The structure of some simple amorphous network solids revisited

Wright, Adrian C.; Hulme, Robert A.; Grimley, David I.; Sinclair, Roger N.; Martin, Steve W.; Price, David L.; Galeener, F. L.

doi:10.1016/0022-3093(91)90098-q

Cited by 108 publications

(39 citation statements)

References 30 publications

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“…58 At all temperatures and for all phases, almost every Si atom is fourfold coordinated and almost every O atom is twofold coordinated, in agreement with experimental data. 43,44 Above T m during heating and above T g during cooling, the mean-square displacement of atoms grows linearly with the number of MC steps, showing that the motion of atoms is unbound, consistently with liquidlike diffusion. Comparison of atomic mobilities computed by MC during cooling to experimental data for the diffusion coefficient in disordered silica phases allows us to establish a rough correspondence with a real time scale.…”

Section: Summary Of Results For Bulk Siomentioning

confidence: 95%

“…At ambient temperature, they agree at least qualitatively and, to a large extent, semiquantitatively with experimental data provided by x-ray and neutron diffractions. 43,44 …”

Section: Summary Of Results For Bulk Siomentioning

confidence: 99%

“…36,41 The radial distribution functions and angle probability distributions 42 obtained by this method for low-temperature amorphous samples are in good agreement with experimental data. 43,44 Until recently, models of this type have been used within a static framework or in approaches combining bond switches with energy quenches. 45,46 We applied a similar force field approach supplemented by bond interchanges within an equilibrium scheme to investigate thermal properties of bulk silica.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

Cabriolu

Ballone

2010

Phys. Rev. B

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Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model Cabriolu, R., & Ballone, P. (2010). Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model. Physical Review B (Condensed Matter), 81 (15) A force field model of the Keating type supplemented by rules to break, form, and interchange bonds is applied to investigate thermodynamic and structural properties of the amorphous SiO 2 surface. A simulated quench from the liquid phase has been carried out for a silica sample made of 3888 silicon and 7776 oxygen atoms arranged on a slab ϳ40 Å thick, periodically repeated along two directions. The quench results into an amorphous sample, exposing two parallel square surfaces of ϳ42 nm 2 area each. Thermal averages computed during the quench allow us to determine the surface thermodynamic properties as a function of temperature. The surface tension turns out to be ␥ = 310Ϯ 20 erg/ cm 2 at room temperature and ␥ = 270Ϯ 30 at T = 2000 K, in fair agreement with available experimental estimates. The entropy contribution Ts s to the surface tension is relatively low at all temperatures, representing at most ϳ20% of the surface energy. Almost without exceptions, Si atoms are fourfold coordinated and oxygen atoms are twofold coordinated. Twofold and threefold rings appear only at low concentration and are preferentially found in proximity of the surface. Above the glass temperature T g = 1660Ϯ 50 K, the mobility of surface atoms is, as expected, slightly higher than that of bulk atoms. The computation of the height-height correlation function shows that the silica surface is rough in the equilibrium and undercooled liquid phase, becoming smooth below the glass temperature T g .

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Section: Summary Of Results For Bulk Siomentioning

confidence: 95%

“…At ambient temperature, they agree at least qualitatively and, to a large extent, semiquantitatively with experimental data provided by x-ray and neutron diffractions. 43,44 …”

Section: Summary Of Results For Bulk Siomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

Cabriolu

Ballone

2010

Phys. Rev. B

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“…is found to be appreciable only in the small-k region, up to and including the main peak at kr I .~ (5/2)~r [6]. This remains true when the (narrow) Gaussians are replaced by ~-functions (which only eliminates a small damping, whose effect is negligible in the k-range of interest), and applies afortiori when S(k)s are compared, rather than F(k)s. Thus, in the case of vitreous SiO 2, the shape of the interference function beyond the main peak is rather well reproduced by a sum of two sines, n 1 sin kr 1 + n 2 sin kr2, with r2/r I = 2V~-/3.…”

Section: Structure Factor and Topological Short Range Ordermentioning

confidence: 79%

On the origin of second-peak splitting in the static structure factor of metallic glasses

Waal

1995

Journal of Non-Crystalline Solids

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It is proposed that the splitting of the second peak of the total static structure factor, S(k), of many metallic glasses is essentially the same feature as the indentation at ko-= (9/2)~r in the function (sin ko-+ cr 1 sin kacr), caused by the coincidence of the fourth minimum of the second term with the third maximum of the first term when a = 5/3. Together with the strong-weak relation of the split peak components of S(k), this feature indicates the splitting to be direct evidence for face-sharing of regular tetrahedra (a = 2~/2-/3 ) dominating the topological short range order; increasing the number of face-sharing tetrahedra in local structural units indeed increases the amount of peak splitting in S(k); a dense random packing of well defined identical structural units (DRPSU), with neighbouring units linked together by a shared icosahedron, is described in detail. The packing fraction in a homogeneous, isotropic 1078-atom model is 0.67, after static relaxation under a two-body Lennard-Jones potential.

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“…9). This choice is supported by the fact that the experimental results in neutron scattering factor of silica can be better fitted with a Lorentzian function than with a Gaussian one 63 . It should be noted that the fit has been done on the low Q part of the FSDP to avoid the contribution of the following peaks.…”

Section: First Sharp Diffraction Peakmentioning

confidence: 99%

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

Bauchy

2012

The Journal of Chemical Physics

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Structural, vibrational and thermal properties of densified sodium silicate (NS2) are investigated with classical molecular dynamics simulations of the glass and the liquid state. A systematic investigation of the glass structure with respect to density was performed. We observe a repolymerization of the network manifested by a transition from a tetrahedral to an octahedral silicon environment, the decrease of the amount of non-bridging oxygen atoms and the appearance of three-fold coordinated oxygen atoms (triclusters). Anomalous changes in the medium range order are observed, the first sharp diffraction peak showing a minimum of its full-width at half maximum according to density. The previously reported vibrational trends in densified glasses are observed, such as the shift of the Boson peak intensity to higher frequencies and the decrease of its intensity. Finally, we show that the thermal behavior of the liquid can be reproduced by the Birch-Murnaghan equation of states, thus allowing us to compute the isothermal compressibility.

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The structure of some simple amorphous network solids revisited

Cited by 108 publications

References 30 publications

Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

On the origin of second-peak splitting in the static structure factor of metallic glasses

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

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