Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa

Sang-Heon Shim, Atsushi Kubo, Thomas S. Duffy

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Raman spectra of the perovskite (Pv) and post-perovskite (PPv) phases of MgGeO3 were measured in the laser-heated diamond cell up to 123 GPa. Between 14 and 51 GPa we observed a total of seven Pv modes, the frequencies and relative intensities of which are similar to MgSiO3-Pv with systematically lower frequencies. We also observe a total of ten PPv modes which are much more intense than Pv modes, indicating strong polarizability of the bonds in PPv. The observed Raman mode frequency range of PPv extends to much higher frequencies than Pv, which can be related to the edge sharing of the GeO6 octahedra in PPv which would make Ge-O bonds stronger. The spectroscopic Grüneisen parameters of Pv and PPv are constrained to be 1.56 ± 0.10 and 1.15 ± 0.06, respectively, at the PPv transition. We also estimated that the thermal expansion parameter decreases by 25 ± 10% across the PPv transition. If a similar change occurs in MgSiO3, the low thermal expansivity would dynamically stabilize the PPv layer at the lowermost mantle. Using our Raman measurements and a Kieffer-type model, the Clapeyron slope of the PPv transition is constrained to be + 20 ± 10 MPa/K. The strong positive slope is consistent with the prediction for MgSiO3 and is related to a positive shift of phonon density of states at high-frequency region resulting from the formation of the edge sharing among the GeO6 (or SiO6) octahedra in PPv.

Original languageEnglish (US)
Pages (from-to)166-178
Number of pages13
JournalEarth and Planetary Science Letters
Volume260
Issue number1-2
DOIs
StatePublished - Aug 15 2007
Externally publishedYes

Fingerprint

perovskite
Raman spectroscopy
slopes
thermal expansion
Earth mantle
frequency ranges
diamonds
Raman spectra
low frequencies
shift
predictions
cells
lasers
Diamond
diamond

Keywords

  • Clapeyron slope
  • Grüneisen parameter
  • perovskite
  • post-perovskite
  • Raman spectroscopy
  • thermal expansivity

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)

Cite this

Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa. / Shim, Sang-Heon; Kubo, Atsushi; Duffy, Thomas S.

In: Earth and Planetary Science Letters, Vol. 260, No. 1-2, 15.08.2007, p. 166-178.

Research output: Contribution to journalArticle

@article{5081bd49704a474e807a9928198c9389,
title = "Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa",
abstract = "Raman spectra of the perovskite (Pv) and post-perovskite (PPv) phases of MgGeO3 were measured in the laser-heated diamond cell up to 123 GPa. Between 14 and 51 GPa we observed a total of seven Pv modes, the frequencies and relative intensities of which are similar to MgSiO3-Pv with systematically lower frequencies. We also observe a total of ten PPv modes which are much more intense than Pv modes, indicating strong polarizability of the bonds in PPv. The observed Raman mode frequency range of PPv extends to much higher frequencies than Pv, which can be related to the edge sharing of the GeO6 octahedra in PPv which would make Ge-O bonds stronger. The spectroscopic Gr{\"u}neisen parameters of Pv and PPv are constrained to be 1.56 ± 0.10 and 1.15 ± 0.06, respectively, at the PPv transition. We also estimated that the thermal expansion parameter decreases by 25 ± 10{\%} across the PPv transition. If a similar change occurs in MgSiO3, the low thermal expansivity would dynamically stabilize the PPv layer at the lowermost mantle. Using our Raman measurements and a Kieffer-type model, the Clapeyron slope of the PPv transition is constrained to be + 20 ± 10 MPa/K. The strong positive slope is consistent with the prediction for MgSiO3 and is related to a positive shift of phonon density of states at high-frequency region resulting from the formation of the edge sharing among the GeO6 (or SiO6) octahedra in PPv.",
keywords = "Clapeyron slope, Gr{\"u}neisen parameter, perovskite, post-perovskite, Raman spectroscopy, thermal expansivity",
author = "Sang-Heon Shim and Atsushi Kubo and Duffy, {Thomas S.}",
year = "2007",
month = "8",
day = "15",
doi = "10.1016/j.epsl.2007.05.027",
language = "English (US)",
volume = "260",
pages = "166--178",
journal = "Earth and Planetary Sciences Letters",
issn = "0012-821X",
publisher = "Elsevier",
number = "1-2",

}

TY - JOUR

T1 - Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa

AU - Shim, Sang-Heon

AU - Kubo, Atsushi

AU - Duffy, Thomas S.

