High-resolution transmission electron microscopy of pressure-amorphized α-quartz

Winters, Robert R.; Garg, A.; Hammack, William S.

doi:10.1103/physrevlett.69.3751

Cited by 33 publications

(11 citation statements)

References 26 publications

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“…2(e)] shows that the topology is similar to that found in densified glass quenched from high pressure [38]. We conclude that the densified glass obtained in our simulations is a good model for the material recovered in experiments [2,3,5].…”

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confidence: 71%

“…Quartz was reported to collapse into a poorly crystallized metastable structure named quartz II at around 21 GPa [1], i.e., well into the region of stability of stishovite, followed either by amorphization [2][3][4][5][6][7] or by transition to metastable high-density crystalline polymorphs, e.g., P 2 1 /c structure [8][9][10]. The pressure-induced amorphization (PIA) of quartz has been examined either from a thermodynamical point of view (as a density-driven transition to the reentrant highly viscous liquid [2,11], a phenomenology first observed in ice [12]), and from a mechanical standpoint (as an elastic/dynamic instability of the quartz lattice [13][14][15][16][17][18][19][20]), as well as from a crystallographic perspective, as the result of ordering and displacive mechanisms from a common parent structure [21].…”

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confidence: 99%

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Atomistic pathways of the pressure-induced densification of quartz

2015

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When quartz is compressed at room temperature it retains its crystal structure at pressures well above its stability domain (0-2 GPa), and collapses into denser structures only when pressure reaches 20 GPa. Depending on the experimental conditions, pressure-induced densification can be accompanied by amorphization; by the formation of crystalline, metastable polymorphs; and can be preceded by the appearance of an intermediate phase, quartz II, with unknown structure. Based on molecular dynamic simulations, we show that this rich phenomenology can be rationalized through a unified theoretical framework of the atomistic pathways leading to densification. The model emphasizes the role played by the oxygen sublattice, which transforms from a bcc-like order in quartz into close-packed arrangements in the denser structures, through a ferroelastic instability of martensitic nature.

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confidence: 99%

Atomistic pathways of the pressure-induced densification of quartz

2015

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“…The unusual high-pressure behavior of the Si02 polymorph a-quartz and its structural analogs has been the subject of recent experimental [1][2][3][4][5][6][7][8][9][10][11][12] and theoretical [13][14][15][16][17][18][19][20] investigations. Potentially anomalous properties of the material recovered from high pressure have been of particular interest [1][2][3]18,20].…”

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confidence: 99%

“…It is now established that when pressurized well outside of its stability field at 300 K, a-quartz gradually transforms to an amorphous state [1,[3][4][5]7,8]. Despite the growing number of investigations, no detailed in situ structural studies near the onset of amorphization have been reported.…”

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confidence: 99%

New high-pressure transformation in α-quartz

et al. 1993

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Recent experimental and theoretical studies report that quenched pressure-amorphized a-quartz is elastically anisotropic and displays a reversal of anisotropy with respect to the original crystallographic orientation. We demonstrate that samples recovered from static compression experiments of a-quartz exhibit an unusual pressure-induced microstructure, which arises from a new phase transformation in aquartz at 21 GPa. Upon decompression, the high-pressure phase reverts to a quartzlike structure in a twinned state, accounting for the previously reported elastic behavior.

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“…The amorphous nature of samples of pressurized SiC>2 was originally ascertained using x-ray techniques [23]. Initial transmission electron microscopy (TEM) measurements [24] up to 30 GPa showed no evidence of crystallinity and no difference from ordinary "fused" silica. More recent TEM experiments [25,26] show some evidence of remnant crystallinity if the maximum pressure is below 30 GPa.…”

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Memory effects in pressure induced amorphousAlPO4

Polian¹,

Grimsditch

Philippot

1993

Phys. Rev. Lett.

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A Brillouin scattering study of the pressure dependence of the elastic properties of AIPO4 single crystals is presented. On increasing the pressure there is clear evidence of a phase transformation at 15 GPa; this is consistent with previous Raman and x-ray measurements which report an amorphous phase at high pressures. On decreasing the pressure the sample not only recrystallizes at ^ 7 GPa but it reverts to a single crystal with the initial crystallographic orientation. This surprising behavior confirms the claims, based on birefringence measurements, of Kruger and Jeanloz [Science 249, 647 (1990)1. Our results also indicate that, even in the amorphous phase, AIPO4 remains elastically anisotropic.PACS numbers: 6l.50.Ks, 62.50.+p, 78.35,+c Since its relatively recent discovery [1], the phenomenon of pressure induced amorphization has received considerable attention [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The microscopic reasons behind this type of transformation are at present not yet well understood and are being actively investigated using various theoretical and computational modeling techniques [17][18][19][20][21]. Pressure induced amorphization has been found in insulators [1,[4][5][6][7][8][9][10][11][12][13][14], semiconductors [2,3,15], and metals [16]; it is therefore quite a general phenomenon. From the experimental side the effect is still somewhat controversial because it relies on the vanishing of xray or Raman peaks in the experimental spectra and it always can be argued that their disappearance is due to insufficient sensitivity. Phenomenologically the materials can also be classified into two groups, one in which the materials retain their amorphous structure on pressure release and another in which they recrystallize. A similar phenomenon, pressure release amorphization, has also been discovered relatively recently [22].It has been recently shown by Kruger and Jeanloz [10] that AIPO4 belongs to the class of crystals that recrystallize on pressure release. Furthermore, based on the fact that recovered samples had the same birefringence as initial samples, the authors also concluded that the recrystallized samples had the same crystallographic orientation as the starting material and that, in the amorphous phase, it must retain a "memory" of the crystalline phase. The existence of a memory effect was subsequently observed in molecular dynamics calculations [20]. Attempts to further understand this process have concentrated on the sister compound S1O2 quartz which has the same structure (replacing the Al and P atoms by Si) but does not recrystallize on pressure release. Because S1O2 does not recrystallize it allows experiments to be made at atmospheric pressure, greatly simplifying the measurements. The amorphous nature of samples of pressurized SiC>2 was originally ascertained using x-ray techniques [23]. Initial transmission electron microscopy (TEM) measurements [24] up to 30 GPa showed no evidence of crystallinity and no difference from ordinary "fused" silica. More recent TE...

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High-resolution transmission electron microscopy of pressure-amorphized α-quartz

Cited by 33 publications

References 26 publications

Atomistic pathways of the pressure-induced densification of quartz

Atomistic pathways of the pressure-induced densification of quartz

New high-pressure transformation in α-quartz

Memory effects in pressure induced amorphousAlPO4

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