Revision 1 ( correction date : 2013-5-10 ) 1 Cubic perovskite polymorph of strontium metasilicate at high pressures 2

1 Cubic perovskite polymorph of strontium metasilicate at high pressures 2 Wansheng Xiao, Dayong Tan, Wei Zhou, Jing Liu, and Jian Xu 3 4 1 Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese 5 Academy of Sciences, Guangzhou 510640, China 6 2 Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 7 3 Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; and 8 Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China 9 10 ABSTRACT 11 By using a diamond anvil cell (DAC) with laser heating technology, a cubic 12 perovskite polymorph of SrSiO3 has been synthesized at ~38 GPa and 1500-2000 K at 13 the first time. The P, V data of this new phase yield its lattice volume and bulk 14 modulus at ambient conditions of V0 = 49.18(5) Å, K0 = 211(3) GPa, respectively, 15 when they are fitted against the Birch-Murnaghan equation of state with a fixed K0’ at 16 4. On decompression, the SrSiO3 cubic perovskite phase becomes unstable at ~6.2 17 GPa and disappears completely at ~4.7 GPa. The transformed product can be 18 considered as an amorphous phase with a minor amount of small size crystals in the 19 amorphous matrix when the pressure is released to ambient conditions. The first 20 principle calculations predicted the structural properties of both the cubic and the 21 six-layer-repeated hexagonal perovskite polymorphs of SrSiO3 and the 22 pressure-induced phase transition very well with the experimental results. At high 23 pressures, the experimental and theoretical results indicate that the larger Sr cation 24 can substitute the Ca cation and enter into the lattice of CaSiO3 cubic perovskite in 25 the lower mantle conditions with a small lattice strain. It is a good illustration that the 26 Sr atom prefers entering the CaSiO3 cubic perovskite and higher amount of Sr in the 27 inclusion minerals of CaSiO3 perovskite and its related modifications in diamonds 28 originating from the lower mantle. 29 30 This is a preprint, the final version is subject to change, of the American Mineralogist (MSA) Cite as Authors (Year) Title. American Mineralogist, in press. (DOI will not work until issue is live.) DOI: http://dx.doi.org/10.2138/am.2013.4470 7/3