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SiO 2 phase diagram, modified after 18,26,47 . Shown is experimental data where the structure of SiO 2 was resolved. Indicated are the different equilibrium phase stability fields and the geotherms of Earth and terrestrial planets with a mass of 10 M E . Red diamonds are data from this study and the dashed magenta line indicates the Sesame stishovite EOS 7360 50 . Shown is data with quartz or fused silica as a starting material: black and grey squares from 2 , circles from 10 , right triangles from 12 , lower triangles from 15 and stars from 17 as well as stishovite as a starting material: white squares 4 , upper triangles 27 , crosses 34 and left triangles 28 . Furthermore melting lines are indicated: brown 26 , orange 51 , pink 52 , blue 53 , green 54 and light blue 55,56 .
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SiO2 is one of the most fundamental constituents in planetary bodies, being an essential building block of major mineral phases in the crust and mantle of terrestrial planets (1–10 ME). Silica at depths greater than 300 km may be present in the form of the rutile-type, high pressure polymorph stishovite (P42/mnm) and its thermodynamic stability is...
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Context 1
... results of this study on shock compressed stishovite observed by in-situ X-ray diffraction differ strongly from static compression experiments at respective pressures (Fig. 5). X-ray diffraction studies on stishovite with a DAC show a distinct phase transformation at ~60 GPa to the CaCl 2 type silica 5,34 . This is, however, in contrast to previous shock compression experiments, where the displacive transition towards CaCl 2 does not appear in continuum Hugoniot data [24][25][26] ...
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... compression, due to the absence of phase transformations, shock temperature rises with increasing pressure to adjust to the increase of internal energy due to the compression work 26 . Our calculations indicate, that stishovite is experiencing temperatures ranging from 324 up to 4757 K over a pressure range of 18 to 336 GPa during shock loading (Fig. 5). However, because of the nanosecond timescales during dynamic loading and accommodation of rate-limiting kinetic hinderances, effects can result in significant shifts of equilibrium phase boundaries such that transitions may not be observed or may require significant overpressure. This is a known deviation between shock and static ...
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... pressure and temperature range encompassed in this study is comparable to Super-Earth (1-10 M E ) interior conditions (Fig. 5). However and contrary to our results, it is well established from experimental observation that a stable stishovite structure within the Earth's mantle at pressures exceeding ~60 GPa is improbable 47 . This can be explained by the short timescales (few ns) involved during our shock compression experiments, which can prevent the ...
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The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments...
Citations
... The lattice parameters obtained from our data are compared with those predicted by theory [18] in Fig. 6. Nonhydrostatic stress under dynamic loading may affect the lattice parameters as observed in other studies [40,56,57]. The corresponding densities (shown as blue symbols) are larger than those of the HP-PdF 2 -type phase and are generally consistent with DFT at 0 K (Fig. 5) [18]. ...
... A recent study of laser-shocked polycrystalline stishovite revealed no phase transformations and remarkable persistence of the rutile-type structure to 336 GPa, well beyond its expected stability limit of ∼60 GPa [56]. Furthermore, shock-compression studies on silicates with in situ x-ray diffraction have observed transformation to FIG. 7. Phase diagram of GeO 2 with phase boundaries [60][61][62], estimated Hugoniot of amorphous [63] and rutile-type GeO 2 , and predicted thermodynamic paths. ...
The high-pressure (HP) behavior of dioxides is of interest due to their extensive polymorphism and role as analogs for SiO2, a phase expected to be important in the deep mantles of Earth and terrestrial exoplanets. Here we report on dynamic ramp compression of quartz-type germanium dioxide GeO2 to stresses up to 882 GPa, a higher peak stress than previous studies by a factor of 5. X-ray diffraction data show that HP−PdF2-type GeO2 occurs under ramp loading from 154 to 440 GPa, and this phase persists to higher pressure than predicted by theory. Above 440 GPa, we observe evidence for transformation to a new phase of GeO2. Based on the diffraction data, the best candidate for this new phase is the cotunnite-type structure which has been predicted to be a stable phase of GeO2 above 300 GPa. The HP−PdF2-type and cotunnite-type structures are important phases in a wide range of AX2 compounds, including SiO2, at multihundred GPa stresses. Our results demonstrate that ramp compression can be an effective technique for synthesizing and characterizing such phases in oxides. In addition, we show that pulsed x-ray diffraction under ramp compression can be used to examine lower-symmetry phases in oxide materials.
... 70,71 Because alloying may affect melting temperature and crystalline structure, it is important to conduct experiments not only on the pure elements but also on more representative Fe-Ni alloys. 72 Silicates, an important component of the mantles of terrestrial planets, have also been extensively studied under shock compression both experimentally [73][74][75] and using numerical methods. 76,77 SiO 2 shows a large polymorphism and its behavior under pressure is fairly well understood below 200 GPa. ...
... Previous experimental studies have shown that an instantaneous overpressurization in a DAC can shift the phase transitions α-cristobalite, cristobalite II and cristobalite X-I to higher pressures [27,28]. Other dynamic compression studies on SiO 2 using membrane DACs, gas guns, or optical lasers have also found that fast compression rates can shift or even hinder high pressure phase transitions [38][39][40][41]. It was reported, for instance, that by using crystalline SiO 2 (α-quartz) as the starting material in a membrane DAC, the high pressure phase transition α-quartz → stishovite shifted towards pressures of up to 18-38 GPa [38] when compressed rapidly, much higher than expected from its 064109-3 steady state equilibrium transition pressure (∼7 GPa) [2,8]. ...
