Helium penetrates into silica glass and reduces its compressibility

Sato, Tomoko; Funamori, Nobumasa; Yagi, T.

doi:10.1038/ncomms1343

Cited by 91 publications

(111 citation statements)

References 37 publications

(83 reference statements)

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“…No imagery vibration modes are found for those transition intermediates in the Brillouin zone, confirming they are indeed metastable in the pressure range of interest. These metastable phases match the experiment results in the same pressure range (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), in which the four sets of diffraction patterns can be explained by the formation of the metastable structures in an on-going phase transition. Two of the metastable structures from our experiment also show that the lattice parameter in the b-axis continues to decrease and the c-axis is greatly softened, which is exactly reproduced by our simulation.…”

Section: Resultssupporting

confidence: 72%

“…Helium gas was used as the pressure medium in our experiments. It has been pointed out previously that the injection of helium atoms into large interstitial sites make occur in SiO 2 glass 29,30 , cristobalite 31 and zeolite 32 . For example, in SiO 2 glass and cristobalite, helium atoms can penetrate into the six-membered rings.…”

Section: Discussionmentioning

confidence: 99%

“…At ambient conditions, the coesite ISSs are 53% smaller than cristobalite's measured in volume, which renders it rather difficult for helium atoms to penetrate into the ISSs of coesite. Experimentally, the penetration of He atoms into the solids would result in noticeable changes of the compressibility of the materials 29,30 . In our experiment, all diffraction peaks shifts normally, and no dramatically changes of compressibility of coesite were found.…”

Section: Discussionmentioning

confidence: 99%

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Polymorphic phase transition mechanism of compressed coesite

Shu

Cadien

et al. 2015

Nat Commun

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Silicon dioxide is one of the most abundant natural compounds. Polymorphs of SiO 2 and their phase transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Here, compressing single-crystal coesite SiO 2 under hydrostatic pressures of 26-53 GPa at room temperature, we discover a new polymorphic phase transition mechanism of coesite to post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modelling. The transition features the formation of multiple previously unknown triclinic phases of SiO 2 on the transition pathway as structural intermediates. Coexistence of the low-symmetry phases results in extensive splitting of the original coesite X-ray diffraction peaks that appear as dramatic peak broadening and weakening, resembling an amorphous material. This work sheds light on the long-debated pressure-induced amorphization phenomenon of SiO 2 , but also provides new insights into the densification mechanism of tetrahedrally bonded structures common in nature.

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Section: Resultssupporting

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Polymorphic phase transition mechanism of compressed coesite

Shu

Cadien

et al. 2015

Nat Commun

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“…This random insertion method can successfully reproduce the compression behavior of He-stuffed silica glass as observed in experiments [30][31][32] (Fig. 2).…”

Section: B Molecular Dynamic Simulationsmentioning

confidence: 79%

“…The inclusion of He atoms into silica network substantially suppresses the volume shrinkage under pressure, which is observed in both our MD simulations and in experiments. [30][31][32] Na 2 O-SiO 2 glass samples with a system size of 3000 atoms of compositions ranging from 0 to 40% Na 2 O were prepared by the melt-quench process. Atoms were placed randomly in the simulation box such that they satisfy the composition requirements, with a Gaussian velocity distribution assigned to them so that the system temperature is 300 K. The system was then heated to around 5000 K in the NVT ensemble at a heating rate of 50 K/ps.…”

Section: B Molecular Dynamic Simulationsmentioning

confidence: 99%

Tailoring structure and properties of silica glass aided by computer simulation

et al. 2016

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By using a combination of experiments and molecular dynamics simulations, our studies show that the elastic response of silica glass to initial compression gradually changes from abnormal to normal with increasing quench pressure, helium content or alkali modifier added in the glass matrix. We uncovered the structural origin of the elastic anomaly in silica glass as localized structural transitions between motifs of different stiffness that are similar to those found in its crystalline counterparts. Pressure-quenching, helium-stuffing, or alkali-modifying plays a different role in changing the structure of silica glass, but all of the resulting structures reduce the propensity for such local structural transitions to take place, thus the degree of elastic anomaly. Our studies demonstrate that by processing in ways that gradually eliminates the elastic anomaly, the degree of silica glass to undergo irreversible densification can be eventually eradicated. This provides a solid foundation for the bottom-up design of new glasses with tunable structure and properties.

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Abnormal acoustic wave velocities in basaltic and (Fe,Al)‐bearing silicate glasses at high pressures

Liu

Lin

2014

Geophysical Research Letters

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We have measured acoustic V P and V S velocities of (Fe,Al)-bearing MgSiO 3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)-bearing and basaltic silicate glasses display decreased V P and V S with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO 3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low-velocity zone may be smaller than previously thought.

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Helium penetrates into silica glass and reduces its compressibility

Cited by 91 publications

References 37 publications

Polymorphic phase transition mechanism of compressed coesite

Polymorphic phase transition mechanism of compressed coesite

Tailoring structure and properties of silica glass aided by computer simulation

Abnormal acoustic wave velocities in basaltic and (Fe,Al)‐bearing silicate glasses at high pressures

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