Pressure-induced structural modulations in coesite
نویسندگان
چکیده
منابع مشابه
Multiple pathways in pressure-induced phase transition of coesite.
High-pressure single-crystal X-ray diffraction method with precise control of hydrostatic conditions, typically with helium or neon as the pressure-transmitting medium, has significantly changed our view on what happens with low-density silica phases under pressure. Coesite is a prototype material for pressure-induced amorphization. However, it was found to transform into a high-pressure octahe...
متن کاملPressure Induced Amorphization in Crystalline Silica: Soft Phonon Modes and Shear Instabilities in Coesite
Quartz and closely related materials will transform under pressure from crystalline states to amorphous forms. Here we examine coesite, a high pressure form of silica which also undergoes pressure induced amorphization. We nd that coesite, like quartz, possesses a shear instability closely coupled to a zone edge phonon softening at pressures comparable to the amorphization transformation. The c...
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Structural modulations affecting a small fraction of the population of plasmalemmal vesicles of vascular endothelia are described. They include forms which are apparently produced by the fusion of the vesicular membrane with the plasmalemma and by the successive elimination of the layers of the two fused membranes. Such modulations are assumed to represent stages in the discharge process of ves...
متن کاملHydrostatic compression and high-pressure elastic constants of coesite silica
Using density-functional theory, we computed all the independent elastic constants of coesite, a high-pressure polymorph of silica, as functions of pressure up to 15 GPa. The results are in good agreement with experimental measurements under ambient conditions. Also, the predicted pressure-dependent elastic properties are consistent with x-ray data in the literature concerning lattice strains a...
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The stability of MgH2 has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure alpha-MgH2 takes a TiO2-rutile-type structure. alpha-MgH2 is predicted to transform into gamma-MgH2 at 0.39 GPa. The calculated structural data for alpha- and gamma-MgH2 are in very good agreement with experimental values. At equilibrium the energy difference between these...
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ژورنال
عنوان ژورنال: Physical Review B
سال: 2018
ISSN: 2469-9950,2469-9969
DOI: 10.1103/physrevb.98.104106