First principles investigation of the postspinel transition in Mg2SiO4

Yonggang G. Yu; Renata M. Wentzcovitch; Taku Tsuchiya; Koichiro Umemoto; Donald J. Weidner

doi:10.1029/2007GL029462

First principles investigation of the postspinel transition in Mg₂SiO₄

Yonggang G. Yu, Renata M. Wentzcovitch, Taku Tsuchiya, Koichiro Umemoto, Donald J. Weidner

Chemical Engineering and Materials Science

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Abstract

We have investigated the dissociation of iron free ringwoodite, Mg₂SiO₄ γ-spinel, into MgO periclase and MgSiO₃ perovskite using quasi-harmonic free energy computations within the local density approximation (LDA) and generalized gradient approximation (GGA). The transition pressure, P_tr, obtained from GGA is higher and in much better agreement with experimental measurements than its LDA counterpart. This can be rationalized by close inspection of GGA and LDA functional forms. The Clapeyron slope obtained from this calculation is -2.9 - -2.6 MPa/K. Surprisingly, we find a small decrease in bulk sound velocity across this transition. Our results are consistent with 64 ± 12% ringwoodite volume fraction at the bottom of the transition zone.

Original language	English (US)
Article number	L10306
Journal	Geophysical Research Letters
Volume	34
Issue number	10
DOIs	https://doi.org/10.1029/2007GL029462
State	Published - May 28 2007

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title = "First principles investigation of the postspinel transition in Mg2SiO4",

abstract = "We have investigated the dissociation of iron free ringwoodite, Mg2SiO4 γ-spinel, into MgO periclase and MgSiO3 perovskite using quasi-harmonic free energy computations within the local density approximation (LDA) and generalized gradient approximation (GGA). The transition pressure, Ptr, obtained from GGA is higher and in much better agreement with experimental measurements than its LDA counterpart. This can be rationalized by close inspection of GGA and LDA functional forms. The Clapeyron slope obtained from this calculation is -2.9 - -2.6 MPa/K. Surprisingly, we find a small decrease in bulk sound velocity across this transition. Our results are consistent with 64 ± 12% ringwoodite volume fraction at the bottom of the transition zone.",

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AU - Yu, Yonggang G.

AU - Wentzcovitch, Renata M.

AU - Tsuchiya, Taku

AU - Umemoto, Koichiro

AU - Weidner, Donald J.

PY - 2007/5/28

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AB - We have investigated the dissociation of iron free ringwoodite, Mg2SiO4 γ-spinel, into MgO periclase and MgSiO3 perovskite using quasi-harmonic free energy computations within the local density approximation (LDA) and generalized gradient approximation (GGA). The transition pressure, Ptr, obtained from GGA is higher and in much better agreement with experimental measurements than its LDA counterpart. This can be rationalized by close inspection of GGA and LDA functional forms. The Clapeyron slope obtained from this calculation is -2.9 - -2.6 MPa/K. Surprisingly, we find a small decrease in bulk sound velocity across this transition. Our results are consistent with 64 ± 12% ringwoodite volume fraction at the bottom of the transition zone.

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First principles investigation of the postspinel transition in Mg₂SiO₄

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