ab initio calculations;
band structure;
Earth mantle;
high-pressure effects;
iron compounds;
magnesium compounds;
magnetic transitions;
XANES;
ABSORPTION-SPECTROSCOPY;
MOSSBAUER-SPECTROSCOPY;
SYNCHROTRON MOSSBAUER;
OXIDATION-STATE;
SPIN TRANSITION;
IRON;
TEMPERATURE;
SPECTRA;
D O I:
10.1103/PhysRevB.79.174115
中图分类号:
T [工业技术];
学科分类号:
08 ;
摘要:
Seven iron-containing oxides and silicates including (Mg-0.88,Fe-0.12)SiO, (Mg-0.86,Fe-0.14)(Si-0.98,Al-0.02)O-3 perovskites, and (Mg-0.80,Fe-0.20) ferropericlase were studied using Fe K-edge x-ray absorption near edge spectroscopy under pressure up to 85 GPa at ambient temperature. First-principles calculations of Fe K-edges of (Mg-0.88,Fe-0.12)SiO perovskite and (Mg-0.80,Fe-0.20)O ferropericlase were performed using a spin-dependent method. The amount and quality of the data collected allows performance of a systematic study of the absorption edge features as a function of pressure in these geophysically important systems, providing direct experimental validation for band-structure calculations. The comparison between experiment and theory allows analyzing in detail the effect of Fe valence and spin state modifications on the spectra, allowing to confirm qualitatively the presence of a pressure induced spin pairing transition in (Mg,Fe)O ferropericlase and a high-spin intermediate spin crossover in (Mg,Fe)(Si,Al)O-3 perovskite.
机构:
CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USACALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA
Ma, Chi
Tschauner, Oliver
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机构:
Univ Nevada, Dept Geosci, Las Vegas, NV 89154 USA
Univ Nevada, High Pressure Sci & Engn Ctr, Las Vegas, NV 89154 USACALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA