Morard Guillaume, Hernandez Jean-Alexis, Pege Clara, Nagy Charlotte, Libon Lélia, Lacquement Antoine, Sokaras Dimosthenis, Lee Hae Ja, Galtier Eric, Heimann Philip, Cunningham Eric, Glenzer Siegfried H, Vinci Tommaso, Prescher Clemens, Boccato Silvia, Chantel Julien, Merkel Sébastien, Zhang Yanyao, Yang Hong, Wei Xuehui, Pandolfi Silvia, Mao Wendy L, Gleason Arianna E, Shim Sang Heon, Alonso-Mori Roberto, Ravasio Alessandra
ISTerre, Université Grenoble Alpes, CNRS, Grenoble, France.
Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, France.
Nat Commun. 2024 Oct 3;15(1):8483. doi: 10.1038/s41467-024-51796-7.
Molten silicates at depth are crucial for planetary evolution, yet their local structure and physical properties under extreme conditions remain elusive due to experimental challenges. In this study, we utilize in situ X-ray diffraction (XRD) at the Matter in Extreme Conditions (MEC) end-station of the Linear Coherent Linac Source (LCLS) at SLAC National Accelerator Laboratory to investigate liquid silicates. Using an ultrabright X-ray source and a high-power optical laser, we probed the local atomic arrangement of shock-compressed liquid (Mg,Fe)SiO with varying Fe content, at pressures from 81(9) to 385(40) GPa. We compared these findings to ab initio molecular dynamics simulations under similar conditions. Results indicate continuous densification of the O-O and Mg-Si networks beyond Earth's interior pressure range, potentially altering melt properties at extreme conditions. This could have significant implications for early planetary evolution, leading to notable differences in differentiation processes between smaller rocky planets, such as Earth and Venus, and super-Earths, which are exoplanets with masses nearly three times that of Earth.
深部的熔融硅酸盐对行星演化至关重要，但由于实验挑战，它们在极端条件下的局部结构和物理性质仍然难以捉摸。在本研究中，我们利用位于SLAC国家加速器实验室的直线相干直线加速器光源（LCLS）的极端条件物质（MEC）实验站的原位X射线衍射（XRD）来研究液态硅酸盐。使用超亮X射线源和高功率光学激光，我们在81（9）至385（40）吉帕的压力下，探测了不同铁含量的冲击压缩液态（Mg，Fe）SiO的局部原子排列。我们将这些发现与相似条件下的从头算分子动力学模拟进行了比较。结果表明，在超过地球内部压力范围时，O-O和Mg-Si网络会持续致密化，这可能会改变极端条件下的熔体性质。这可能对早期行星演化产生重大影响，导致较小的岩石行星（如地球和金星）与超级地球（质量几乎是地球三倍的系外行星）之间的分化过程出现显著差异。
