论文标题
Hydride CEH $ _ {9} $中增强化学预压的起源
Origin of enhanced chemical precompression in cerium hydride CeH$_{9}$
论文作者
论文摘要
具有覆盖层结构的稀土金属氢化物具有很高的吸引力，因为它们具有高压下的高$ t _ {\ rm c} $超导性。最近，与其他实验合成的稀有氢化物（如LAH $ _ $ _ {10}} $ {10} $ _6 $ _6 $ _6 $相比，由CE已封闭的外壳H笼组成的CEH $ _9 $由80美元$ -100 GPA合成了80 $ -100 GPA的压力。根据密度功能理论计算，我们发现CE 5 $ P $ SEMICORE和4 $ f $/5 $ d $ d $ VALENCE State与H 1 $ S $状态强烈杂交，而电子的转移则从CE到HAMS转移到HAMS。此外，我们揭示了CE 4 $ f $电子的离域性质在覆盖物H笼的化学预压中起重要作用。我们的发现不仅表明，CE原子和H笼之间的键合特性是离子和共价的混合物，而且对理解增强化学预压的起源具有重要意义，从而导致CEH $ _9 $的合成所需的较低压力。
The rare-earth metal hydrides with clathrate structures have been highly attractive because of their promising high-$T_{\rm c}$ superconductivity at high pressure. Recently, cerium hydride CeH$_9$ composed of Ce-encapsulated clathrate H cages was synthesized at much lower pressures of 80$-$100 GPa, compared to other experimentally synthesized rare-earth hydrides such as LaH$_{10}$ and YH$_6$. Based on density-functional theory calculations, we find that the Ce 5$p$ semicore and 4$f$/5$d$ valence states strongly hybridize with the H 1$s$ state, while a transfer of electrons occurs from Ce to H atoms. Further, we reveal that the delocalized nature of Ce 4$f$ electrons plays an important role in the chemical precompression of clathrate H cages. Our findings not only suggest that the bonding nature between the Ce atoms and H cages is characterized as a mixture of ionic and covalent, but also have important implications for understanding the origin of enhanced chemical precompression that results in the lower pressures required for the synthesis of CeH$_9$.
