标题： 超高压下I-42d型镁橄榄石(Mg₂SiO₄)中铁的自旋状态 显示英文标题

标题： Spin state of iron in I-42d-type Mg2SiO4 at ultra-high pressures

摘要： 在约 500 GPa 的极端压力下，即超级地球深内部的特征条件，据报道，NaCl 型 MgO 和后钙钛矿型 MgSiO₃ (PPv) 的组合会产生一种具有 I-42d 对称性的 Mg₂SiO₄ 后 PPv 相。 这种后 PPv (pppv) 硅酸盐被提议为这些巨大的岩石系外行星的主要地幔硅酸盐。 理解 pppv 的基本性质，特别是与 Fe₂SiO₄ 的固溶体，对于了解此类行星的内部动力学和组成至关重要。 在这项研究中，我们对从 400 GPa 到 1 TPa 的压力范围内含 Fe²⁺ 的 pppv 的性质进行了从头算研究。 考虑到铁中 3d 电子的局域特性，我们采用了 LDA+Usc 方法以及传统的 DFT 泛函来探测该系统的电子结构。 仔细评估了 Hubabrd 参数 U 随体积和自旋态的变化关系。 此外，我们系统性地探索了压力、温度和结构变化对含 Fe²⁺ 的 pppv 中铁自旋态的影响，为改进超级地球型系外行星的地幔建模提供了有价值的数据。 显示英文摘要

摘要： At extreme pressures of approximately 500 GPa, conditions characteristic of the deep interiors of super-Earths, the combination of NaCl-type MgO and post-perovskite-type MgSiO3 (PPv) has been reported to produce a post-PPv phase of Mg2SiO4 with an I-42d symmetry. This post-PPv (pppv) silicate is proposed as the primary mantle silicate in these massive rocky exoplanets. Understanding the fundamental properties of pppv, particularly in solid solutions with Fe2SiO4, is crucial for insights into the interior dynamics and compositions of such planets. In this study, we conduct an ab initio investigation of the properties of Fe2+-bearing pppv at pressures ranging from 400 GPa to 1 TPa. Given the localized nature of 3d-electrons in iron, we employ the LDA+Usc method alongside conventional DFT functionals to probe the electronic structure of this system. The dependence of the Hubbard parameter U on volume and spin state is carefully evaluated. Furthermore, we systematically explore the effects of pressure, temperature, and structural variations on the spin state of iron in Fe2+-bearing pppv, providing valuable data to improve mantle modeling for super-Earth-type exoplanets.