Dynamics of silica glass: two-level tunnelling states and low-energy floppy modes

Trachenko, Kostya; Dove, Martin T.; Harris, Mark; Heine, Volker

doi:10.1088/0953-8984/12/37/304

Cited by 62 publications

(99 citation statements)

References 50 publications

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“…Empirically a boson peak is observed in all these materials [95]. Numerically, a plateau indeed appears in D(ω) at roughly the same frequency in the cristobalite α and β [68] and in the glass, as shown in Fig. (8.2).…”

Section: The Boson Peak Of Silicamentioning

confidence: 51%

“…Indeed, a tetrahedral network is isostatic, see e.g. [68]. The counting of degrees of freedom can be made as follows: on the one hand each tetrahedron has 6 degrees of freedom (3 rotations and 3 translations).…”

Section: Application To Tetrahedral Networkmentioning

confidence: 99%

“…8.2: Density of states of silica glass (at temperatures of 10 and 300 Kelvins), α-cristobalite and β-cristobalite. This figure is taken from the simulations of [68].…”

Section: The Boson Peak Of Silicamentioning

confidence: 99%

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On the rigidity of amorphous solids

2005

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We poorly understand the properties of amorphous systems at small length scales, where a continuous elastic description breaks down. This is apparent when one considers their vibrational and transport properties, or the way forces propagate in these solids. Little is known about the microscopic cause of their rigidity. Recently it has been observed numerically that an assembly of elastic particles has a critical behavior near the jamming threshold where the pressure vanishes. At the transition such a system does not behave as a continuous medium at any length scales. When this system is compressed, scaling is observed for the elastic moduli, the coordination number, but also for the density of vibrational modes. In the present work we derive theoretically these results, and show that they apply to various systems such as granular matter and silica, but also to colloidal glasses. In particular we show that: (i) these systems present a large excess of vibrational modes at low frequency in comparison with normal solids, called the "boson peak" in the glass literature. The corresponding modes are very different from plane waves, and their frequency is related to the system coordination; (ii) rigidity is a non-local property of the packing geometry, characterized by a length scale which can be large. For elastic particles this length diverges near the jamming transition; (iii) for repulsive systems the shear modulus can be much smaller than the bulk modulus. We compute the corresponding scaling laws near the jamming threshold. Finally, we discuss the implications of these results for the glass transition, the transport, and the geometry of the random close packing.

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Section: The Boson Peak Of Silicamentioning

confidence: 51%

Section: Application To Tetrahedral Networkmentioning

confidence: 99%

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On the rigidity of amorphous solids

2005

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“…This suggests modeling silica as an assembly of stiff tetrahedra connected by flexible joints, the RUM model [123], as sketched in Fig. 1.14.…”

Section: Low-temperature Excitations and The Boson Peak In Covalent Gmentioning

confidence: 99%

The jamming scenario—an introduction and outlook

Liu

Nagel

Saarloos

et al. 2011

Dynamical Heterogeneities in Glasses, Colloids, and Granular Media

119

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Abstract. The jamming scenario of disordered media, formulated about 10 years ago, has in recent years been advanced by analyzing model systems of granular media. This has led to various new concepts that are increasingly being explored in in a variety of systems. This chapter contains an introductory review of these recent developments and provides an outlook on their applicability to different physical systems and on future directions. The first part of the paper is devoted to an overview of the findings for model systems of frictionless spheres, focussing on the excess of low-frequency modes as the jamming point is approached. Particular attention is paid to a discussion of the cross-over frequency and length scales that govern this approach. We then discuss the effects of particle asphericity and static friction, the applicability to bubble models for wet foams in which the friction is dynamic, the dynamical arrest in colloids, and the implications for molecular glasses.

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“…Trachenko et al [144], [145] have been investigating the network rigidity of GeO 2 and SiO 2 under pressure. Rigidity usually appears when the number of mechanical constraints per atom, arising from interatomic interaction (mostly bond stretching and bond bending) becomes greater than the number of degrees of freedom [146].…”

Section: Pressure Induced Rigidity and Intermediate Phasesmentioning

confidence: 99%

The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

228

252

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Abstract. Germanium dioxide (GeO 2 ) is a chemical analogue of SiO 2 . Furthermore, it is also to some extent a structural analogue, as the low and high-pressure short-range order (tetrahedral and octahedral) is the same. However, a number of differences exist. For example, the GeO 2 phase diagram exhibits a smaller number of polymorphs, and all three GeO 2 phases (crystalline, glass, liquid) have an increased sensitivity to pressure, undergoing pressure induced changes at much lower pressures than their equivalent SiO 2 analogues. In addition, differences exist in GeO 2 glass in the medium range order, resulting in the glass transition temperature of germania being much lower than for silica. This review highlights the structure of amorphous GeO 2 by different experimental (e.g., Raman and NMR spectroscopy, neutron and x-ray diffraction) and theoretical methods (e.g., classical molecular dynamics, ab initio calculations). It also addresses the structure of liquid and crystalline GeO 2 that have received much less attention. Furthermore, we compare and contrast the structural differences between GeO 2 and SiO 2 , as well as, along the GeO 2 − SiO 2 join. It is probably a very timely review as interest in this compound, that can be investigated in the liquid state at relatively low temperatures and pressures, continues to increase.

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Dynamics of silica glass: two-level tunnelling states and low-energy floppy modes

Cited by 62 publications

References 50 publications

On the rigidity of amorphous solids

On the rigidity of amorphous solids

The jamming scenario—an introduction and outlook

The structure of amorphous, crystalline and liquid GeO₂

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Dynamics of silica glass: two-level tunnelling states and low-energy floppy modes

Cited by 62 publications

References 50 publications

On the rigidity of amorphous solids

On the rigidity of amorphous solids

The jamming scenario—an introduction and outlook

The structure of amorphous, crystalline and liquid GeO2

Contact Info

Product

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The structure of amorphous, crystalline and liquid GeO₂