... In another study, high-pressure phase transitions were not observed when stishovite was used as starting material in a laser-induced compression experiment [41]. Previous works suggested that rapidly compressed solids depend strongly on the strain rate of the compression, and consequently, higher transition pressures can be achieved through higher strainrate drives [42,43]. ...
In this study we present results of the dynamic compression of α-cristobalite up to a pressure of 106 GPa with the use of the dynamic diamond anvil cell. X-ray diffraction images were recorded at different ramp compression and decompression rates to investigate in situ the high-pressure phase transitions of α-cristobalite. Our results suggest that the pressure onset of the phase transformation of α-cristobalite to cristobalite II, cristobalite X-I, and ultimately to seifertite (α-PbO 2 type SiO 2) is dependent on the applied compression rates and stress conditions of the experiment. Increasing compression rates in general shift the studied phase transitions to higher pressures. Furthermore, our results indicate for single crystals under hydrostatic conditions a suppression of a phase transition from cristobalite X-I to seifertite at pressures of up to 82 GPa.
... Tracking this parameter could provide insight into which important underlying physical or chemical properties (e.g., starting structure, composition, and microstructure like crystal orientation or texture) and/or processes (e.g., static vs. dynamic compression, including strain rate) dictate the deformation response in meteoritic material-including the typical timescales of phase transformation of meteorites exposed to extreme conditions. High-pressure dynamic compression experiments represent a unique way to recreate dynamic processes such as asteroid/planetary collisions in the lab and make it possible to track the lattice-level response of materials using in situ time-resolved X-ray diffraction [21,22]. Dynamic compression techniques also provide access to combined high-pressure and hightemperature states of a material in concert with characterization via ultrafast X-ray probes that more traditional static compression techniques cannot access, e.g., [23]. ...
... This plastic smooths out any inhomogeneities (e.g., hot spots) in the drive laser to generate a planar, uniform shock front with respect to the X-ray probed volume. [21,22]. Dynamic compression techniques also provide access to combined high-pressure and high-temperature states of a material in concert with characterization via ultrafast Xray probes that more traditional static compression techniques cannot access, e.g., [23]. ...
Natural kamacite samples (Fe92.5Ni7.5) from a fragment of the Gibeon meteorite were studied as a proxy material for terrestrial cores to examine phase transition kinetics under shock compression for a range of different pressures up to 140 GPa. In situ time-resolved X-ray diffraction (XRD) data were collected of a body-centered cubic (bcc) kamacite section that transforms to the high-pressure hexagonal close-packed (hcp) phase with sub-nanosecond temporal resolution. The coarse-grained crystal of kamacite rapidly transformed to highly oriented crystallites of the hcp phase at maximum compression. The hcp phase persisted for as long as 9.5 ns following shock release. Comparing the c/a ratio with previous static and dynamic work on Fe and Fe-rich Fe-Ni alloys, it was found that some shots exhibit a larger than ideal c/a ratio, up to nearly 1.65. This work represents the first time-resolved laser shock compression structural study of a natural iron meteorite, relevant for understanding the dynamic material properties of metallic planetary bodies during impact events and Earth’s core elasticity.
Разработаны уравнения состояния сапфира, кремнезема, периклаза и рутила, применимые в широкой области давлений и плотностей. Приводятся результаты сопоставления с имеющимися данными, полученными при высоких давлениях в ударно-волновых экспериментах для кристаллических и пористых образцов.
An integrated Equation of State (EOS) and strength/pore‐crush/damage model framework is provided for modeling near to source (near‐field) ground‐shock response, where large deformations and pressures necessitate coupling EOS with pressure‐dependent plastic yield and damage. Nonlinear pressure‐dependence of strength up to high‐pressures is combined with a Modified Cam‐Clay‐like cap‐plasticity model in a way to allow degradation of strength from pore‐crush damage, what we call the “Yp‐Cap” model. Nonlinear hardening under compaction allows modeling the crush‐out of pores in combination with a fully saturated EOS, that is, for modeling partially saturated ground‐shock response, where air‐filled voids crush. Attention is given to algorithmic clarity and efficiency of the provided model, and the model is employed in example numerical simulations, including finite element simulations of underground explosions to exemplify its robustness and utility.
This article reviews our experimental investigation of the phase transformation process of 304 austenitic stainless steel (SUS304) in the laser peening process. An optical laser pump–X-ray free-electron laser probe in-situ time-resolved X-ray diffraction measurement reveals the formation process of α ′-martensite from γ -austenite of SUS304 under shock compression and release, which occur during the laser peening process. The result indicates that fast tensile strain rate deformation, arising from shock pressure release waves, drives a considerable amount of the transformation to transient ε -martensite from γ - austenite, where the transient ε -martensite acts as an intermediate phase of the transformation to α ′-martensite.
High pressure mineral physics is a field that has shaped our understanding of deep planetary interiors and revealed new material phenomena occurring at extreme conditions. Comprised of sixteen chapters written by well-established experts, this book covers recent advances in static and dynamic compression techniques and enhanced diagnostic capabilities, including synchrotron X-ray and neutron diffraction, spectroscopic measurements, in situ X-ray diffraction under dynamic loading, and multigrain crystallography at megabar pressures. Applications range from measuring equations of state, elasticity, and deformation of materials at high pressure, to high pressure synthesis, thermochemistry of high pressure phases, and new molecular compounds and superconductivity under extreme conditions. This book also introduces experimental geochemistry in the laser-heated diamond-anvil cell enabled by the focused ion beam technique for sample recovery and quantitative chemical analysis at submicron scale. Each chapter ends with an insightful perspective of future directions, making it an invaluable source for graduate students and researchers.
