Abstract
The post-perovskite phase of (Mg,Fe)SiO3 is believed to be the main mineral phase of the Earth's lowermost mantle (the D″ layer). Its properties explain1,2,3,4,5,6 numerous geophysical observations associated with this layer—for example, the D″ discontinuity7, its topography8 and seismic anisotropy within the layer9. Here we use a novel simulation technique, first-principles metadynamics, to identify a family of low-energy polytypic stacking-fault structures intermediate between the perovskite and post-perovskite phases. Metadynamics trajectories identify plane sliding involving the formation of stacking faults as the most favourable pathway for the phase transition, and as a likely mechanism for plastic deformation of perovskite and post-perovskite. In particular, the predicted slip planes are {010} for perovskite (consistent with experiment10,11) and {110} for post-perovskite (in contrast to the previously expected {010} slip planes1,2,3,4). Dominant slip planes define the lattice preferred orientation and elastic anisotropy of the texture. The {110} slip planes in post-perovskite require a much smaller degree of lattice preferred orientation to explain geophysical observations of shear-wave anisotropy in the D″ layer.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Murakami, M., Hirose, K., Kawamura, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition in MgSiO3 . Science 304, 855–858 (2004)
Oganov, A. R. & Ono, S. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D″ layer. Nature 430, 445–448 (2004)
Iitaka, T., Hirose, K., Kawamura, K. & Murakami, M. The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle. Nature 430, 442–445 (2004)
Tsuchiya, T., Tsuchiya, J., Umemoto, K. & Wentzcovitch, R. M. Elasticity of post-perovskite MgSiO3 . Geophys. Res. Lett. 31, L14603 (2004)
Hernlund, J. W., Thomas, C. & Tackley, P. J. A doubling of the post-perovskite phase boundary and structure of the Earth's lowermost mantle. Nature 434, 882–886 (2005)
Ono, S. & Oganov, A. R. In situ observations of phase transition between perovskite and CaIrO3-type phase in MgSiO3 and pyrolitic mantle composition. Earth Planet. Sci. Lett. 236, 914–932 (2005)
Lay, T. & Helmberger, D. V. A shear velocity discontinuity in the lower mantle. Geophys. Res. Lett. 10, 63–66 (1983)
Lay, T., Williams, Q. & Garnero, E. J. The core-mantle boundary layer and deep Earth dynamics. Nature 392, 461–468 (1998)
Panning, M. & Romanowicz, B. Inferences on flow at the base of Earth's mantle based on seismic anisotropy. Science 303, 351–353 (2004)
Karato, S., Zhang, S. Q. & Wenk, H. R. Superplasticity in Earth's lower mantle—evidence from seismic anisotropy and rock physics. Science 270, 458–461 (1995)
Cordier, P., Ungar, T., Zsoldos, L. & Tichy, G. Dislocation creep in MgSiO3 perovskite at conditions of the Earth's uppermost lower mantle. Nature 428, 837–840 (2004)
Nakagawa, T. & Tackley, P. J. Effects of a perovskite-post perovskite phase change near core-mantle boundary in compressible mantle convection. Geophys. Res. Lett. 31, L16611 (2004)
Martoňák, R., Laio, A. & Parrinello, M. Predicting crystal structures: The Parrinello-Rahman method revisited. Phys. Rev. Lett. 90, 075503 (2003)
Martoňák, R. et al. Simulation of structural phase transitions by metadynamics. Z. Kristallogr. 220, 489–498 (2005)
Laio, A. & Parrinello, M. Escaping free-energy minima. Proc. Natl Acad. Sci. USA 99, 12562–12566 (2002)
Oganov, A. R., Brodholt, J. P. & Price, G. D. Comparative study of quasiharmonic lattice dynamics, molecular dynamics and Debye model in application to MgSiO3 perovskite. Phys. Earth Planet. Inter. 122, 277–288 (2000)
Smith, W., Todorov, I. T. & Leslie, M. The DL_POLY molecular dynamics package. Z. Kristallogr. 220, 563–567 (2005)
Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane wave basis set. Phys. Rev. B 54, 11169–11186 (1996)
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996)
Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994)
Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B59, 1758–1775 (1999)
Vinet, P., Rose, J. H., Ferrante, J. & Smith, J. R. Universal features of the equation of state of solids. J. Phys. Condens. Matter 1, 1941–1963 (1989)
Legrand, B. Relations entre la structure èlectronique et la facilitè de glissement dans les métaux hexagonaux compacts. Phil. Mag. 49, 171–184 (1984)
Montagner, J.-P. & Nataf, H.-C. A simple method for inverting the azimuthal anisotropy of surface waves. J. Geophys. Res. 91, 511–520 (1986)
Tsuchiya, T., Tsuchiya, J., Umemoto, K. & Wentzcovitch, R. M. Phase transition in MgSiO3 perovskite in the earth's lower mantle. Earth Planet. Sci. Lett. 224, 241–248 (2004)
Garnero, E. J., Maupin, V., Lay, T. & Fouch, M. J. Variable azimuthal anisotropy in Earth's lowermost mantle. Science 306, 259–261 (2004)
Wookey, J., Kendall, J.-M. & Rümpker, G. Lowermost mantle anisotropy beneath the north Pacific from differential S-ScS splitting. Geophys. J. Int. 161, 829–838 (2005)
Acknowledgements
Calculations were performed at ETH Zurich and CSCS (Manno). A.R.O. is grateful to P. Cordier, T. Ungar, G. Ferraris, T. Balic-Zunic, E. Makovicky and C. Thomas for discussions on various aspects of this work. Author Contributions A.R.O. designed and performed this work and wrote the paper. Many ideas on plasticity and phase transformation mechanisms arose from discussions between A.R.O., R.M., A.L. and M.P.; R.M. and P.R. assisted A.R.O. in technical aspects of this work.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
Supplementary information
Supplementary Figure 1
This figure shows ab- and bc- projections of perfect post-perovskite (top) and post-perovskite with the {010} stacking fault (bottom). This stacking fault turns out to be very unfavourable. As discussed in the paper, the {110} stacking faults are preferred instead. SiO6 octahedra are shown in blue, Mg atoms are large pink spheres, Si atoms are small blue spheres, O atoms are small red spheres. (PDF 131 kb)
Rights and permissions
About this article
Cite this article
Oganov, A., Martoňák, R., Laio, A. et al. Anisotropy of Earth's D″ layer and stacking faults in the MgSiO3 post-perovskite phase. Nature 438, 1142–1144 (2005). https://doi.org/10.1038/nature04439
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/nature04439
This article is cited by
-
Pathways for the formation of ice polymorphs from water predicted by a metadynamics method
Scientific Reports (2020)
-
Kinetics and detectability of the bridgmanite to post-perovskite transformation in the Earth's D″ layer
Nature Communications (2019)
-
Seismic anisotropy of the D″ layer induced by (001) deformation of post-perovskite
Nature Communications (2017)
-
First-principles calculations of elasticity of minerals at high temperature and pressure
Science China Earth Sciences (2016)
-
Modeling defects and plasticity in MgSiO3 post-perovskite: Part 1—generalized stacking faults
Physics and Chemistry of Minerals (2015)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.