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Phase transition in MgSiO3 perovskite in the earth’s lower mantle
A new polymorph of MgSiO3 more stable than the Pbnm-perovskite phase has been identified by first-principles computations. It has the CaIrO3 structure with Cmcm symmetry and consists of SiO3 layers… Expand
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Spin states and hyperfine interactions of iron in (Mg,Fe)SiO$_{3}$ perovskite under pressure
- P. Blaha, H. Hsu, K. Umemoto, R. Wentzcovitch
- Materials Science, Geology
- 17 March 2010
Abstract With the guidance of first-principles phonon calculations, we have searched and found several metastable equilibrium sites for substitutional ferrous iron in MgSiO 3 perovskite. In the… Expand
Phase transition in MgSiO 3 perovskite in the earth's lower mantle
- T. Tsuchiya, J. Tsuchiya, K. Umemoto, R. Wentzcovitch
- Geology
- 15 August 2004
A new polymorph of MgSiO3 more stable than the Pbnm-perovskite phase has been identified by first-principles computations. It has the CaIrO3 structure with Cmcm symmetry and consists of SiO3 layers… Expand
Dissociation of MgSiO3 in the Cores of Gas Giants and Terrestrial Exoplanets
- K. Umemoto, R. Wentzcovitch, P. B. Allen
- Chemistry, Medicine
- Science
- 17 February 2006
CaIrO3-type MgSiO3 is the planet-forming silicate stable at pressures and temperatures beyond those of Earth's core-mantle boundary. First-principles quasiharmonic free-energy computations show that… Expand
Elasticity of post‐perovskite MgSiO3
- T. Tsuchiya, J. Tsuchiya, K. Umemoto, R. Wentzcovitch
- Materials Science
- 1 July 2004
[1] We have determined by first principles the athermal elastic constant tensor, single crystal and aggregated acoustic velocities, and anisotropy of the recently discovered post-perovskite MgSiO3… Expand
Pressure-volume-temperature relations in MgO: An ultrahigh pressure-temperature scale for planetary sciences applications
- Z. Wu, R. Wentzcovitch, K. Umemoto, B. Li, K. Hirose, Jin-Cheng Zheng
- Materials Science
- 1 June 2008
[1] In situ crystallography based on diamond anvil cells have been extended to the multimegabar regime. Temperatures in these experiments have crossed the 2500 K mark. Yet, current high… Expand
First principles investigation of the postspinel transition in Mg2SiO4
- Y. G. Yu, R. Wentzcovitch, T. Tsuchiya, K. Umemoto, D. Weidner
- Materials Science
- 1 May 2007
[1] We have investigated the dissociation of iron free ringwoodite, Mg2SiO4γ-spinel, into MgO periclase and MgSiO3 perovskite using quasi-harmonic free energy computations within the local density… Expand
first-principles investigation of hydrous defects and IR frequencies in forsterite: The case for Si vacancies
- K. Umemoto, R. Wentzcovitch, M. Hirschmann, D. Kohlstedt, A. C. Withers
- Materials Science
- 23 March 2011
Abstract We investigate charge-balanced hydrous magnesium and silicon defects [(2H)XMg, (4H)XSi] by first principles. Two new lowest-energy hydrogen configurations are proposed for (4H)XSi. With… Expand
Two-stage dissociation in MgSiO3 post-perovskite
- K. Umemoto, R. Wentzcovitch
- Geology
- 15 November 2011
Abstract The fate of MgSiO 3 post-perovskite under TPa pressures is key information for understanding and modeling interiors of super-Earths-type exoplanets and solar giants' cores. Here, we report a… Expand
NaMgF3: a low-pressure analog of MgSiO3
- K. Umemoto, R. Wentzcovitch, D. Weidner, J. Parise
- Materials Science
- 1 August 2006
[1] Using first principles computations we show that NaMgF 3 perovskite undergoes the same series of phase transitions as MgSiO 3 perovskite, that is, the post-perovskite transition and the… Expand
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