کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6447441 | 1641481 | 2016 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Spin crossover in (Mg,Fe3+)(Si,Fe3+)O3 bridgmanite: Effects of disorder, iron concentration, and temperature
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فیزیک زمین (ژئو فیزیک)
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چکیده انگلیسی
The spin crossover of iron in Fe3+-bearing bridgmanite, the most abundant mineral of the Earth's lower mantle, is by now a well-established phenomenon, though several aspects of this crossover remain unclear. Here we investigate effects of disorder, iron concentration, and temperature on this crossover using ab initio LDAÂ +Â Usc calculations. The effect of concentration and disorder are addressed using complete statistical samplings of coupled substituted configurations in super-cells containing up to 80 atoms. Vibrational/thermal effects on the crossover are addressed within the quasiharmonic approximation. The effect of disorder seems quite small, while increasing iron concentration results in considerable increase in the crossover pressure. Our calculated compression curves for iron-free, Fe2+-, and Fe3+-bearing bridgmanite compare well with the latest experimental measurements. The comparison also suggests that in a closed system, Fe2+ present in the sample may transform into Fe3+ by introduction of Mg and O vacancies with increasing pressure. As in the spin crossover in ferropericlase, this crossover in bridgmanite is accompanied by a clear volume reduction and an anomalous softening of the bulk modulus throughout the crossover pressure range. These effects reduce significantly with increasing temperature. Though the concentration of [Fe3+]Si in bridgmanite may be small, related elastic anomalies may impact the interpretation of radial and lateral velocity structures of the Earth's lower mantle.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 260, November 2016, Pages 53-61
Journal: Physics of the Earth and Planetary Interiors - Volume 260, November 2016, Pages 53-61
نویسندگان
Gaurav Shukla, Renata M. Wentzcovitch,