Duwal Sakun, McCoy Chad A, Dolan Iii Daniel H, Melton Cody A, Knudson Marcus D, Root Seth, Hacking Richard, Farfan Bernardo, Johnson Christopher, Alexander C Scott, Seagle Christopher T
Sandia National Laboratories, Albuquerque, NM, 87125, USA.
Mission Support and Test Services, Albuquerque Operations, Albuquerque, NM, 87125, USA.
Sci Rep. 2022 Oct 6;12(1):16777. doi: 10.1038/s41598-022-21332-y.
Lattice and electronic structure interactions for f-electrons are fundamental challenges for lanthanide equation of state development. Difficulties in first-principles calculations, such as density functional theory (DFT), emphasize the need for well-characterized experimental data. Here, we measure in-situ x-ray diffraction of shocked samarium (Sm) and temperature along the Hugoniot for the first time, providing direct evidence for phase transitions. We report direct evidence of a distorted fcc (dfcc) phase at 23 GPa. Shocked samarium melts from the dfcc phase starting at 33 GPa (1333 K), with complete melt at 40 GPa (1468 K). Previous work indicated shock melt at 27 GPa (1200 K), underscoring the significance of x-ray measurements for detecting phase transitions. Interestingly, our observed melting is in sharp contrast with the melting reported by a diamond anvil cell study. These experimental data can tightly constrain first principles calculations and serve as key touchstones for equation of state modeling.
f 电子的晶格与电子结构相互作用是镧系元素状态方程发展面临的基本挑战。第一性原理计算（如密度泛函理论，DFT）中的困难凸显了对特征明确的实验数据的需求。在此，我们首次对冲击后的钐（Sm）进行了原位 X 射线衍射及沿雨贡纽曲线的温度测量，为相变提供了直接证据。我们报告了在 23 GPa 时存在畸变面心立方（dfcc）相的直接证据。冲击后的钐从 33 GPa（1333 K）开始从 dfcc 相熔化，在 40 GPa（1468 K）时完全熔化。先前的研究表明在 27 GPa（1200 K）时发生冲击熔化，这突出了 X 射线测量对于检测相变的重要性。有趣的是，我们观察到的熔化与金刚石对顶砧研究报告的熔化情况形成鲜明对比。这些实验数据能够严格限制第一性原理计算，并作为状态方程建模的关键试金石。
