Topological constraint model of high lithium content borate glasses

Takeda, Wataru; Wilkinson, Collin J.; Feller, Steve; Mauro, John C.

doi:10.1016/j.nocx.2019.100028

Cited by 5 publications

(4 citation statements)

References 16 publications

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“…[11]. T g is in fact a nonmonotonic function of x in the here explored x range [30]. (ii) The induced dynamics is faster ( E a (Q max ) smaller) for larger x as a consequence of the dynamics of the alkalis being faster, as inferred in a recent study of Cs and Rb borate glasses [11].…”

Section: Resultssupporting

confidence: 65%

“…For what concerns alkali borate glasses, calculating n c is not a trivial task due to the complex structural changes taking place on addition of alkali oxide. However, values of n c as a function of the alkali-metal oxide molar ratio have been reported that allow describing trends in important properties such as T g [30,33], the fragility [33], and the microhardness [34]. The values for E a (Q max ) are reported as a function of n c in Fig.…”

Section: Resultsmentioning

confidence: 99%

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X-ray induced dynamics in borate glasses with different network connectivity

et al. 2022

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Hard x rays induce atomic dynamics in oxide glasses at doses low enough that the average structure is unchanged. X-ray photon correlation spectroscopy is used here to study this effect in a series of alkali borate glasses characterized by different network connectivity. The product of the x-ray dose rate per atom and the decay time of the density correlation function is a sample-dependent parameter with the dimensions of an energy: It varies between a fraction of eV and few tens of eV and is sensitive to the network connectivity of the glass. It can then be used to access some bonding information also in cases where the x rays perturb the material, a regime of great interest in modern x-ray-based experiments.

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Section: Resultssupporting

confidence: 65%

Section: Resultsmentioning

confidence: 99%

X-ray induced dynamics in borate glasses with different network connectivity

et al. 2022

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“…In contrast to the n BO calculation, one can account for the superstructural units in lithium borate glasses using TCT [77]. However, the correlation between ν and n c when using TCT with and without accounting for superstructural units is similar, although the range of constraints is minimized when accounting for superstructural units (Supplementary Figure S5).…”

Section: Discussionmentioning

confidence: 99%

Structure Dependence of Poisson’s Ratio in Cesium Silicate and Borate Glasses

2020

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In glass materials, Poisson’s ratio (ν) has been proposed to be correlated with a variety of features, including atomic packing density (Cg), liquid fragility (m), and network connectivity. To further investigate these correlations in oxide glasses, here, we study cesium borate and cesium silicate glasses with varying modifier/former ratio given the difference in network former coordination and because cesium results in relatively high ν compared to the smaller alkali modifiers. Within the binary glass series, we find positive correlations between ν on one hand and m and Cg on the other hand. The network former is found to greatly influence the correlation between ν and the number of bridging oxygens (nBO), with a negative correlation for silicate glasses and positive correlation for borate glasses. An analysis based on topological constraint theory shows that this difference cannot be explained by the effect of superstructural units on the network connectivity in lithium borate glasses. Considering a wider range of oxide glasses from the literature, we find that ν generally decreases with increasing network connectivity, but with notable exceptions for heavy alkali borate glasses and calcium alumino tectosilicate glasses.

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“…Topological constraint theory − has been employed to solve many problems in the field of theoretical glass design. − It has successfully predicted the compositional dependence of Vickers hardness, ,− fragility, changes in heat capacity at the glass transition, and glass transition temperature ( T g ). ,− Using the energy landscape approach of Naumis and the Adam–Gibbs model, Mauro et al showed that the ratio of two liquids’ configurational entropies S c is equal to the ratio of their topological degrees of freedom f per atom as follows: , where x is some glass composition and the subscript r denotes a reference value. f is given by where d is the dimensionality of the network and n is the number of constraints per atom.…”

Section: Introductionmentioning

confidence: 99%

Topological Origins of the Mixed Alkali Effect in Glass

et al. 2019

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The mixed alkali effect, the deviation from expected linear property changes when alkali ions are mixed in a glass, remains a point of contention in the glass community. While several earlier models have been proposed to explain mixed alkali effects on ionic motion, models based on or containing discussion of structural aspects of mixed-alkali glasses remain rare by comparison. However, the transition-range viscosity depression effect is many orders in magnitude for mixed-alkali glasses, and the original observation of the effect (then known as the Thermometer Effect) concerned the highly anomalous temperature dependence of stress and structural relaxation time constants. With this in mind, a new structural model based on topological constraint theory is proposed herein which elucidates the origin of the mixed alkali effect as a consequence of network strain due to differing cation radii. Discussion of literature models and data alongside new molecular dynamics simulations and experimental data are presented in support of the model, with good agreement.

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Topological constraint model of high lithium content borate glasses

Cited by 5 publications

References 16 publications

X-ray induced dynamics in borate glasses with different network connectivity

X-ray induced dynamics in borate glasses with different network connectivity

Structure Dependence of Poisson’s Ratio in Cesium Silicate and Borate Glasses

Topological Origins of the Mixed Alkali Effect in Glass

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