Collective motion in hcp-Fe at Earth’s inner core conditions
Collective motion in hcp-Fe at Earth’s inner core conditions
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DOI：
10.1073/pnas.2309952120
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发表时间：
2023-10
影响因子：
11.1
通讯作者：
Youjun Zhang;Yong Wang;Yuqian Huang;Junjie Wang;Zhixin Liang;Long Hao;Zhipeng Gao;Jun Li;Qiang Wu;Hong Zhang;Yun Liu;Jian Sun;Jung-Fu Lin
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作者：
Youjun Zhang;Yong Wang;Yuqian Huang;Junjie Wang;Zhixin Liang;Long Hao;Zhipeng Gao;Jun Li;Qiang Wu;Hong Zhang;Yun Liu;Jian Sun;Jung-Fu Lin
地球的固体内核表现出有趣的特征，如极低的剪切波速度和极低的泊松比。在这项研究中，我们使用高压-温度实验和机器学习计算来研究hcp-Fe（六方密堆积铁）在内核条件下的动力学和声速。我们的研究表明，剪切波速度急剧减少时，hcp-Fe接近熔点。我们的计算表明，铁原子在预熔区表现出快速扩散的集体运动，导致超低的剪切模量和泊松比。这些结果与地震观测和内核的地球动力学一致，表明hcp-Fe的集体运动软化了地球的固体内核。
Significance Earth’s solid inner core exhibits intriguing characteristics such as an exceptionally low shear-wave velocity and an ultrahigh Poisson's ratio. In this study, we have used high pressure–temperature experiments and machine learning calculations to examine the dynamics and sound velocities of hcp-Fe (hexagonal close-packed iron) at the inner core conditions. Our research reveals a drastic reduction in shear wave velocity when hcp-Fe approaches the melting point. Our advanced calculations show that iron atoms display collective motion with fast diffusion in the premelting regime, leading to the ultralow shear modulus and ultrahigh Poisson's ratio. These results are consistent with seismic observations and geodynamics of the inner core, demonstrating that collective motion in hcp-Fe softens Earth's solid inner core.