Journal ArticleDOI
Ab initio structural and thermoelastic properties of orthorhombic MgSiO3 perovskite
George Wolf,M. S. T. Bukowinski +1 more
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In this article, the structural and thermoelastic properties of orthorhombic (Pbnm) MgSiO3 perovskite as a function of temperature and pressure were investigated.Abstract:
We present results of an ab initio study of the structural and thermoelastic properties of orthorhombic (Pbnm) MgSiO3 perovskite as a function of temperature and pressure. Self-consistent free energies are computed using quasiharmonic lattice dynamics with interatomic potentials derived from an electron-gas formulation. At high temperatures the orthorhombic phase undergoes successive second-order transitions to tetragonal and cubic phases. The transition temperatures increase with pressure such that the orthorhombic phase is stable throughout most of the lower mantle although the higher symmetry phases could occur near the top of the lower mantle. At zero pressure the calculated bulk modulus and thermal expansion are in excellent agreement with the available data. We find that for high-temperature isotherms, a finite-strain decompression of the high-pressure equation of state of perovskite substantially overestimates its zero-pressure density and bulk modulus; hence, constraints on the chemical composition of the lower mantle, based on a comparison of the decompressed seismological properties with zero-pressure laboratory data may significantly overestimate the proportion of perovskite in the lower mantle.read more
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Composition of the upper mantle: Geophysical tests of two petrological models
Jay D. Bass,Don L. Anderson +1 more
TL;DR: In this paper, the elastic properties of candidate mantle phases are used to test the viability of olivine-rich (pyrolitic) and CaO + Al_2O_3-rich assemblages for the mantle.
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Mantle layering from ScS reverberations: 2. The transition zone
TL;DR: In this article, the authors examined the nature of mantle layering using the ScSn phases and internal reflections observed within the reverberative interval of SH-polarized seismograms and derived path-specific estimates of the travel times to the 410-km and 660-km discontinuities and their reflection coefficients.
Journal ArticleDOI
Static compression of iron to 78 GPa with rare gas solids as pressure-transmitting media
TL;DR: In this article, the room temperature, static compression of iron to 78 GPa with solid neon and argon as pressure-transmitting media was performed in a diamond anvil cell.
Journal ArticleDOI
Thermal expansion of silicate perovskite and stratification of the Earth's mantle
TL;DR: The thermal expansion coefficient of perovskite provides an important constraint on possible compositional models for the lower mantle as discussed by the authors, which suggests that the upper and lower mantle are chemically distinct.
References
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Journal ArticleDOI
The Elastic Behaviour of a Crystalline Aggregate
TL;DR: The connection between the elastic behavior of an aggregate and a single crystal is considered in this article, with special reference to the theories of Voigt, Reuss, and Huber and Schmid.
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A variational approach to the theory of the elastic behaviour of multiphase materials
Zvi Hashin,S. Shtrikman +1 more
TL;DR: In this paper, the authors derived upper and lower bounds for the effective elastic moduli of quasi-isotropic and quasi-homogeneous multiphase materials of arbitrary phase geometry.
Journal ArticleDOI
Finite Elastic Strain of Cubic Crystals
TL;DR: In this article, Murnaghan's theory of finite strain is developed for a medium of cubic symmetry subjected to finite hydrostatic compression, plus an arbitrary homogeneous infinitesimal strain.
Journal ArticleDOI
Calibration of the ruby pressure gauge to 800 kbar under quasi-hydrostatic conditions
TL;DR: An improved calibration curve of the pressure shift of the ruby R1 emission line was obtained under quasi-hydrostatic conditions in the diamond-window, high-pressure cell to 800 kbar.
Journal ArticleDOI
A simplified method for calculating the debye temperature from elastic constants
TL;DR: In this article, it was shown that the Reuss and Voigt approximations can be used to estimate, accurately, the mean sound velocity of a crystal, which is proportioned to the Debye temperature.
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