Equation of state of NaMgF[subscript 3] postperovskite: Implication for the seismic velocity changes in the D" region

Journal Article · Wed Jul 02 04:00:00 EDT 2008 · Geophys. Res. Lett.

DOI:https://doi.org/10.1029/2008GL034042· OSTI ID:1006645

Hustoft, J; Catalli, K; Shim, S -H; Kubo, A; Prakapenka, V B; Kunz, M ^[1]

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1. MIT

Recent first-principles calculations have proposed that bulk sound speed (V{sub {phi}}) decreases at the perovskite (Pv) {yields} postperovskite (PPv) transition. Yet some measurements suggest an increase in V{sub {phi}} at the PPv transition in (Mg,Fe)SiO{sub 3} and NaMgF{sub 3}. Our new measurements on NaMgF{sub 3} up to 50 GPa under quasi-hydrostatic stress conditions reveal that the V{sub {phi}} of PPv remains lower than that of Pv near the PPv transition, consistent with a first-principles study on NaMgF{sub 3}. Combined with similar observations in (Mg,Fe)SiO{sub 3}, MgGeO{sub 3}, and CaIrO{sub 3}, our result on NaMgF{sub 3} suggests that the V{sub {phi}} decrease is a robust trend in the PPv transition and is controlled more by crystal structure than by chemical composition. Our finding also strengthens the proposal that the elastic properties of PPv can explain the small P-wave increase across the D'' discontinuity and th anticorrelation between the V{sub {phi}} and S-wave velocity anomalies in the D'' region.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1006645
• Journal Information: Geophys. Res. Lett., Journal Name: Geophys. Res. Lett. Journal Issue: 2008 Vol. 35; ISSN GPRLAJ; ISSN 0094-8276
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

58 GEOSCIENCES
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
ELASTICITY
EQUATIONS OF STATE
PEROVSKITE
SOUND WAVES
VELOCITY
YIELDS