NaMgF3: A low-pressure analog of MgSiO3

K. Umemoto, R. M. Wentzcovitch, D. J. Weidner, J. B. Parise

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Abstract

Using first principles computations we show that NaMgF3 perovskite undergoes the same series of phase transitions as MgSiO3 perovskite, that is, the postperovskite transition and the dissociation into CsCl-type NaF and cotunnite-type MgF2. These fluorides also undergo the same series of phase transitions as MgO and SiO2, the dissociation products of MgSiO3. Since the phase transformations in NaMgF3 are not accompanied by any soft mode, we compute quasi-harmonic free energies and the respective phase boundaries. They have positive and negative Clapeyron slopes, respectively, like MgSiO3. However, the transition pressures in NaMgF3 are much lower and could be easily achieved in diamond anvil experiments. Therefore NaMgF3 should be a good low-pressure analog of MgSiO3.

Original languageEnglish (US)
Article numberL15304
JournalGeophysical Research Letters
Volume33
Issue number15
DOIs
StatePublished - Aug 2006

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