Stable hexagonal ternary alloy phase in Fe-Si-H at 28.6–42.2 GPa and 3000 K
Stable hexagonal ternary alloy phase in Fe-Si-H at 28.6–42.2 GPa and 3000 K
复制标题
Fe-Si-H 中稳定的六方三元合金相，在 28.6–42.2 GPa 和 3000 K 下
DOI：
10.1103/physrevb.105.104111
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发表时间：
2022
影响因子：
3.7
通讯作者：
Shim, Sang-Heon
中科院分区：
文献类型：
--
作者：
Fu, Suyu;Chariton, Stella;Prakapenka, Vitali B.;Chizmeshya, Andrew;Shim, Sang-Heon
氢(H)和硅(Si)被认为是行星核的重要轻元素。在高压下，大量的氢能够与纯铁金属合金化。硅与铁也能很好地合金化。然而，仍不确定氢与硅化铁的合金化程度，以及氢在高温高压下如何改变铁硅合金的晶体结构()。我们用脉冲激光加热和同步辐射X射线衍射技术，在42.2 GPa3000K的H介质中，对Fe-9Si和Fe-16Si合金(分别为9wt%和16wt%Si)进行了实验研究。我们发现Fe-Si合金转变为富Fe相(fcc和dhcp)、富硅相(B20和B2FeSi)和中间相()。新相具有类似于六方相的结构，但体积扩大，因此有可能掺入氢。观察到的体积膨胀和密度泛函理论计算的H含量都支持晶体结构中H/Fe≈为0.6时的大量H。由于已知在∼1300K以上，∼在18 GPa时分解，我们的结果表明，氢在高气压下稳定了六方结构。这些结果对行星核固-液界面上富Fe液体的结晶以及固体核中可能存在的化学不均质性具有一定的意义。
Hydrogen (H) and silicon (Si) are considered as important light elements for the planetary cores. A large amount of H is able to alloy with pure Fe metal at high pressures. Si can also alloy well with Fe. However, it remains uncertain how much H can alloy with iron silicides and if it alloys how H can alter the crystal structures of Fe-Si alloys at high pressures-temperatures (). We performed experiments on Fe-9Si and Fe-16Si alloys (9 and 16 wt % Si, respectively) in a H medium up to 42.2 GPa and 3000 K in diamond-anvil cells coupled with pulsed laser heating and gated synchrotron x-ray diffraction techniques. We found conversion of the Fe-Si alloys into Fe-rich (fcc and dhcp), Si-rich (B20 and B2 FeSi), and intermediate () phases. The newphase has a structure similar to the hexagonalphase but with expanded volumes, and thus, possible H incorporation. Both the observed volume expansion and the H content estimated by density-functional theory calculations support a significant amount of H with H/Fe ≈ 0.6 in the crystal structure. Becauseis known to break down above ∼1300 K at ∼18 GPa, our results suggest that hydrogen stabilizes the hexagonal structure at high. These results have implications for the crystallization of Fe-rich liquid at the solid-to-liquid boundary of planetary cores and possible existence of chemical heterogeneities in the solid cores.