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Equation of state of NaMgF 3 postperovskite: Implication for the seismic velocity changes in the D″ region
Author(s) -
Hustoft Justin,
Catalli Krystle,
Shim SangHeon,
Kubo Atsushi,
Prakapenka Vitali B.,
Kunz Martin
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl034042
Subject(s) - discontinuity (linguistics) , hydrostatic equilibrium , perovskite (structure) , condensed matter physics , materials science , p wave , mineralogy , physics , geology , chemistry , crystallography , mathematics , medicine , mathematical analysis , quantum mechanics , cardiology , atrial fibrillation
Recent first‐principles calculations have proposed that bulk sound speed ( V Φ ) decreases at the perovskite (Pv) → postperovskite (PPv) transition. Yet some measurements suggest an increase in V Φ at the PPv transition in (Mg,Fe)SiO 3 and NaMgF 3 . Our new measurements on NaMgF 3 up to 50 GPa under quasi‐hydrostatic stress conditions reveal that the V Φ of PPv remains lower than that of Pv near the PPv transition, consistent with a first‐principles study on NaMgF 3 . Combined with similar observations in (Mg,Fe)SiO 3 , MgGeO 3 , and CaIrO 3 , our result on NaMgF 3 suggests that the V Φ 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 the anticorrelation between the V Φ and S ‐wave velocity anomalies in the D″ region.