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Effect of Al on the sharpness of the MgSiO3 perovskite to post-perovskite phase transition
 

Summary: Effect of Al on the sharpness of the MgSiO3 perovskite to
post-perovskite phase transition
S. Akber-Knutson,1
G. Steinle-Neumann,2
and P. D. Asimow1
Received 8 April 2005; revised 8 June 2005; accepted 13 June 2005; published 19 July 2005.
[1] By means of static ab-initio computations we investigate
the influence of Al on the recently discovered perovskite to
post-perovskite phase transition in MgSiO3. We examine
three substitution mechanisms for Al in the two structures:
MgSi ! AlAl; SiSiO ! AlAl5; and Si ! AlH. The
substitutions introducing oxygen vacancies (highly
unfavorable, energetically) and water (favorable) both
lower the 0 Kelvin transition pressure, whereas charge
coupled substitution increases it relative to 105 GPa for
pure MgSiO3. From the transition pressures for 0, 6.25,
and 100 mol% charge coupled Al2O3 incorporation
and simple solution theories, we estimate the phase diagram
of Al-bearing MgSiO3 at low Al concentrations. Assuming
the Clapeyron slope is independent of Al concentration, we

  

Source: Asimow, Paul D. - Division of Geological and Planetary Sciences, California Institute of Technology,
Steinle-Neumann, Gerd - Bayerisches Geoinstitut, Universitšt Bayreuth

 

Collections: Geosciences