Layered Transition Metal Electride Hf$_{2}$Se with Coexisting Two-Dimensional Anionic $d$-Electrons and Hf–Hf Metallic Bonds
Xihui Wang1†, Xiaole Qiu2†, Chang Sun1, Xinyu Cao1, Yujie Yuan1, Kai Liu2*, and Xiao Zhang1*
1State Key Laboratory of Information Photonics and Optical Communications & School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China 2Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
Abstract：Electrides are unique materials, whose anionic electrons are confined to interstitial voids, and they have broad potential applications in various areas. In contrast to the majority of inorganic electrides, in which the anionic electrons primarily consist of $s$-electrons of metals, electrides with anionic $d$-electrons are very rare. Based on first-principles electronic structure calculations, we predict that the layered transition metal chalcogenide Hf$_{2}$Se is a novel electride candidate with anionic $d$-electrons. Our results indicate that the anionic electrons confined in the Hf$_{6}$ octahedra vacancy between [Hf$_{2}$Se] layers mainly come from the Hf-5$d$ orbitals. In addition, the anionic electrons coexist with the Hf–Hf multiple-center metallic bonds located in the center of neighboring Hf$_{4}$ tetrahedra. The calculated work function (3.33 eV) for the (110) surface of Hf$_{2}$Se is slightly smaller than that of Hf$_{2}$S, which has recently been reported to exhibit good electrocatalytic performance. Our study of Hf$_{2}$Se will enrich the electride family, and promote further research into the physical properties and applications of electrides.
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2021, Vol. 38 
