Open AccessFirst principles study of thermodynamics and phase transition in low‐pressure (P2 1 /c) and high‐pressure (C2/c) clinoenstatite MgSiO 3
Author(s) -
Yu Yonggang G.,
Wentzcovitch Renata M.,
Angel Ross J.
Publication year - 2010
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jb006329
Subject(s) - thermodynamics , triple point , pyroxene , phase transition , equation of state , phase (matter) , materials science , high pressure , physics , chemistry , mineralogy , olivine , quantum mechanics
Using first principles quasi‐harmonic theory, we have investigated the vibrational and thermodynamic properties of P2 1 /c and C2/c MgSiO 3 clinoenstatites. Very good agreement between experimentally measured thermodynamic properties, such as equation of state, and those predicted by the local density approximation (LDA) functional has been found. The level of agreement found in these chain silicates is comparable to that found in framework silicates such as MgSiO 3 perovskite. The phase boundaries calculated by the LDA and the generalized gradient approximation (GGA) bracket the experimentally measured ones following the established trend that the GGA functional overestimates the transition pressure while the LDA functional underestimates it. The calculated Clapeyron slope is 2.9 MPa K −1 and is used to constrain the position of the 3‐pyroxene (P2 1 /c, C2/c, and Pbca) triple point in MgSiO 3 , with the aid of room temperature experimental hysteresis in the P2 1 /c to C2/c transition.