ELASTIC ISOTROPY AND ANISOTROPY IN QUASI-CRYSTALLINE AND CUBIC ALCULI

Unlike conventional crystals, quasicrystals are predicted to be elasti cally isotropic. To confirm this prediction experimentally, one must d istinguish the quasicrystal from nearly isotropic crystals, which requ ires a high degree of precision. We report the use of resonant ultraso und spectroscopy to determine that the AlCuLi quasicrystal is isotropi c within 0.07%, significantly more isotropic than any conventional cry stal (by 10 standard deviations). By contrast, we find that a closely related cubic phase of AlCuLi is slightly, but measurably, anisotropic .