Post-pyrite transition in SiO2

Details Post-pyrite transition in SiO2 Post-pyrite transition in SiO2

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p21a1584h&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P21A-1584

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[0500] Computational Geophysics, [3620] Mineralogy And Petrology / Mineral And Crystal Chemistry, [3924] Mineral Physics / High-Pressure Behavior, [6296] Planetary Sciences: Solar System Objects / Extra-Solar Planets

Scientific paper

Here we propose a new phase of SiO2 beyond the pyrite-type phase. SiO2 is one of the most important minerals in Earth and planetary sciences. So far, the pyrite-type phase has been identified experimentally as the highest-pressure form of SiO2. In solar giants and extrasolar planets whose interior pressures are considerably higher than that on Earth, a post-pyrite transition in SiO2 may occur at ~ 1 TPa as a result of the dissociation of MgSiO3 post-perovskite into MgO and SiO2 [Umemtoto et al., Science 311, 983 (2006)]. Several dioxides considered to be low-pressure analogs of SiO2 have a phase with cotunnite-type (PbCl2-type) structure as the post-pyrite phase. However, a first-principles structural search using a genetic algorithm shows that SiO2 should undergo a post-pyrite transition to a hexagonal phase, not to the cotunnite phase. The hexagonal phase is energetically very competitive with the cotunnite-type one. This work was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering and NSF under ATM-0428774 (VLab), EAR-0757903, and EAR-1019853. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358. The computations were performed at the National Energy Research Supercomputing Centre (NERSC) and the Minnesota Supercomputing Institute (MSI).

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