title: Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D'' diversity.
abstract: Recent studies show that the D'' layer, just above the Earth's core-mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D'' diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D'' discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D'' layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific.
authors.affiliation: Institute for Study of the Earth's Interior, Okayama University, Misasa, Tottori 682-0193, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yoneda
authors.affiliation: 1] Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan [2] Materials Dynamics Laboratory, RIKEN SPring-8 Center, RIKEN, Hyogo 679-5148, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukui
authors.affiliation: Institute for Study of the Earth's Interior, Okayama University, Misasa, Tottori 682-0193, Japan.
authors.forename: Fang
authors.initials: F
authors.lastname: Xu
authors.affiliation: Graduate School of Science and Engineering, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakatsuka
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshiasa
authors.affiliation: Graduate School of Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Seto
authors.affiliation: Department of Earth Sciences, University of Toyama, Toyama 930-8555, Japan.
authors.forename: Kenya
authors.initials: K
authors.lastname: Ono
authors.affiliation: Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsutsui
authors.affiliation: Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uchiyama
authors.affiliation: 1] Materials Dynamics Laboratory, RIKEN SPring-8 Center, RIKEN, Hyogo 679-5148, Japan [2] Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198, Japan.
authors.forename: Alfred Q R
authors.initials: AQ
authors.lastname: Baron
mesh_terms: D016880:Anisotropy; D017610:Calcium Compounds / Q000737:chemistry*; D018481:Convection; D003460:Crystallization; D018534:Earth, Planet; D004548:Elasticity; D055593:Geological Phenomena; D007495:Iridium / Q000737:chemistry*; D017633:Magnesium Silicates / Q000737:chemistry*; D008962:Models, Theoretical; D010087:Oxides / Q000737:chemistry*; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D017610:Calcium Compounds; D017633:Magnesium Silicates; D010087:Oxides; D007495:Iridium