Mikhail Dzugutov

Decoupling of diffusion from structural relaxation and spatial heterogeneity in a supercooled simple liquid.

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.

The favored cluster structures of model glass formers

We examine the favored cluster structures for two new interatomic potentials, which both behave as monatomic model glass formers in bulk. We find that the oscillations in the potential lead to global minima that are noncompact arrangements of linked 13-atom icosahedra. The structural properties of the clusters correlate with the glass forming propensities of the potentials, and with the fragilities of the corresponding supercooled liquids.

Formation of large-scale icosahedral clusters in a simple liquid approaching the glass transition

A number of singularities observed in super-cooled liquids approaching the glass transition point are commonly interpreted as indicating spatial heterogeneity. This conjecture assumes that the whole volume is decomposed into structurally distinct domains. In simple super-cooled liquids, the assumed domain structure is usually associated with icosahedral clustering; however, no evidence for growing length scale of icosahedral ordering in a super-cooled liquid has been found so far. We present a molecular dynamics simulation demonstrating formation of extended icosahedral configurations in a simple monatomic liquid approaching the glass transition temperature. An important observation is that these configurations show a tendency for low-dimensional growth.

Anomalous slowing down in the metastable liquid of hard spheres.

It is demonstrated that a straightforward extension of the Arrhenius law accurately describes diffusion in the thermodynamically stable liquid of hard spheres. A sharp negative deviation from this behavior is observed as the liquid is compressed beyond its stability limit. This dynamical anomaly can be compared with the nonlinear slowing down characteristic of the supercooled dynamics regime in liquids with continuous interaction. It is suggested that the observed dynamical transition is caused by long-time decomposition of the configuration space. This interpretation is corroborated by the observation of characteristic anomalies in the geometry of a particle trajectory in the metastable domain.

Dynamical diagnostics of ergodicity breaking in supercooled liquids

The phenomenon of liquid-glass transition is commonly associated with ergodicity breaking. It is apparent that the structurally arrested glassy phase is non-ergodic. However, finding unambiguous criteria that would allow one to detect the crossover from ergodic to non-ergodic behaviour in a liquid subjected to supercooling remains a problem of profound conceptual interest. Moreover, meaningful criteria of ergodicity must be expressed in terms of finite-time observation of macroscopically measurable quantities. This paper discusses a new diagnostics of non-ergodicity in supercooled liquids based on comparing the entropy and diffusion.

Medium-range order in a simple monatomic liquid

The origin of intermediate-range structure in a simple monatomic liquid is analysed using the concept of vacancy ordering. The liquid, simulated by molecular dynamics, features an anomalous long-wavelength prepeak in its structure factor, a signature of structural order at intermediate distances. We present convincing evidence that this structural anomaly can be accounted for by the ordering of vacancy-like voids in the structure. It is concluded that the presence of well-defined atom-sized voids, as well as their participation in the medium-range structure may be explained by the predominantly icosahedral local order of this liquid. The results of this study are thus relevant to simple metallic glass-formers which possess a similar type of local order.

Vibrational properties of the one-component σ phase

A structural model of a one-component

Molecular dynamics study of the coherent density correlation function in a supercooled simple one-component liquid

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Evidence for a simple monatomic ideal glass former: The thermodynamic glass transition from a stable liquid phase

-phase crystal has been constructed by means of molecular dynamics simulation. The phonon dispersion curves and the vibrational density of states were computed for this model. The dependence of the vibrational properties on the thermodynamical parameters was investigated. The vibrational density of states of the

Evidence for a liquid-solid critical point in a simple monatomic system

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