We report a molecular dynamics simulation of a simple monatomic glass-forming liquid. It is shown that transition to deeper minima in the energy landscape under supercooling results in the formation of icosahedrally structured domains with distinctly slow diffusion which grow with cooling in a low-dimensional manner and percolate around T(c), the critical temperature of the mode-coupling theory. Simultaneously, a sharp slowing down of the structural relaxation relative to diffusion is observed. It is concluded that this effect cannot be accounted for by the spatial variation in atomic mobility. The low-dimensional clustering is discussed as a possible mechanism of fragility.

This work is devoted to the decay of random solutions of the unforced Burgers equation in one dimension in the limit of vanishing viscosity. The initial velocity is homogeneous and Gaussian with a spectrum proportional to k n at small wavenumbers k and falling off quickly at large wavenumbers.In physical space, at sufficiently large distances, there is an "outer region", where the velocity correlation function preserves exactly its initial form (a power law) when n is not an even integer.When 1 < n < 2 the spectrum, at long times, has three scaling regions : first, a |k| n region at very small ks with a time-independent constant, stemming from this outer region, in which the initial conditions are essentially frozen; second, a k 2 region at intermediate wavenumbers, related to a self-similarly evolving "inner region" in physical space and, finally, the usual k −2 region, associated to the shocks. The switching from the |k| n to the k 2 region occurs around a wavenumber k s (t) ∝ t −1/[2(2−n)] , while the switching from k 2 to k −2 occurs around k L (t) ∝ t −1/2 (ignoring logarithmic corrections in both instances).When −1 < n < 1 there is no inner region and the long-time evolution of the spectrum is self-similar.When n = 2, 4, 6, . . . the outer region disappears altogether and the long-time evolution is again self-similar. For other values of n > 2, the outer region gives only subdominant contributions to the small-k spectrum and the leading-order long-time evolution is also self-similar.The key element in the derivation of the results is an extension of the Kida (1979) log-corrected 1/t law for the energy decay when n = 2 to the case of arbitrary integer or non-integer n > 1. A systematic derivation is given in which both the leading term and estimates of higher order corrections can be obtained. It makes use of the BalianSchaeffer (1989) formula for the distribution in space of correlated particles, which gives the probability of having a given domain free of particles in terms of a cumulant expansion. The particles are, here, the intersections of the initial velocity potential with suitable parabolas. The leading term is the Poisson approximation used in previous work, which ignores correlations.High-resolution numerical simulations are presented which support our findings.2

Using an analytical theory, experimental terahertz time-domain spectroscopy data, and numerical evidence, we demonstrate that the frequency dependence of the absorption coupling coefficient between far-infrared photons and atomic vibrations in disordered materials has the universal functional form, C(omega)=A+Bomega(2), where the material-specific constants A and B are related to the distributions of fluctuating charges obeying global and local charge neutrality, respectively.

The global minima of clusters bound by a Dzugutov potential form non-compact polytetrahedral clusters mainly composed of interpenetrating and face-sharing 13-atom icosahedra. As the size increases, these icosahedral units first form linear arrays, then two-dimensional rings, then threedimensional networks. Characterization of the energy landscapes of these clusters shows that they are particularly rough and generally exhibit a multiple-funnel topography. These results provide new insights into the structure and dynamics of bulk supercooled Dzugutov liquids and the form of the bulk phase diagram.

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