Premium
First principles investigation of the postspinel transition in Mg 2 SiO 4
Author(s) -
Yu Yonggang G.,
Wentzcovitch Renata M.,
Tsuchiya Taku,
Umemoto Koichiro,
Weidner Donald J.
Publication year - 2007
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 - 10.1029/2007gl029462
Subject(s) - ringwoodite , periclase , spinel , stishovite , transition zone , materials science , local density approximation , thermodynamics , mineralogy , condensed matter physics , physics , chemistry , high pressure , electronic structure , metallurgy , geophysics
We have investigated the dissociation of iron free ringwoodite, Mg 2 SiO 4 γ ‐spinel, into MgO periclase and MgSiO 3 perovskite using quasi‐harmonic free energy computations within the local density approximation (LDA) and generalized gradient approximation (GGA). The transition pressure, P tr , obtained from GGA is higher and in much better agreement with experimental measurements than its LDA counterpart. This can be rationalized by close inspection of GGA and LDA functional forms. The Clapeyron slope obtained from this calculation is −2.9 − −2.6 MPa/K. Surprisingly, we find a small decrease in bulk sound velocity across this transition. Our results are consistent with 64 ± 12% ringwoodite volume fraction at the bottom of the transition zone.