Pseudogap Control of Physical and Chemical Properties in CeFeSi-Type Intermetallics
Pseudogap Control of Physical and Chemical Properties in CeFeSi-Type Intermetallics
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CeFeSi型金属间化合物物理和化学性质的赝间隙控制
DOI：
10.1021/acs.inorgchem.8b03539
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发表时间：
2019
影响因子：
4.6
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Wu, Jiazhen;Lu, Erdong;Li, Jiang;Lu, Yangfan;Kitano, Masaaki;Fredrickson, Daniel C.;Inoshita, Takeshi;Hosono, Hideo
我们描述了新型三元化合物 CaRuSi 的合成，其化学和物理性质有助于清楚地了解电子结构如何控制金属间化合物同构系列的行为。 DFT 计算表明，费米能级 (EF) 附近出现电子赝能隙，相当于每个 RuSi 单元 14 个价电子。通过与 CaCoSi（15 个电子）的电子结构（其中 EF 位于相应的赝能隙上方）及其氢化物 CaCoSiH（其中 H 阴离子的形成恢复了金属亚晶格上的 14 电子计数，使 EF 回到赝能隙之上）的电子结构进行比较，进一步研究了闭壳状特征。 14 电子赝能隙的化学起源可以通过反向近似分子轨道分析来解释。在这里，赝能隙显示出与配位化学的 d8square 平面配合物等瓣的 Ru 16 电子构型的填充（但其中 4 个电子对在 Ru 原子之间共价共享，因此只需要 12 个电子），以及 Si 孤对对（2 个电子）的占据。实验上，赝能隙通过热容测量得到证实，这表明 14 电子系统 CaRuSi 和 CaCoSiH 各自在 EF 处表现出比 15 电子系统 CaCoSi 更小的电子态密度。重要的是，14 电子赝能隙也显着影响化合物的化学性质，氢解吸测量中观察到的 CaCoSiH 和 CaRuSiH 稳定性的差异证明了这一点。这些结果可能支持用于超导、储氢和涉及氢化的催化的功能材料的设计。
We describe the synthesis of the new ternary compound CaRuSi whose chemical and physical properties help draw a clear picture of how electronic structure controls the behavior of an isostructural series of intermetallics. DFT calculations reveal that an electronic pseudogap arises near the Fermi level (EF), corresponding to 14 valence electrons per RuSi unit. The closed-shell-like character is further investigated by comparisons with the electronic structures of CaCoSi (15 electrons), where theEFlies above the corresponding pseudogap, and its hydride CaCoSiH, where formation of H anions restores the 14-electron count on the metal sublattice, returning theEFto the pseudogap. The chemical origin of the 14-electron pseudogap is interpreted with a reversed approximation Molecular Orbital analysis. Here, the pseudogap is shown to coincide with the filling of Ru 16 electron configurations isolobal to the d8square planar complexes of coordination chemistry (but where 4 electron pairs are shared covalently between Ru atoms such that only 12 electrons are required), and the occupation of Si lone pairs (2 electrons). Experimentally, the pseudogap is confirmed with heat capacity measurements, which indicate that the 14-electron systems CaRuSi and CaCoSiH each exhibit a smaller electronic density of states at theEFthan the 15-electron system CaCoSi. Importantly, the 14-electron pseudogap also significantly affects the chemical properties of the compounds, as evidenced by the difference in the stabilities of CaCoSiH and CaRuSiH observed in hydrogen desorption measurements. These results may support the design of functional materials for superconductivity, hydrogen storage, and catalysis involving hydrogenation.