• journal_title：American Mineralogist
• Contributor：Tiziana Boffa Ballaran ; Reidar G. Trønnes ; Daniel J. Frost
• Publisher：Mineralogical Society of America
• Date：2007-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2007.2715
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：92
• issue：10
• firstpage：1760
• section：Letters

Unit-cell lattice parameters have been measured to ~8 GPa in a diamond anvil cell for two single crystals of CaIrO₃: one with the perovskite (Pbnm) and the other with the post-perovskite (Cmcm) structure. The CaIrO₃ post-perovskite structure is more compressible than the perovskite. A third-order Birch Murnaghan equation of state has been used to fit the measured P-V data with the following refined parameters: V₀ = 229.463(8) ų, K₀ = 198(3) GPa, K’ = 1.2(8); and V₀ = 226.38(1) ų, K₀ = 181(3) GPa, K’ = 2.3(8) for CaIrO₃ perovskite and post-perovskite, respectively. The compressibility of the unit-cell axes of the perovskite structure is highly anisotropic with β_a >> β_c >> β_b. In contrast, the trong>btrong> axis is the most compressible in the post-perovskite structure, whereas the trong>atrong> and trong>ctrong> axes have similar compressibilities (with trong>ctrong> slightly less compressible than trong>atrong>) and are much stiffer. A comparison between the compressibility of CaIrO₃ perovskite and post-perovskite with the isostructural MgSiO₃ phases, reveals a similar general behavior, although in detail CaIrO₃ perovskite is more and the post-perovskite less anisotropic than the corresponding MgSiO₃ compounds.