Yajima Takeshi, Nakajima Hotaka, Honda Takashi, Ikeda Kazutaka, Otomo Toshiya, Takeda Hikaru, Hiroi Zenji
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
Inorg Chem. 2020 Apr 6;59(7):4228-4233. doi: 10.1021/acs.inorgchem.9b02810. Epub 2020 Mar 6.
We present the high-pressure synthesis and crystal structure of a novel titanium hydride complex, BaCaTiH, with 9-fold coordination. It comprises a unique dinuclear [TiH] complex that consists of a pair of Ti ions each coordinated by nine hydrides in the monocapped square antiprism, distinguished from the known 9-fold coordination in the mononuclear tricapped trigonal prism of [MH]. The dinuclear hydride complex is stabilized by three-center two-electron bonding at the four bridging Ti-H-Ti bonds to compensate for the lack of valence electrons in the Ti ions. Optical measurements show that BaCaTiH is a band insulator with a wide band gap of 2.25 eV. Density functional theory calculations reveal that the top of the valence band is dominated by H-1s-derived states, as expected from the 9-fold coordination, which would present a playground for electronic properties such as high- superconductivity when doped with hole carriers or under high pressure.
我们展示了一种新型氢化钛配合物BaCaTiH的高压合成及其晶体结构，该配合物具有九配位结构。它包含一种独特的双核[TiH]配合物，由一对Ti离子组成，每个Ti离子在单帽四方反棱柱中由九个氢化物配位，这与已知的单核三帽三角棱柱[MH]中的九配位不同。双核氢化物配合物通过四个桥连Ti-H-Ti键处的三中心两电子键稳定，以补偿Ti离子中价电子的不足。光学测量表明，BaCaTiH是一种带隙为2.25 eV的宽带绝缘体。密度泛函理论计算表明，价带顶由H-1s衍生态主导，这与九配位预期一致，当掺杂空穴载流子或在高压下时，这将为诸如高超导性等电子性质提供一个研究平台。
