Cu:Si(111)(5.55x5.55) 2D Quasicrystal?

Since multiple scattering effects are absent in helium Diffraction, we can verify that the 'quasi-5x5' structure of Cu:Si(111) seen with LEED is actually an incommensurate reconstruction with a unit cell size 5.55 times larger than a (1x1)Si(111) cell. Drawing upon STM photos we postulate the following: The copper introduces a (1x1) structure which is severely strained, containing defects every 5 or 6 lattice spacings to relieve the strain. The whole is strictly tied to the underlying (1x1) lattice, however, amounting to a quasi-random tiling on the discrete (1x1) template to produce 5.55 sup th diffraction spots.