TY - JOUR
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).
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
UR - http://www.scopus.com/inward/record.url?scp=84860510066&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2012.03.002
DO - 10.1016/j.epsl.2012.03.002
M3 - 期刊論文
AN - SCOPUS:84860510066
SN - 0012-821X
VL - 331-332
SP - 1
EP - 7
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -