Modeling defects and plasticity in MgSiO3 post-perovskite: Part 3—Screw and edge [001] dislocations

Goryaeva, Alexandra M.; Carrez, Philippe

doi:10.1007/s00269-017-0879-0

Cited by 12 publications

(11 citation statements)

References 53 publications

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“…Not surprisingly, this shear is very easy to produce along the magnesium layer in the (010) plane 19 , 20 . The second easiest slip system also corresponds to shear in (010) but along the [001] direction 21 . Shear along [010] raises some questions, because it would require activating dislocations with a very large Burgers vector.…”

Section: Resultsmentioning

confidence: 99%

“…In this study we focus on intracrystalline mechanisms. Owing to the very peculiar crystal structure of post-perovskite, dislocation glide appears easy only in the plane of structural layering 19 – 21 . However, which deformation mechanism effectively accounts for strain components out of the (010) plane remains an open question which is fundamental to address in order to model CPO fabrics and the resulting seismic properties.…”

Section: Discussionmentioning

confidence: 99%

“…Finally, the twinning stress, computed here at 0 K and supposed to be mostly athermal 30 , can be compared to the lattice friction of dislocation glide in post-perovskite materials 20 , 21 , 24 . In CaIrO 3 , the twinning stress reported here is at least 30% below any lattice friction level 24 .…”

Section: Discussionmentioning

confidence: 99%

“…Given the formidable difficulties of deformation experiments under very high pressures, numerical modelling currently represents a very attractive alternative. Using atomic-scale modelling of dislocations 19 – 21 , we have shown that shearing the post-perovskite structure occurs easily along the shortest [100] lattice repeat in the Mg-O layer (010) plane, with a lattice friction of 2 GPa 20 . The other dense direction in this plane, [001], is the second easiest 21 (ca.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of Mechanical Twinning in Magnesium Silicate Post-Perovskite

Carrez

Goryaeva

2017

Sci Rep

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The plastic properties of MgSiO3 post-perovskite are considered to be one of the key issues necessary for understanding the seismic anisotropy at the bottom of the mantle in the so-called D” layer. Although plastic slip in MgSiO3 post-perovskite has attracted considerable attention, the twinning mechanism has not been addressed, despite some experimental evidence from low-pressure analogues. On the basis of a numerical mechanical model, we present a twin nucleation model for post-perovskite involving the emission of 1/6 <110> partial dislocations. Relying on first-principles calculations with no adjustable parameters, we show that {110} twin wall formation resulting from the interaction of multiple twin dislocations occurs at a twinning stress comparable in magnitude to the most readily occurring slip system in post-perovskite. Because dislocation activities and twinning are competitive strain-producing mechanisms, twinning should be considered in future models of crystallographic preferred orientations in post-perovskite to better interpret seismic anisotropy in the lowermost lower mantle.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of Mechanical Twinning in Magnesium Silicate Post-Perovskite

Carrez

Goryaeva

2017

Sci Rep

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“…We determined a representative elastic tensor for Ppv texture development in high-strain simple shear by querying the TX2008.V1.P010 model of Walker et al (2011), which combined a lower mantle viscosity model from Mitrovica and Forte (2004) with a mantle density model from Simmons et al (2009). We only considered the case in which slip on the (010) plane dominates; this is the most likely slip plane for Ppv based on experiments (Walte et al, 10 2009;Yamazaki et al, 2006), modeling (Goryaeva et al, 2017), and observations of D"…”

Section: Candidate Models For D" Anisotropymentioning

confidence: 99%