eprintid: 142081
rev_number: 49
eprint_status: archive
userid: 608
dir: disk0/00/14/20/81
datestamp: 2010-10-27 08:11:34
lastmod: 2021-10-23 23:00:19
status_changed: 2012-09-26 15:48:28
type: article
metadata_visibility: show
item_issues_count: 0
creators_name: Karki, BB
creators_name: Stixrude, L
creators_name: Wentzcovitch, RM
title: High-pressure elastic properties of major materials of Earth's mantle from first principles
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F57
keywords: Generalized-gradient approximation, Orthorhombic MgSiO3 perovskite, Total-energy calculations, Seismic-wave attenuation, Induced breathing model, Hcp transition-metals, X-ray-diffraction, Ab-initio, Molecular-dynamics, Phase-transitions
note: Copyright 2001 by the American Geophysical Union
abstract: The elasticity of materials is important for our understanding of processes ranging from brittle failure, to flexure, to the propagation of elastic waves. Seismologically revealed structure of the Earth's mantle, including the radial (one-dimensional) profile, lateral heterogeneity, and anisotropy are determined largely by the elasticity of the materials that make up this region. Despite its importance to geophysics, our knowledge of the elasticity of potentially relevant mineral phases at conditions typical of the Earth's mantle is still limited: Measuring the elastic constants at elevated pressure-temperature conditions in the laboratory remains a major challenge. Over the past several years, another approach has been developed based on first-principles quantum mechanical theory. First-principles calculations provide the ideal complement to the laboratory approach because they require no input from experiment; that is, there are no free parameters in the theory. Such calculations have true predictive power and can supply critical information including that which is difficult to measure experimentally. A review of high-pressure theoretical studies of major mantle phases shows a wide diversity of elastic behavior among important tetrahedrally and octahedrally coordinated Mg and Ca silicates and Mg, Ca, Al, and Si oxides. This is particularly apparent in the acoustic anisotropy, which is essential for understanding the relationship between seismically observed anisotropy and mantle flow. The acoustic anisotropy of the phases studied varies from zero to more than 50% and is found to depend on pressure strongly, and in some cases nonmonotonically. For example, the anisotropy in MgO decreases with pressure up to 15 GPa before increasing upon further compression, reaching 50% at a pressure of 130 GPa. Compression also has a strong effect on the elasticity through pressure-induced phase transitions in several systems. For example, the transition from stishovite to CaCl2 structure in silica is accompanied by a discontinuous change in the shear (S) wave velocity that is so large (60%) that it may be observable seismologically. Unifying patterns emerge as well: Eulerian finite strain theory is found to provide a good description of the pressure dependence of the elastic constants for most phases. This is in contrast to an evaluation of Birch's law, which shows that this systematic accounts only roughly for the effect of pressure, composition, and structure on the longitudinal (P) wave velocity. The growing body of theoretical work now allows a detailed comparison with seismological observations. The athermal elastic wave velocities of most important mantle phases are found to be higher than the seismic wave velocities of the mantle by amounts that are consistent with the anticipated effects of temperature and iron content on the P and S wave velocities of the phases studied. An examination of future directions focuses on strategies for extending first-principles studies to more challenging but geophysically relevant situations such as solid solutions, high-temperature conditions, and mineral composites.
date: 2001-11
publisher: AMER GEOPHYSICAL UNION
official_url: http://dx.doi.org/10.1029/2000RG000088
vfaculties: VMPS
oa_status: green
language: eng
primo: open
primo_central: open_green
article_type_text: Review
verified: verified_batch
elements_source: Web of Science
elements_id: 225490
doi: 10.1029/2000RG000088
language_elements: EN
lyricists_name: Stixrude, Lars
lyricists_id: LSTIX78
full_text_status: public
publication: Reviews of Geophysics
volume: 39
number: 4
pagerange: 507 - 534
issn: 8755-1209
citation:        Karki, BB;    Stixrude, L;    Wentzcovitch, RM;      (2001)    High-pressure elastic properties of major materials of Earth's mantle from first principles.                   Reviews of Geophysics , 39  (4)   507 - 534.    10.1029/2000RG000088 <https://doi.org/10.1029/2000RG000088>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/142081/1/2000RG000088.pdf