Spin states and hyperfine interactions of iron incorporated in MgSiO 3 post-perovskite

Yonggang G. Yu; Han Hsu; Matteo Cococcioni; Renata M. Wentzcovitch

doi:10.1016/j.epsl.2012.03.002

Spin states and hyperfine interactions of iron incorporated in MgSiO ₃ post-perovskite

Yonggang G. Yu, Han Hsu, Matteo Cococcioni, Renata M. Wentzcovitch

Chemical Engineering and Materials Science

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

Using density functional theory+Hubbard U (DFT+U) calculations, we investigate the spin states and nuclear hyperfine interactions of iron incorporated in magnesium silicate (MgSiO ₃) post-perovskite (Ppv), a major mineral phase in the Earth's D" layer, where the pressure ranges from ~120 to 135GPa. In this pressure range, ferrous iron (Fe ²⁺) substituting for magnesium at the dodecahedral (A) site remains in the high-spin (HS) state; intermediate-spin (IS) and low-spin (LS) states are highly unfavorable. As to ferric iron (Fe ³⁺), which substitutes magnesium at the A site and silicon at the octahedral (B) site to form (Mg,Fe)(Si,Fe)O ₃ Ppv, we find the combination of HS Fe ³⁺ at the A site and LS Fe ³⁺ at the B site the most favorable. Neither A-site nor B-site Fe ³⁺ undergoes a spin-state crossover in the D" pressure range. The computed iron quadrupole splittings are consistent with those observed in Mössbauer spectra. The effects of Fe ²⁺ and Fe ³⁺ on the equation of state of Ppv are found nearly identical, expanding the unit cell volume while barely affecting the bulk modulus.

Original language	English (US)
Pages (from-to)	1-7
Number of pages	7
Journal	Earth and Planetary Science Letters
Volume	331-332
DOIs	https://doi.org/10.1016/j.epsl.2012.03.002
State	Published - May 15 2012

Bibliographical note

Funding Information:
This work is supported by the NSF grants EAR-0810272 , EAR-1047629 , and partially by the MRSEC Program of NSF grants DMR-0212302 and DMR-0819885 . We thank Peter Blaha for valuable discussions on the calculations of EFG via the WIEN2k code. All calculations were performed at the Minnesota Supercomputing Institute (MSI).

Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.

Keywords

D" layer
Equation of state
Fe-bearing post-perovskite (MgSiO )
Ferrous and ferric iron (Fe and Fe )
LDA+U
Lower mantle
Quadrupole splittings
Spin state crossover

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title = "Spin states and hyperfine interactions of iron incorporated in MgSiO 3 post-perovskite",

abstract = "Using density functional theory+Hubbard U (DFT+U) calculations, we investigate the spin states and nuclear hyperfine interactions of iron incorporated in magnesium silicate (MgSiO 3) post-perovskite (Ppv), a major mineral phase in the Earth's D{"} layer, where the pressure ranges from ~120 to 135GPa. In this pressure range, ferrous iron (Fe 2+) substituting for magnesium at the dodecahedral (A) site remains in the high-spin (HS) state; intermediate-spin (IS) and low-spin (LS) states are highly unfavorable. As to ferric iron (Fe 3+), which substitutes magnesium at the A site and silicon at the octahedral (B) site to form (Mg,Fe)(Si,Fe)O 3 Ppv, we find the combination of HS Fe 3+ at the A site and LS Fe 3+ at the B site the most favorable. Neither A-site nor B-site Fe 3+ undergoes a spin-state crossover in the D{"} pressure range. The computed iron quadrupole splittings are consistent with those observed in M{\"o}ssbauer spectra. The effects of Fe 2+ and Fe 3+ on the equation of state of Ppv are found nearly identical, expanding the unit cell volume while barely affecting the bulk modulus.",

keywords = "D{"} layer, Equation of state, Fe-bearing post-perovskite (MgSiO ), Ferrous and ferric iron (Fe and Fe ), LDA+U, Lower mantle, Quadrupole splittings, Spin state crossover",

author = "Yu, {Yonggang G.} and Han Hsu and Matteo Cococcioni and Wentzcovitch, {Renata M.}",

note = "Funding Information: This work is supported by the NSF grants EAR-0810272 , EAR-1047629 , and partially by the MRSEC Program of NSF grants DMR-0212302 and DMR-0819885 . We thank Peter Blaha for valuable discussions on the calculations of EFG via the WIEN2k code. All calculations were performed at the Minnesota Supercomputing Institute (MSI). Copyright: Copyright 2012 Elsevier B.V., All rights reserved.",

year = "2012",

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doi = "10.1016/j.epsl.2012.03.002",

