Inflation symmetry is one of the peculiar features of the diffraction pattern of a quasicrystal. However, it is not an exclusive property of quasicrystalline structures and it may be present in incommensurately modulated structures, as shown recently in the Al-Mg system (Donnadieu P et al 1996 J. Physique I 6 1153-64). The conditions that a single modulation parameter of an incommensurate structure must fulfil in order to have inflation symmetry are determined. Although the number of possible distinct inflation-symmetric quasilattices is infinite, from physical/experimental arguments it can be concluded that, in practice, only a few of them can be experimentally observed, the reported phase of the Al-Mg system being one of these particular cases. A quantitative criterion to classify the modulation parameters that give rise to quasilattices with observable inflation symmetry is proposed. The generalization of the analysis of incommensurate structures with more than one single modulation parameter is also discussed. Finally, the inflation parameters of diffraction patterns with rotational point groups of finite order, C N , are compared with the parameters of the one-dimensional case.

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We applied scanning tunneling microscopy (STM) as well as low-energy electron diffraction (LEED) to analyze the initial process of graphitization at [Formula: see text] surfaces. After annealing a [Formula: see text] surface at 1200°C, there appeared many domains with a single graphite layer in the STM image. Each graphite domain was azimuthally disordered to each other. Many large and small domains with various periodicities were observed in the STM image taken after annealing the surface at temperatures higher than 1300°C. These STM images can be explained as Moiré patterns due to different combinations of two graphite layers. In a LEED pattern azimuthally rotated graphite 1 × 1 spots are observed together with the fundamental 6H-SiC(0001)(1 × 1) spots, in consistent with the STM result.

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