Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO3 orthopyroxene.
Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO3 orthopyroxene.
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DOI：
10.1073/pnas.0506811103
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发表时间：
2006-02
影响因子：
11.1
通讯作者：
S. Shieh;T. Duffy;A. Kubo;G. Shen;V. Prakapenka;N. Sata;K. Hirose;Y. Ohishi
中科院分区：
文献类型：
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作者：
S. Shieh;T. Duffy;A. Kubo;G. Shen;V. Prakapenka;N. Sata;K. Hirose;Y. Ohishi
利用激光加热金刚石对顶砧装置，研究了由天然辉石合成的后钙钛矿（ppv，CaIrO（3）型）相的稳定性和状态方程FeSiO（3）。当K '（0）= 4时，我们测量的PPV相的压力-体积数据从12-106 GPa产生219（5）GPa的体积模量和164.9（6）A（3）的零压力体积。在100 GPa的压力下，ppv的体积模量为575（15）GPa。Fe的存在降低了转变压力。我们的X射线衍射数据表明ppv相可以在P > 109（4）GPa和2，400（400）K下形成，对应于核幔边界上方约400-550 km。在80-106 GPa下共存的钙钛矿和CaIrO（3）型相的体积的直接比较表明，ppv相的体积比钙钛矿小1.1（2）%。使用测得的体积与体积模量计算状态方程拟合，我们发现，体积声速下降了2.3（2.1）%，在120 GPa的过渡。在不进一步加热的情况下减压时，发现在低至12 GPa的压力下仍然可以观察到PPV相，并且还报告了至少部分持久存在于环境条件的证据。
Using the laser-heated diamond anvil cell, we investigate the stability and equation of state of the postperovskite (ppv, CaIrO(3)-type) phase synthesized from a natural pyroxene composition with 9 mol.% FeSiO(3). Our measured pressure-volume data from 12-106 GPa for the ppv phase yield a bulk modulus of 219(5) GPa and a zero-pressure volume of 164.9(6) A(3) when K'(0) = 4. The bulk modulus of ppv is 575(15) GPa at a pressure of 100 GPa. The transition pressure is lowered by the presence of Fe. Our x-ray diffraction data indicate the ppv phase can be formed at P > 109(4) GPa and 2,400(400) K, corresponding to approximately 400-550 km above the core-mantle boundary. Direct comparison of volumes of coexisting perovskite and CaIrO(3)-type phases at 80-106 GPa demonstrates that the ppv phase has a smaller volume than perovskite by 1.1(2)%. Using measured volumes together with the bulk modulus calculated from equation of state fits, we find that the bulk sound velocity decreases by 2.3(2.1)% across this transition at 120 GPa. Upon decompression without further heating, it was found that the ppv phase could still be observed at pressures as low at 12 GPa, and evidence for at least partial persistence to ambient conditions is also reported.