Spin transition in (Mg,Fe)SiO3 perovskite under pressure

Koichiro Umemoto*, Renata M. Wentzcovitch, Yonggang G. Yu, Ryan Requist

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

We present a density functional study of the pressure-induced spin transition in ferrous iron (Fe2+) at the A site in MgSiO3 perovskite. We address the influence of iron concentration and configuration (structural and magnetic), as well as technical issues such as the influence of the exchange-correlation functional (LDA versus GGA) on the spin transition pressure. Supercells containing up to 160 atoms were adopted to tackle these issues. We show that there are preferred configurations for high-spin and low-spin iron and that the spin transition pressure depends strongly on iron concentration and all the issues above. Across the spin transition, irons move into the middle of distorted octahedra causing drastic changes in the d states configuration and a blueshift in the band gap. Such blueshift should decrease the contribution of ferrous iron to the electrical conductivity and increase its contribution to the radiative conductivity in the lower mantle. Both LDA and GGA results suggest that the spin transition can occur in the pressure range of the lower mantle and of previous experiments. The transition range can encompass the entire lower mantle passing through a mixed-spin state caused by cation disorder and magnetic entropy.

Original languageAmerican English
Pages (from-to)198-206
Number of pages9
JournalEarth and Planetary Science Letters
Volume276
Issue number1-2
DOIs
StatePublished - 30 Nov 2008
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank Professor D. Yuen for helpful comments. Calculations in this work were performed using the Quantum-ESPRESSO package ( Baroni et al. ) at the Minnesota Supercomputing Institute and at Indiana University's BigRed system. The spatial distribution of wave functions in Fig. 8 was visualized by XCrySDen ( Kokalj, 2003 ). This research was supported by NSF/EAR-0230319, ITR-0426757 (VLab), NSF/DMR-0325218 (ITAMIT), the UMN-MRSEC, and the Minnesota Supercomputing Institute.

Keywords

  • Atomic and magnetic configurations
  • Ferrous iron
  • First principles
  • Lower mantle
  • Perovskite
  • Spin transition

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