We report phason defects in the stable Al-Cu-Co-Si decagonal quasicrystal obtained by an Ammann-line analysis of a tiling derived from a high-resolution electron microscope image, covering an area of about 25×34 ${\mathrm{nm}}^2$. Ammann-line jags, corresponding to matching rule violations, are about 4% of the total tiling edges. This supports the quasiperiodic-tiling model of quasicrystals.

• Received 12 April 1994

DOI:https://doi.org/10.1103/PhysRevB.50.3645