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Electronic spin state of ferric iron in Al-bearing perovskite in the lower mantle

Li, L; Brodholt, JP; Stackhouse, S; Weidner, DJ; Alfredsson, M; Price, GD; (2005) Electronic spin state of ferric iron in Al-bearing perovskite in the lower mantle. Geophysical Research Letters , 32 (17) , Article L17307. 10.1029/2005GL023045. Green open access

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Abstract

We investigate the effect of pressure on the electronic spin state of ferric iron on Al-bearing MgSiO3-perovskite using first-principle computations. Ferric iron (6.25 mol%) and Al ( 6.25 mol%) substitute for Mg and Si respectively. Five substitution models on different atomic position pairs are examined. Our results show that spin state transition from high spin (HS) to low spin (LS) occurs on the Fe3+ ions at high pressure, while there is no stability field for the intermediate spin state. Fe3+ alone can be responsible for the spin state transition. The five models witness a transition pressure ranging from 97-126 GPa. Differential stress can change the pressure for the spin collapse. The lowest pressure spin state transition occurs where Al3+ and Fe3+ are in adjacent sites. These results are one explanation to the reported experimental observations that the spin transition occurs over a wide pressure range. This finding may have important implications for the dynamics and seismic signature of the lower mantle.

Type: Article
Title: Electronic spin state of ferric iron in Al-bearing perovskite in the lower mantle
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2005GL023045
Publisher version: http://dx.doi.org/10.1029/2005GL023045
Language: English
Additional information: Copyright 2005 by the American Geophysical Union
Keywords: Augmented-wave method, X-ray-diffraction, MgSiO3 perovskite, Earths mantle, High-pressure, Temperature, Mechanism, Strength, GPa
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/99230
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