, i.e. most atoms scatter in phase. From these assumptions, a framework of 126 atoms in the unit cell was set up, which produced the strongest diffraction spots. 'Vacancies' and Fe atoms were distributed in the framework by trial and error to obtain the correct 'strong' and 'weak' reflections for the other diffraction spots. The model gave qualitative, but not fully satisfying, agreement with diffraction patterns. The model could explain the experimental HREM images, in the (100} as well as the (110) projection. This suggests that the main features of the model may be correct. On the other hand, the contrast of HREM images depended strongly on crystal thickness, questioning whether a projected structure interpretation of HREM images is applicable, even for the thinnest crystals. [0011 I 60 k