Equation of state of NaMgF[subscript 3] postperovskite: Implication for the seismic velocity changes in the D" region
- 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:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006645
- Journal Information:
- Geophys. Res. Lett., Vol. 35, Issue 2008; ISSN 0094-8276
- Country of Publication:
- United States
- Language:
- ENGLISH
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