High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

Prakapenka, Vitali; Shen, Guoyin; Dubrovinsky, Leonid; Rivers, Mark L.; Sutton, S. R.

doi:10.1016/j.jpcs.2003.12.019

Cited by 122 publications

(140 citation statements)

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“…The quartz II and the new phase with space group P2 1 =c appeared around 19-21 GPa in a quasihydrostatic pressure medium and both phases persisted stably up to 40 GPa [35]. Prakapenka et al [34] detected that quartz transforms above 16 GPa to quartz II and above 22 GPa to a monoclinic structure with space group P2 1 =c without amorphization. Around 55 GPa, this monoclinic structure transforms to the CaCl 2 structure and at higher pressures to α-PbO 2 and to pyrite-type (Pa 3) structures [34].…”

Section: Examplesmentioning

confidence: 99%

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Second harmonic generation measurements at high pressures on powder samples

Bayarjargal

Winkler

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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This article reviews the most recent results concerning second harmonic generation (SHG) experiments of non-phase matchable and phase matchable powder samples at high pressures and explains the pressure dependence of the intensity of the SHG signal by correlating it to the ratio between the average coherence length and the average particle size. The examples discussed here include pressure-induced structural changes in quartz, ZnO, ice VII and KIO 3 . It is shown that the second harmonic generation technique is a unique tool for the detection of pressure-induced structural phase transitions. It is laboratory based and allows fast measurements. It is complementary to X-ray diffraction and provides additional information about the presence of an inversion center for unknown or controversially discussed structures at high pressure.

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Section: Examplesmentioning

confidence: 99%

“…Prakapenka et al [34] detected that quartz transforms above 16 GPa to quartz II and above 22 GPa to a monoclinic structure with space group P2 1 =c without amorphization. Around 55 GPa, this monoclinic structure transforms to the CaCl 2 structure and at higher pressures to α-PbO 2 and to pyrite-type (Pa 3) structures [34].…”

Section: Examplesmentioning

confidence: 99%

Second harmonic generation measurements at high pressures on powder samples

Bayarjargal

Winkler

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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“…In particular, this behavior has enormous implications as the electronic properties are substantially modified with the change of TM coordination, but also in geophysics as the ample polymorphism attained in the Earth, where SiO 2 quartz is an example of this behavior. [15][16][17] The ambient pressure quartz-coesite structure, which is characterized by a three-dimensional (3D) network of O-sharing SiO 4− 4 tetrahedra, transforms to the stishovite phase at high pressure, which is the high-pressure polymorph of the rutile structure. This last phase has called a large attention since it appears in the Earth's lower mantle.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced phase-transition sequence in CoF2: An experimental and first-principles study on the crystal, vibrational, and electronic properties

et al. 2013

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We report a complete structural study of CoF 2 under pressure. Its crystal structure and vibrational and electronic properties have been studied both theoretically and experimentally using first-principles density functional theory (DFT) methods, x-ray diffraction, x-ray absorption at Co K-edge experiments, Raman spectroscopy, and optical absorption in the 0-80 GPa range. We have determined the structural phase-transition sequence in CoF 2 and corresponding transition pressures. The results are similar to other transition-metal difluorides such as FeF 2 but different to ZnF 2 and MgF 2 , despite that the Co 2+ size (ionic radius) is similar to Zn 2+ and Mg 2+ . We found that the complete phase-transition sequence is tetragonal rutile (P 4 2 /mnm) → CaCl 2 type (orthorhombic P nnm) → distorted PdF 2 (orthorhombic P bca) + PdF 2 (cubic P a3) in coexistence → fluorite (cubic F m3m) → cotunnite (orthorhombic P nma). It was observed that the structural phase transition to the fluorite at 15 GPa involves a drastic change of coordination from sixfold octahedral to eightfold cubic with important modifications in the vibrational and electronic properties. We show that the stabilization of this high-pressure cubic phase is possible under nonhydrostatic conditions since ideal hydrostaticity would stabilize the distorted-fluorite structure (tetragonal I 4/mmm) instead. Although the first rutile → CaCl 2 -type second-order phase transition is subtle by Raman spectroscopy, it was possible to define it through the broadening of the E g Raman mode which is split in the CaCl 2 -type phase. First-principles DFT calculations are in fair agreement with the experimental Raman mode frequencies, thus providing an accurate description for all vibrational modes and elastic properties of CoF 2 as a function of pressure.

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“…Stishovite was synthesized from the flint and compressed in two experimental DAC runs up to 23 and 38 GPa at HPCAT (sector 16-ID-B) and GSECARS (sector 13-ID-D) beamlines, respectively, of the Advanced Photon Source (APS) at Argonne National Laboratory. We laser-heated samples at pressures of 13-16 GPa in order to activate kinetics and transition quartz directly to stishovite without first transitioning to coesite or intermediate metastable SiO 2 phases that have previously been observed to nucleate at room temperature and ~21 GPa (e.g., Haines et al 2001;Kingma et al 1996;Prakapenka et al 2004). We performed experiments in radial diffraction geometry (e.g., Wenk et al 2006) rather than axial geometry in order to see variations in diffraction intensities as a function of the azimuthal angle η on Debye rings (the angle with respect to the compression direction; η = 90° is labeled in Fig.…”

Section: Methodsmentioning

confidence: 99%