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<datestamp>2018-01-11</datestamp>
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<title lang=en>Predicted glide systems and crystal preferred orientations of polycrystalline silicate Mg-Perovskite at high pressure: Implications for the seismic anisotropy in the lower mantle</title>
<creator>Mainprice, Dave</creator>
<creator>Tommasi, Andrea</creator>
<creator>Ferre, D.</creator>
<creator>Carrez, P.</creator>
<creator>Cordier, P.</creator>
<contributor>Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Laboratoire de structures et propriétés de l'état solide (LSPES) ; Université de Lille, Sciences et Technologies - Centre National de la Recherche Scientifique (CNRS)</contributor>
<description>International audience</description>
<source>ISSN: 0012-821X</source>
<source>Earth and Planetary Science Letters</source>
<publisher>Elsevier</publisher>
<identifier>hal-00411460</identifier>
<identifier>https://hal.archives-ouvertes.fr/hal-00411460</identifier>
<source>https://hal.archives-ouvertes.fr/hal-00411460</source>
<source>Earth and Planetary Science Letters, Elsevier, 2008, 271 (1-4), pp.135-144. 〈10.1016/j.epsl.2008.03.058〉</source>
<identifier>DOI : 10.1016/j.epsl.2008.03.058</identifier>
<relation>info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2008.03.058</relation>
<language>en</language>
<subject lang=en>perovskite</subject>
<subject lang=en>ab initio</subject>
<subject lang=en>dislocation creep</subject>
<subject lang=en>glide systems</subject>
<subject lang=en>crystal preferred orientation</subject>
<subject lang=en>seismic anisotropy</subject>
<subject lang=en>lower mantle</subject>
<subject>[SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography</subject>
<type>info:eu-repo/semantics/article</type>
<type>Journal articles</type>
<description lang=en>We use first first-principle methods and the Peierls-Nabarro model to evaluate the resistance to glide, characterized by the Peierls stress, of glide systems for end-member MgSiO3 Perovskite at mantle pressures. [010](100) is the easiest glide system in Mg-Perovskite at all pressures. Peierls stresses increase systematically with pressure for all systems except [001](010), indicating the importance of lattice friction at lower mantle pressures. The ratio of the maximum Peierls stress for each system relative to the [010](100) value defines their critical resolved shear stress (CRSS). These CRSS are used in a visco-plastic self-consistent homogenization model to predict the evolution of crystal preferred orientations (CPO) during deformation of polycrystalline Mg-Perovskite. In axial compression, [100] tends to align with the compression direction, in agreement with in situ observations in axial compression experiments. In simple shear, [010] concentrates near the shear direction and (100), although more dispersed, tends to align near the shear plane, consistent with the dominant activity of the easier [010](100) system. The calculated seismic anisotropy for a 100% Mg-Perovskite aggregate using the CPO in simple shear and the elastic constants Of MgSiO3 perovskite at lower mantle pressures and temperatures is weak (>3% for P-waves with and >2% for S-waves) and decreases with increasing temperature and pressure. P-waves show the fastest propagation parallel to the lineation and S-waves fast polarization is in the foliation at 38 GPa and normal to the lineation at 88 GPa. This weak anisotropy is consistent with global seismological observations of a nearly isotropic lower mantle. There are however two regions where strain-induced Mg-Perovskite CPO could contribute to anisotropy; a) low temperature regions in the uppermost lower mantle, where the predicted S-wave polarization anisotropy may attain 1.6% with a fast polarization parallel to the foliation, b) in high high-temperature domains in the D '' layer, where Mg-Perovskite may be the major stable phase, leading to polarization of fast S-waves normal to the lineation for propagation directions at high angle to the lineation and an apparent isotropy for all other propagation directions.</description>
<date>2008</date>
</dc>
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