PY - 2007/8/15

Y1 - 2007/8/15

N2 - Raman spectra of the perovskite (Pv) and post-perovskite (PPv) phases of MgGeO3 were measured in the laser-heated diamond cell up to 123 GPa. Between 14 and 51 GPa we observed a total of seven Pv modes, the frequencies and relative intensities of which are similar to MgSiO3-Pv with systematically lower frequencies. We also observe a total of ten PPv modes which are much more intense than Pv modes, indicating strong polarizability of the bonds in PPv. The observed Raman mode frequency range of PPv extends to much higher frequencies than Pv, which can be related to the edge sharing of the GeO6 octahedra in PPv which would make Ge-O bonds stronger. The spectroscopic Grüneisen parameters of Pv and PPv are constrained to be 1.56 ± 0.10 and 1.15 ± 0.06, respectively, at the PPv transition. We also estimated that the thermal expansion parameter decreases by 25 ± 10% across the PPv transition. If a similar change occurs in MgSiO3, the low thermal expansivity would dynamically stabilize the PPv layer at the lowermost mantle. Using our Raman measurements and a Kieffer-type model, the Clapeyron slope of the PPv transition is constrained to be + 20 ± 10 MPa/K. The strong positive slope is consistent with the prediction for MgSiO3 and is related to a positive shift of phonon density of states at high-frequency region resulting from the formation of the edge sharing among the GeO6 (or SiO6) octahedra in PPv.

AB - Raman spectra of the perovskite (Pv) and post-perovskite (PPv) phases of MgGeO3 were measured in the laser-heated diamond cell up to 123 GPa. Between 14 and 51 GPa we observed a total of seven Pv modes, the frequencies and relative intensities of which are similar to MgSiO3-Pv with systematically lower frequencies. We also observe a total of ten PPv modes which are much more intense than Pv modes, indicating strong polarizability of the bonds in PPv. The observed Raman mode frequency range of PPv extends to much higher frequencies than Pv, which can be related to the edge sharing of the GeO6 octahedra in PPv which would make Ge-O bonds stronger. The spectroscopic Grüneisen parameters of Pv and PPv are constrained to be 1.56 ± 0.10 and 1.15 ± 0.06, respectively, at the PPv transition. We also estimated that the thermal expansion parameter decreases by 25 ± 10% across the PPv transition. If a similar change occurs in MgSiO3, the low thermal expansivity would dynamically stabilize the PPv layer at the lowermost mantle. Using our Raman measurements and a Kieffer-type model, the Clapeyron slope of the PPv transition is constrained to be + 20 ± 10 MPa/K. The strong positive slope is consistent with the prediction for MgSiO3 and is related to a positive shift of phonon density of states at high-frequency region resulting from the formation of the edge sharing among the GeO6 (or SiO6) octahedra in PPv.

KW - Clapeyron slope

KW - Grüneisen parameter

KW - perovskite

KW - post-perovskite

KW - Raman spectroscopy

KW - thermal expansivity

UR - http://www.scopus.com/inward/record.url?scp=34447264764&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34447264764&partnerID=8YFLogxK

U2 - 10.1016/j.epsl.2007.05.027

DO - 10.1016/j.epsl.2007.05.027

M3 - Article

VL - 260

SP - 166

EP - 178

JO - Earth and Planetary Sciences Letters

JF - Earth and Planetary Sciences Letters

SN - 0012-821X

IS - 1-2

ER -