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T1 - Spin states and hyperfine interactions of iron incorporated in MgSiO 3 post-perovskite

AU - Yu, Yonggang G.

AU - Hsu, Han

AU - Cococcioni, Matteo

AU - Wentzcovitch, Renata M.

N1 - Funding Information: This work is supported by the NSF grants EAR-0810272 , EAR-1047629 , and partially by the MRSEC Program of NSF grants DMR-0212302 and DMR-0819885 . We thank Peter Blaha for valuable discussions on the calculations of EFG via the WIEN2k code. All calculations were performed at the Minnesota Supercomputing Institute (MSI). Copyright: Copyright 2012 Elsevier B.V., All rights reserved.

PY - 2012/5/15

Y1 - 2012/5/15

N2 - Using density functional theory+Hubbard U (DFT+U) calculations, we investigate the spin states and nuclear hyperfine interactions of iron incorporated in magnesium silicate (MgSiO 3) post-perovskite (Ppv), a major mineral phase in the Earth's D" layer, where the pressure ranges from ~120 to 135GPa. In this pressure range, ferrous iron (Fe 2+) substituting for magnesium at the dodecahedral (A) site remains in the high-spin (HS) state; intermediate-spin (IS) and low-spin (LS) states are highly unfavorable. As to ferric iron (Fe 3+), which substitutes magnesium at the A site and silicon at the octahedral (B) site to form (Mg,Fe)(Si,Fe)O 3 Ppv, we find the combination of HS Fe 3+ at the A site and LS Fe 3+ at the B site the most favorable. Neither A-site nor B-site Fe 3+ undergoes a spin-state crossover in the D" pressure range. The computed iron quadrupole splittings are consistent with those observed in Mössbauer spectra. The effects of Fe 2+ and Fe 3+ on the equation of state of Ppv are found nearly identical, expanding the unit cell volume while barely affecting the bulk modulus.

AB - Using density functional theory+Hubbard U (DFT+U) calculations, we investigate the spin states and nuclear hyperfine interactions of iron incorporated in magnesium silicate (MgSiO 3) post-perovskite (Ppv), a major mineral phase in the Earth's D" layer, where the pressure ranges from ~120 to 135GPa. In this pressure range, ferrous iron (Fe 2+) substituting for magnesium at the dodecahedral (A) site remains in the high-spin (HS) state; intermediate-spin (IS) and low-spin (LS) states are highly unfavorable. As to ferric iron (Fe 3+), which substitutes magnesium at the A site and silicon at the octahedral (B) site to form (Mg,Fe)(Si,Fe)O 3 Ppv, we find the combination of HS Fe 3+ at the A site and LS Fe 3+ at the B site the most favorable. Neither A-site nor B-site Fe 3+ undergoes a spin-state crossover in the D" pressure range. The computed iron quadrupole splittings are consistent with those observed in Mössbauer spectra. The effects of Fe 2+ and Fe 3+ on the equation of state of Ppv are found nearly identical, expanding the unit cell volume while barely affecting the bulk modulus.

KW - D" layer

KW - Equation of state

KW - Fe-bearing post-perovskite (MgSiO )

KW - Ferrous and ferric iron (Fe and Fe )

KW - LDA+U

KW - Lower mantle

KW - Quadrupole splittings

KW - Spin state crossover

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U2 - 10.1016/j.epsl.2012.03.002

DO - 10.1016/j.epsl.2012.03.002

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SN - 0012-821X

VL - 331-332

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EP - 7

JO - Earth and Planetary Science Letters

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