2018 年 47 巻 1 号 p. 27-33
The equation of state (EoS) at multi-megabar condition should include a parameter at infinite pressure such as K′∞ in Keane EoS. The Keane EoS model was adopted for the first time to extract meaningful physical properties for MgSiO3 post-perovskite (PPv) phase. The thermal EoSs of PPv were determined by using both laser-heated diamond anvil cell and density-functional theoretical techniques, within a multi-megabar pressure range, corresponding to the conditions of a super-Earth's mantle. The experimentally determined Grüneisen parameter, which is one of the thermal EoS parameters, and its volume dependence were consistent with their theoretically obtained values. Both the experimental and theoretical EoS were also found to be in very good agreement for volumes up to 300 GPa and 5000 K, respectively. Our newly developed EoS is applicable to a super-Earth's mantle, as well as the Earth's core-mantle boundary region. On the other hand, the double stage diamond anvil cell (ds-DAC) technique was developed using a focused ion beam (FIB) system in order to generate the Tera pascal (TPa) regime corresponding to conditions of exoplanet's interior. Micro-manufacturing using a FIB system enables us to control shapes of 2nd stage micro-anvils, process any materials, including nano-polycrystalline diamond (NPD) and single crystal diamond, and assemble the sample exactly in a very small space between the 2nd stage anvils. This method is highly reproducible and would allow us to open a new frontier.