Al Coordination Changes in High-Pressure Aluminosilicate Liquids

Yarger, Jeffery L.; Smith, K. H.; Nieman, Ronald A.; Diefenbacher, Jason; Wolf, George H.; Poe, Brent T.; McMillan, Paul F.

doi:10.1126/science.270.5244.1964

Cited by 191 publications

(184 citation statements)

References 38 publications

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“…It can be observed that the characteristic distance d decreases with density, which suggests a decrease of the medium range order (MRO). On the contrary, the correlation length L does not follow a general behavior with density since it shows a density window between 2.3 and 3.3 g/cm 3 with a maximum at 2.7 g/cm 3 . We notice that the density of the maximum of L corresponds to the density of the beginning of the growth of the Si V fraction (see Fig.…”

Section: First Sharp Diffraction Peakmentioning

confidence: 99%

“…As a consequence, the model of the network modifier Na atom simply given by stoichiometry (one Na atom involving the appearance of one NBO atom) does not remain valid for ̺ > 3 g/cm 3 . Ultimately, O III are found at high density and their fraction grows up to nearly 50% at ̺ = 5.5 g/cm 3 . Note that 3-fold O atoms (termed triclusters) have already been found both in experiments and in simulations, for example in aluminosilicate glasses 40 .…”

Section: Coordination Numbersmentioning

confidence: 99%

“…3b. The fraction of O I drops for densities larger than ̺ = 2.6 g/cm 3 . At this density, the fraction of O II starts to increase, reaches a maximum at ̺ = 3.8 g/cm 3 and decreases at higher density.…”

Section: Coordination Numbersmentioning

confidence: 99%

“…This trend is consistent with X-ray diffraction results from Benmore in densified silica. 65 Interestingly, the FHWM of the FSDP exhibits a density window between 2.3 and 3.3 g/cm 3 with a minimum found at ̺ = 2.7 g/cm 3 . Coming back to the real space correlations, the FSDP peak position Q FSDP is usually related to a characteristic repeat distance d = 2π/Q FSDP and the FWHM to a correlation length L = 2π/FWHM, sometimes also called 'coherence length', due to atomic density fluctuations 66,67 .…”

Section: First Sharp Diffraction Peakmentioning

confidence: 99%

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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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Section: First Sharp Diffraction Peakmentioning

confidence: 99%

Section: Coordination Numbersmentioning

confidence: 99%

Section: Coordination Numbersmentioning

confidence: 99%

Section: First Sharp Diffraction Peakmentioning

confidence: 99%

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

Bauchy

2012

The Journal of Chemical Physics

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“…N etwork-forming structural motifs such as AO 3 triangular units and AO 4 tetrahedra, where A denotes an electropositive chemical species such as B, Si, or Ge, govern topological ordering in liquid and amorphous oxide materials and therefore have a profound effect on their physical properties (1,2). Examples range from the dependence on network connectivity of the transport properties (e.g., viscosity) of glass-forming and/or magma-related oxide melts (3)(4)(5)(6)(7) to the role played by atomic packing in determining the elastic behavior of glass (8)(9)(10).…”

mentioning

confidence: 99%

Packing and the structural transformations in liquid and amorphous oxides from ambient to extreme conditions

Zeidler

Salmon

Skinner

2014

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

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Liquid and glassy oxide materials play a vital role in multiple scientific and technological disciplines, but little is known about the part played by oxygen-oxygen interactions in the structural transformations that change their physical properties. Here we show that the coordination number of network-forming structural motifs, which play a key role in defining the topological ordering, can be rationalized in terms of the oxygen-packing fraction over an extensive pressure and temperature range. The result is a structural map for predicting the likely regimes of topological change for a range of oxide materials. This information can be used to forecast when changes may occur to the transport properties and compressibility of, e.g., fluids in planetary interiors, and is a prerequisite for the preparation of new materials following the principles of rational design. Examples range from the dependence on network connectivity of the transport properties (e.g., viscosity) of glass-forming and/or magma-related oxide melts (3-7) to the role played by atomic packing in determining the elastic behavior of glass (8-10). In the case of open glass-forming structures, the network connectivity often follows from Zachariasen's rules (11), but there is no reliable guide for predicting the conditions under which transformations occur in the character of network-forming motifs, e.g., from AO 3 to AO 4 or from AO 4 to AO 6 polyhedra.With increasing density, oxygen-oxygen interactions are expected to manifest themselves in the structural transformations that occur (12), but the nature of this role is unknown. For example, the oxygen atom number density ρ O will depend on the type of network-forming motifs, can be altered by adding network modifiers, and will increase with density. Nevertheless, a plot of ρ O versus the measured mean A-O coordination number n O A for network-forming structural motifs does not offer a basis for generalization (Fig. 1). It will be shown, however, that if the data are scaled by the volume occupied by an oxide ion V O , and an adjustment is made for the volume occupied by any network-modifying atoms (i.e., atoms other than oxygen that are not at the centers of network-forming motifs), then the resultant oxygenpacking fraction η O does offer a means for rationalizing the structural transformations that occur. An important proviso is that a constant oxide ion size cannot be assumed. Instead, the oxide ion environment has a profound influence as evidenced by the instability of these ions in the gas phase but their omnipresence in condensed matter (13,14). This variability was recognized in the construction of well-known tables of ionic radii (15, 16), although a constant size was assumed for a given oxide ion coordination number. The variability of the oxide ion size is also a key theme in the development of transferable aspherical ion models which have been successful in accounting for many of the structure-related properties of oxide materials (13,14). In the following we use an empirical approach to tac...

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Quadrupolar NMR in Earth Sciences

Stebbins

2011

Encyclopedia of Magnetic Resonance

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Al Coordination Changes in High-Pressure Aluminosilicate Liquids

Cited by 191 publications

References 38 publications

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

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

Packing and the structural transformations in liquid and amorphous oxides from ambient to extreme conditions

Quadrupolar NMR in Earth Sciences

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