The equations of state of forsterite, wadsleyite, ringwoodite, akimotoite, MgSiO3-perovskite, and postperovskite and phase diagram for the Mg2SiO4 system at pressures of up to 130 GPa

Abstract

The equations of state of forsterite, wadsleyite, ringwoodite, MgSiO3-perovskite, akimotoite, and postperovskite are set up by joint analysis of experimentally measured isobaric heat capacity, bulk moduli, thermal expansion depending on temperature at ambient pressure, and volume at room and higher temperatures. Modified equations of state based on the Helmholtz free energy are used to construct a thermodynamic model. The derived equations of state permit calculation of all thermodynamic functions for the minerals depending on temperature and volume or temperature and pressure. A phase diagram of the system MgSiO3–MgO is constructed based on the Gibbs energy calibrated using the referred experimental points. The seismic boundaries at depths of 410 and 520 km and in the zone D’ are interpreted on the basis of the phase transitions. The global upper/lower mantle discontinuity at a depth of 660 km remains debatable; it is in poor agreement with experimental and computational data on the dissociation of ringwoodite to perovskite and periclase.

Intercomparison of the gold, platinum, and MgO pressure scales up to 140 GPa and 2500 K

“…Our data show that the Au‐Y09 and Pt‐Y09 scales agree well with each other. However, similar to the scales by Dorogokupets et al [], they show systematic differences with the MgO‐T09 scale (Figure c).…”

“…(a, c, and e) Grüneisen parameters, γ 2000K , and (b, d, and f) thermal pressures, P tot ( V ,2000K) − P st ( V ,300K) (=Δ P th ( V ,2000K) + Δ P el ( V ,2000K)) in equation , of MgO, platinum, and gold at 2000 K and high pressure. Solid curves: Dorogokupets and Dewaele [], dotted curves: Dorogokupets et al [], dashed dot curves: Tange et al [] for MgO and Yokoo et al [] for Pt and Au, and dashed curves: Speziale et al [] for MgO and Fei et al [] for Au and Pt.…”

“…We also calculate pressure differences between 2000 and 300 K isotherms for given volumes, i.e., pressure contributions from nonstatic terms, P tot ( V ,2000K) − P st ( V ,300K), in equation , including the thermal (Δ P th ( V ,2000K)) and electronic (Δ P el ( V ,2000K)) effects which are temperature sensitive. The scales by Dorogokupets and Dewaele [] and Dorogokupets et al [] include both the anharmonic effects (Au, Pt, and MgO) and the electronic effects (Au and Pt). The scales by Yokoo et al [] and Tange et al [] include the electronic effects for Au and Pt, but not the anharmonic effects.…”

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K

“…In this work, we propose updated EoSs for Fe phases based on a formalism from our recent publications2930313233343536. In addition, the magnetic contribution to the Helmholtz free energy was calculated according to ref.…”

Thermoelastic properties of chromium oxide Cr2O3 (eskolaite) at high pressures and temperatures

“…The dataset is used for thermodynamic calculation on rocks, melts and aqueous fluids under crustal to deep mantle conditions. The better thermodynamic characterization of each end-member including in the dataset, therefore, considerably enhances the capabilities of this calculation (e.g., Dorogokupets et al 2015). Revised data on the thermal expansion and compressibility of Esk obtained in this paper contributes to this deal.…”