Chang Xiaoju, Chen Bo, Zeng Qiyu, Wang Han, Chen Kaiguo, Tong Qunchao, Yu Xiaoxiang, Kang Dongdong, Zhang Shen, Guo Fangyu, Hou Yong, Zhao Zengxiu, Yao Yansun, Ma Yanming, Dai Jiayu
College of Science, National University of Defense Technology, Changsha, China.
Hunan Key Laboratory of Extreme Matter and Applications, National University of Defense Technology, Changsha, China.
Nat Commun. 2024 Oct 2;15(1):8543. doi: 10.1038/s41467-024-52868-4.
The immiscibility of hydrogen-helium mixture under the temperature and pressure conditions of planetary interiors is crucial for understanding the structures of gas giant planets (e.g., Jupiter and Saturn). While the experimental probe at such extreme conditions is challenging, theoretical simulation is heavily relied in an effort to unravel the mixing behavior of hydrogen and helium. Here we develop a method via a machine learning accelerated molecular dynamics simulation to quantify the physical separation of hydrogen and helium under the conditions of planetary interiors. The immiscibility line achieved with the developed method yields substantially higher demixing temperatures at pressure above 1.5 Mbar than earlier theoretical data, but matches better to the experimental estimate. Our results suggest a possibility that H-He demixing takes place in a large fraction of the interior radii of Jupiter and Saturn, i.e., 27.5% in Jupiter and 48.3% in Saturn. This indication of an H-He immiscible layer hints at the formation of helium rain and offers a potential explanation for the decrease of helium in the atmospheres of Jupiter and Saturn.
在行星内部的温度和压力条件下，氢 - 氦混合物的不混溶性对于理解气态巨行星（如木星和土星）的结构至关重要。虽然在如此极端条件下进行实验探测具有挑战性，但为了揭示氢和氦的混合行为，理论模拟被大量依赖。在此，我们通过机器学习加速分子动力学模拟开发了一种方法，以量化行星内部条件下氢和氦的物理分离。用所开发方法得到的不混溶线在压力高于1.5兆巴时产生的分层温度比早期理论数据高得多，但与实验估计值匹配得更好。我们的结果表明，在木星和土星内部半径的很大一部分区域可能发生氢 - 氦分层，即木星中为27.5%，土星中为48.3%。这种氢 - 氦不混溶层的迹象暗示了氦雨的形成，并为木星和土星大气中氦含量的减少提供了一种可能的解释。
