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Showing 1 to 9 of 9 for “"stishovite"”.
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Elasticity across the post-stishovite transition in subducted basalt
… In this dissertation, physical properties of stishovite and CaCl₂-type post-stishovite, which are abundant MORB components, have been determined at high pressure in order to study geophysical consequences across the post-stishovite transition in MORB. Specifically, I measured sound velocities …
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Elasticity and phase transitions of stishovite and NaCl at high pressure
… determination of the elasticity and stability of stishovite, the high-pressure silica polymorph, as a major constituent of the MORB layer of subducting lithospheric slabs. These thin (∼10km thick) layers subducted into the Earth mantle create regions of thermal, compositional and, hence, …
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Density Functional Theory Study of Rutile SiO₂ Stishovite: An Electron Pair Description of Bulk and Surface Properties
… the nonpolar, stoichiometric (110) surface of stishovite, rutile structure type SiO₂, has been studied using a first principles, density functional method. The geometric and electronic structure, including the density of states, charge density, and electron localization function for both the …
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The response of polyhedra in close packed structures to temperature and pressure
… show an increased distortion while those in stishovite show a decreased distortion with increasing T. An analysis of apparent bulk moduli and linear thermal expansion coefficients calculated for the constituent polyhedra shows that the distortion of a material with a close packed structure is …
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The X-discontinuity: Seismic signatures of a heterogeneous upper mantle
… of the X in mantle plume settings to the coesite-stishovite phase transition and/or the presence of carbonated silicate melt, shedding insight into the nature of mantle plumes and their role in mantle convection. I study the presence of the X beneath Africa, using continuous observations and a …
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Geochemical Insights into Earth Materials from Quantum Mechanical Computation
… anhydrous, and the high H2O storage capacity of stishovite in oceanic crust provides a potential conduit for water transport into the lower mantle. The possible mechanisms of incorporating water in stishovite have been simulated via ab initio calculations in supercells containing different water …
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Diversity of compressional mechanisms among SiO2 polymorphs : case of coesite and cristobalite
… sufficient to form the thermodynamically stable stishovite. In non-hydrostatic conditions in the presence of uniaxial stress, cristobalite eventually transforms to seifertite-like SiO2, which is quenchable. Thus, according to our results, presence of seifertite may not always require the minimum …
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Diversity of compressional mechanisms among SiO<sub>2</sub> polymorphs : case of coesite and cristobalite.
… sufficient to form the thermodynamically stable stishovite. In non-hydrostatic conditions in the presence of uniaxial stress, cristobalite eventually transforms to seifertite-like SiO<sub>2</sub>, which is quenchable. Thus, according to our results, presence of seifertite may not always require …
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(Na,K) Aluminosilicate Hollandites: Structures, Crystal Chemistry, and High-pressure Behaviour
… a pure hollandite phase (and maximum 1-2% of stishovite) were synthesized at temperature of 1700 °C and different pressures with up to 50% of NaAlSi3O8 component. No pure NaAlSi3O8 hollandite end-member was succsessfully synthesized. Considering the difference in heat dissipation between the …