Pressure effect on the electronic structure of iron in (Mg,Fe)(Al,Si)O3 perovskite: A combined synchrotron M?ssbauer and x-ray emission spectroscopy study up to 100 GPa

Journal Article · Mon Jan 23 04:00:00 EST 2006 · Physics and Chemistry Minerals, vol. 33, no. 8-9, September 5, 2006, pp. 575-585

DOI:https://doi.org/10.1007/s00269-006-0105-y· OSTI ID:898500

Li, J; Sturhahn, W; Jackson, J; Struzhkin, V V; Lin, J F; Zhao, J; Mao, H K; Shen, G

We investigated the valence and spin state of iron in an Al-bearing ferromagnesian silicate perovskite sample, (Mg{sub 0.88}Fe{sub 0.09})(Si{sub 0.94}Al{sub 0.10})O{sub 3}, at 300 K and up to 100 GPa, using diamond-anvil cells and synchrotron Moessbauer spectroscopy techniques. Under elevated pressures, our Moessbauer time spectra are sufficiently fitted by a ''three-doublet'' model, which assumes two ferrous (Fe{sup 2+}) iron types and one ferric (Fe{sup 3+}) iron type with distinct hyperfine parameters. At pressures above 20 GPa, the fraction of the ferric iron, Fe{sup 3+}/{Sigma}Fe, is about 75% and remains unchanged to the highest pressure, indicating a fixed valence state of iron within this pressure range. Between 20 and 100 GPa, the quadruple splittings of all three iron types do not change with pressure, while the isomer shift between the Fe{sup 3+} types and the Fe{sup 2+} type increases continuously with increasing pressure. In conjunction with previous x-ray emission data on the same sample, the unchanging quadruple splittings and increasing isomer shift suggest that Fe{sup 2+} undergoes a broad spin crossover towards the low-spin state at 100 GPa, while Fe{sup 3+} remains in the high-spin state. The essentially constant quadruple splittings of Fe{sup 2+} can also be taken as an indication for strong resistance against further distortion of the local iron environment after initial compression.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 898500
• Report Number(s): UCRL-JRNL-218577
• Journal Information: Physics and Chemistry Minerals, vol. 33, no. 8-9, September 5, 2006, pp. 575-585, Journal Name: Physics and Chemistry Minerals, vol. 33, no. 8-9, September 5, 2006, pp. 575-585
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
58 GEOSCIENCES
COMPRESSION
ELECTRONIC STRUCTURE
EMISSION SPECTROSCOPY
HIGH SPIN STATES
IRON
ISOMER SHIFT
MOESSBAUER EFFECT
PEROVSKITE
PRESSURE DEPENDENCE
PRESSURE RANGE
SILICATES
SPECTRA
SPIN
SYNCHROTRONS
VALENCE