Atomic Kinetics and Dynamical Phason Disorder in a Quasicrystal

Abstract

ABSTRACTSlow relaxation dynamics in strongly coupled systems is known to be universally described by the stretched exponential Kohlrausch law. However, this phenomenon, observed in various condensed systems, still eludes a comprehensive microscopic interpretation. I discuss here the relaxation dynamics in an equilibrium dodecagonal quasicrystal which demonstrates a pronounced stretched exponential behaviour. The quasicrystal, simulated by Molecular Dynamics, reveals the presence of dynamical phason disorder, a generic form of relaxation dynamics associated with incommensurate, or phason degrees of freedom. This dynamics brings about a novel form of atomic diffusion, which is examined here by calculating the self part of intermediate scattering function Fs(Q, t). The latter displays a non-exponential decay which is found to be described by the Kohlrausch law with the stretching exponent β = 0.47. I discuss here a possible similarity between the dynamics of quasicrystals observed and that of supercooled liquids and glasses.