Low-frequency atomic motion in a model glass

Mazzacurati, V.; Ruocco, G.; Sampoli, M.

doi:10.1209/epl/i1996-00515-8

Cited by 122 publications

(124 citation statements)

References 17 publications

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“…The time scales predicted by the structure factors are in good agreement with those predicted by NMD at low frequencies. Similar agreement has been reported in other models of amorphous materials [6,[76][77][78]. The agreement between the NMD-predicted lifetimes and the structure factor time scales for a-Si at low frequencies indicates (5) and (20) with the DOS sound speed from Table I] that these modes are plane-wave-like and that the wave packets formed by these modes are propagating [4,6].…”

Section: Lifetimessupporting

confidence: 87%

Thermal conductivity accumulation in amorphous silica and amorphous silicon

2014

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We predict the properties of the propagating and nonpropagating vibrational modes in amorphous silica (a-SiO 2 ) and amorphous silicon (a-Si) and, from them, thermal conductivity accumulation functions. The calculations are performed using molecular dynamics simulations, lattice dynamics calculations, and theoretical models. For a-SiO 2 , the propagating modes contribute negligibly to thermal conductivity (6%), in agreement with the thermal conductivity accumulation measured by Regner et al. [Nat. Commun. 4, 1640]. For a-Si, propagating modes with mean-free paths up to 1 μm contribute 40% of the total thermal conductivity. The predicted contribution to thermal conductivity from nonpropagating modes and the total thermal conductivity for a-Si are in agreement with the measurements of Regner et al. The accumulation in the measurements, however, takes place over a narrower band of mean-free paths (100 nm-1 μm) than that predicted (10 nm-1 μm).

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Section: Lifetimessupporting

confidence: 87%

Thermal conductivity accumulation in amorphous silica and amorphous silicon

2014

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“…Recently, it was shown that the spatial distribution of low-frequency quasi-localized normal modes is strongly correlated with the spatial distribution of irreversible reorganization (8). This study and related work (9)(10)(11)(12)(13) underline the importance of understanding the relation between local soft modes and structure in disordered solids. Understanding how features of an inherent structure determine the spatial pattern of motions is of central importance in developing a useful microscopic treatment of glass transitions and is the goal of this article.…”

supporting

confidence: 52%

Rigidity percolation and the spatial heterogeneity of soft modes in disordered materials

Souza

Harrowell

2009

Proc. Natl. Acad. Sci. U.S.A.

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We show how the spatial character of unconstrained motion in a network of bonds can be directly inferred from the topological arrangement of constraints. Relaxation time scales of these soft modes are determined, and from this information we generate spatial maps of the heterogeneous distribution of relaxation times in the disordered network. We show that the nature of the dynamic heterogeneity and its sensitivity to changes in bond configuration depends dramatically on the proximity of the system to the rigidity percolation point.dynamic heterogeneity ͉ glass transition ͉ inherent structure ͉ local mode ͉ supercooled liquid T he kinetic behavior of supercooled liquids is dominated by those configurations, known as inherent structures (1), which correspond to the local minima of the potential energy. This perspective, articulated by Goldstein (2) in 1969, is now generally accepted (3-6). The inherent structures can be regarded as zero-temperature disordered solids. The continuous transition from fluidity to rigidity that characterizes the glass transition is accomplished by the supercooled liquid sampling these disordered solids at nonzero temperatures for durations that increase as the temperature drops. Eventually, a low enough temperature is reached such that 1 local minimum persists indefinitely. To understand the kinetic and structural features of the transitions between different inherent structures we must understand the types of motion available to disordered solids. In this article we start from the proposal that constraint networks provide a general description of such solids and then develop a method for identifying the spatial distribution of the motions that remain unconstrained in such materials (i.e., the soft modes) and the spectrum of relaxation times associated with these modes.In the absence of explicit structural correlates for dynamics, the descriptive approach of dynamic heterogeneities has proved a powerful way forward in developing microscopic accounts of glassy relaxation and in articulating questions about determining dynamics from structure (7). Recently, it was shown that the spatial distribution of low-frequency quasi-localized normal modes is strongly correlated with the spatial distribution of irreversible reorganization (8). This study and related work (9-13) underline the importance of understanding the relation between local soft modes and structure in disordered solids. Understanding how features of an inherent structure determine the spatial pattern of motions is of central importance in developing a useful microscopic treatment of glass transitions and is the goal of this article.Faced with the daunting variety of particle arrangements that typically comprise a disordered solid, geometrical characterizations of such solids are difficult to both perform and interpret. An alternative treatment of amorphous rigidity is based on networks of constraints. The constraint approach to rigidity focuses on topology, instead of geometry, and the global balance between constraints and deg...

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“…In this case one uses a framework (dynamical matrix, etc.) formally similar to the one customarily adopted for harmonic crystals; however, owing to the lack of translational symmetry of the system, it turns out [22] that the eigenstates cannot anymore be represented by plane waves (PW) even at relatively small wavevectors [26]. A scattering experiment, where Q is fixed, is equivalent -via the fluctuation-dissipation relation-to a response experiment, where one study the time evolution of the system after a sinusoidal perturbation (with period 2π/Q) is applied to the system itself.…”

Section: Discussionmentioning

confidence: 99%

Collective dynamics of liquid aluminum probed by inelastic x-ray scattering

Scopigno

Balucani²,

Ruocco

et al. 2000

Phys. Rev. E

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An inelastic X-ray scattering experiment has been performed in liquid aluminum with the purpose of studying the collective excitations at wavevectors below the first sharp diffraction peak. The high instrumental resolution (up to 1.5 meV) allows an accurate investigation of the dynamical processes in this liquid metal on the basis of a generalized hydrodynamics framework. The outcoming results confirm the presence of a viscosity relaxation scenario ruled by a two timescale mechanism, as recently found in liquid lithium.

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Low-frequency atomic motion in a model glass

Cited by 122 publications

References 17 publications

Thermal conductivity accumulation in amorphous silica and amorphous silicon

Thermal conductivity accumulation in amorphous silica and amorphous silicon

Rigidity percolation and the spatial heterogeneity of soft modes in disordered materials

Collective dynamics of liquid aluminum probed by inelastic x-ray scattering

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