Huang Haijun, Fan Lili, Liu Xun, Xu Feng, Wu Ye, Yang Gang, Leng Chunwei, Wang Qingsong, Weng Jidong, Wang Xiang, Cai Lingcang, Fei Yingwei
School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China.
National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China.
Nat Commun. 2022 Feb 1;13(1):616. doi: 10.1038/s41467-022-28255-2.
Knowledge of the sound velocity of core materials is essential to explain the observed anomalously low shear wave velocity (V) and high Poisson's ratio (σ) in the solid inner core. To date, neither V nor σ of Fe and Fe-Si alloy have been measured under core conditions. Here, we present V and σ derived from direct measurements of the compressional wave velocity, bulk sound velocity, and density of Fe and Fe-8.6 wt%Si up to ~230 GPa and ~5400 K. The new data show that neither the effect of temperature nor incorporation of Si would be sufficient to explain the observed low V and high σ of the inner core. A possible solution would add carbon (C) into the solid inner core that could further decrease V and increase σ. However, the physical property-based Fe-Si-C core models seemingly conflict with the partitioning behavior of Si and C between liquid and solid Fe.
了解核心物质的声速对于解释在固态内核中观测到的异常低的剪切波速度（V）和高泊松比（σ）至关重要。迄今为止，铁（Fe）和铁硅（Fe-Si）合金的V和σ在核心条件下均未被测量。在此，我们展示了通过直接测量铁和含8.6 wt%硅的铁（Fe-8.6 wt%Si）在高达约230 GPa和约5400 K时的纵波速度、体声速和密度而得出的V和σ。新数据表明，温度效应和硅的掺入都不足以解释观测到的内核低V和高σ。一个可能的解决方案是在固态内核中添加碳（C），这可能会进一步降低V并提高σ。然而，基于物理性质的Fe-Si-C核心模型似乎与硅和碳在液态和固态铁之间的分配行为相冲突。
