VITRIFICATION AND STRUCTURAL DIFFERENCES BETWEEN METAL GLASS, QUASI-CRYSTAL, AND FRANK-KASPER PHASES

The concept of icosahedral short-range order is extended to metallic g lass, quasicrystal, and Frank-Kasper phases. The cluster model, togeth er with the theory of local structural fluctuations, explains the stat ic elasticity of glass, which distinguishes glass from liquid. An elas tic peak of the dynamic structural factor indicates the possibility of transverse mode propagation in glass. As opposed to dislocation and d isclinations in crystals, those in glass are artificially introduced d efects, which serve as easily perceptible structural models. Thermodyn amic relaxation theory may only be used for limited groups of vitrifyi ng compounds; the same applies to representation of vitrification as t he second-order phase transition. The structure of real quasicrystals may not be adequately represented by Penrose tiling, even after it dec oration. This is associated with packing defects, inclusions of other phases, and chemical inhomogeneities. Quasicrystals hav specific defec ts in an icosahedrally coordinated network of bonds, which distinguish them from Frank-Kasper phases. Criteria for isolating physically real izable Penrose tiling from all possible mosaics of this type are sugge sted. Structural distortion that transfer the diffraction rings of qua sicrystalline samples into ellipses are explicable even in a linear ap proximation for the stress field created by a phason. The term ''long- range order'' seems to be wrong even for ordinary crystals. For quasic rystals, the notion of ''rotational'' order is more pertinent.