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1 High Pressure Science and Engineering Center, Department of Physics, University of Nevada, Las Vegas, Nevada 89154, U.S.A.
2 Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
3 Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003, U.S.A.
4 HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, U.S.A.
5 Center for Condensed Matter Science and Technology, Research Academy of Science and Technology, Harbin 150080, China
6 Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, U.S.A.
7 Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, U.S.A.
Correspondence: * E-mail: olivert{at}physics.unlv.edu
In the present study, we summarize indications for the existence of kinked post-perovskite structures in the MAS system. X-ray diffraction data and Raman spectra of aluminous magnesium metasilicate post-perovskite are inconsistent with the CaIrO3 structure. Instead the observations are consistent with structures intermediate between the perovskite and the CaIrO3 structure. Ab initio calculations show that the enthalpies of the kinked structures are slightly higher than the CaIrO3 structure at 0 K. Finite temperature, minor element chemistry, kinetics of phase transformation, and actual stress regime are plausible reasons for the observed differences between the present and the previously reported post-perovskite phases.
Key Words: Crystal structure • post-perovskite • XRD data • quantum mechanical calculation • high-pressure studies • Raman spectroscopy
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