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Modeling defects and plasticity in MgSiO3 post-perovskite: Part 2-screw and edge [100] dislocations.

Goryaeva AM, Carrez P, Cordier P - Phys Chem Miner (2015)

Bottom Line: We show that despite a small tendency to core spreading in {011}, [100] screw dislocations glide very easily (Peierls stress of 1 GPa) in (010) where only Mg-O bonds are to be sheared.Whatever the planes, (010), (001) or {011}, edge dislocations are characterized by a wider core (of the order of 2b).The layered structure of post-perovskite results in a drastic reduction in lattice friction opposed to the easiest slip systems compared to perovskite.

View Article: PubMed Central - PubMed

Affiliation: Unité Matériaux et Transformations, UMR CNRS 8207, Université de Lille1, Bat C6, 59655 Villeneuve d'Ascq Cedex, France.

ABSTRACT

In this study, we propose a full atomistic study of [100] dislocations in MgSiO3 post-perovskite based on the pairwise potential parameterized by Oganov et al. (Phys Earth Planet Inter 122:277-288, 2000) for MgSiO3 perovskite. We model screw dislocations to identify planes where they glide easier. We show that despite a small tendency to core spreading in {011}, [100] screw dislocations glide very easily (Peierls stress of 1 GPa) in (010) where only Mg-O bonds are to be sheared. Crossing the Si-layers results in a higher lattice friction as shown by the Peierls stress of [100](001): 17.5 GPa. Glide of [100] screw dislocations in {011} appears also to be highly unfavorable. Whatever the planes, (010), (001) or {011}, edge dislocations are characterized by a wider core (of the order of 2b). Contrary to screw character, they bear negligible lattice friction (0.1 GPa) for each slip system. The layered structure of post-perovskite results in a drastic reduction in lattice friction opposed to the easiest slip systems compared to perovskite.

No MeSH data available.


Related in: MedlinePlus

Disregistry functions S(x) and the Burgers vector density ρ(x) of the [100](010) (a), [100](001) (b) and [100](011) (c) edge dislocations computed for the cation sublattice. Solid lines correspond to dislocations with positive Burgers vector; dashed lines—with negative. In case of [100](011) (c), they coincide. Evaluated value of the dislocation core half-widths ζ is given in the plot
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Fig9: Disregistry functions S(x) and the Burgers vector density ρ(x) of the [100](010) (a), [100](001) (b) and [100](011) (c) edge dislocations computed for the cation sublattice. Solid lines correspond to dislocations with positive Burgers vector; dashed lines—with negative. In case of [100](011) (c), they coincide. Evaluated value of the dislocation core half-widths ζ is given in the plot

Mentions: The computed disregistry functions S(x) and their derivatives ρ(x) have a symmetric shape for all edge dislocations described above, which was expectable from the observed dislocation core structures. All edge dislocations are characterized by the dislocation half-width ζ very close to 2b (Fig. 9a–c; Table 1) which is almost three times larger than for the [100] screw dislocations.Fig. 9


Modeling defects and plasticity in MgSiO3 post-perovskite: Part 2-screw and edge [100] dislocations.

Goryaeva AM, Carrez P, Cordier P - Phys Chem Miner (2015)

Disregistry functions S(x) and the Burgers vector density ρ(x) of the [100](010) (a), [100](001) (b) and [100](011) (c) edge dislocations computed for the cation sublattice. Solid lines correspond to dislocations with positive Burgers vector; dashed lines—with negative. In case of [100](011) (c), they coincide. Evaluated value of the dislocation core half-widths ζ is given in the plot
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4643660&req=5

Fig9: Disregistry functions S(x) and the Burgers vector density ρ(x) of the [100](010) (a), [100](001) (b) and [100](011) (c) edge dislocations computed for the cation sublattice. Solid lines correspond to dislocations with positive Burgers vector; dashed lines—with negative. In case of [100](011) (c), they coincide. Evaluated value of the dislocation core half-widths ζ is given in the plot
Mentions: The computed disregistry functions S(x) and their derivatives ρ(x) have a symmetric shape for all edge dislocations described above, which was expectable from the observed dislocation core structures. All edge dislocations are characterized by the dislocation half-width ζ very close to 2b (Fig. 9a–c; Table 1) which is almost three times larger than for the [100] screw dislocations.Fig. 9

Bottom Line: We show that despite a small tendency to core spreading in {011}, [100] screw dislocations glide very easily (Peierls stress of 1 GPa) in (010) where only Mg-O bonds are to be sheared.Whatever the planes, (010), (001) or {011}, edge dislocations are characterized by a wider core (of the order of 2b).The layered structure of post-perovskite results in a drastic reduction in lattice friction opposed to the easiest slip systems compared to perovskite.

View Article: PubMed Central - PubMed

Affiliation: Unité Matériaux et Transformations, UMR CNRS 8207, Université de Lille1, Bat C6, 59655 Villeneuve d'Ascq Cedex, France.

ABSTRACT

In this study, we propose a full atomistic study of [100] dislocations in MgSiO3 post-perovskite based on the pairwise potential parameterized by Oganov et al. (Phys Earth Planet Inter 122:277-288, 2000) for MgSiO3 perovskite. We model screw dislocations to identify planes where they glide easier. We show that despite a small tendency to core spreading in {011}, [100] screw dislocations glide very easily (Peierls stress of 1 GPa) in (010) where only Mg-O bonds are to be sheared. Crossing the Si-layers results in a higher lattice friction as shown by the Peierls stress of [100](001): 17.5 GPa. Glide of [100] screw dislocations in {011} appears also to be highly unfavorable. Whatever the planes, (010), (001) or {011}, edge dislocations are characterized by a wider core (of the order of 2b). Contrary to screw character, they bear negligible lattice friction (0.1 GPa) for each slip system. The layered structure of post-perovskite results in a drastic reduction in lattice friction opposed to the easiest slip systems compared to perovskite.

No MeSH data available.


Related in: MedlinePlus