Yox Philip, Lee Shannon J, Wang Lin-Lin, Jing Dapeng, Kovnir Kirill
Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.
Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States.
Inorg Chem. 2021 Apr 19;60(8):5627-5634. doi: 10.1021/acs.inorgchem.0c03636. Epub 2021 Apr 1.
Two novel layered compounds BaCuSiPn (Pn = P, As) adopting new structure types are reported. As revealed by single-crystal X-ray diffraction, both compounds are composed of unique Cu-Si-Pn layers featuring CuPn and SiPn structural motifs found in other archetypal pnictide materials. The stacking of the isostructural Cu-Si-Pn layers is different for phosphide and arsenide compounds. Synthesis from elements aided by synchrotron powder X-ray diffraction resulted in the obtainment of bulk powders with a minimized amount of admixtures. Experimentally measured physical properties of BaCuSiAs unexpectedly showed metal-like behavior at temperatures above 15 K, despite the fact that density functional theory calculations predict a small band gap of 0.4 eV. BaCuSiAs exhibits ultralow thermal conductivity, which can be explained by the combination of a layered crystal structure with alternating covalent and ionic bonding, which feature rattling of Cu atoms similar to that in tetrahedrites.
报道了两种采用新结构类型的新型层状化合物BaCuSiPn（Pn = P，As）。单晶X射线衍射表明，这两种化合物均由独特的Cu-Si-Pn层组成，这些层具有在其他典型磷化物材料中发现的CuPn和SiPn结构单元。磷化物和砷化物化合物中同构的Cu-Si-Pn层的堆积方式不同。借助同步辐射粉末X射线衍射由元素合成得到了具有最少杂质含量的块状粉末。尽管密度泛函理论计算预测BaCuSiAs的带隙为0.4 eV，但实验测量的BaCuSiAs的物理性质在15 K以上的温度下意外地表现出类似金属的行为。BaCuSiAs表现出超低的热导率，这可以通过具有交替共价键和离子键的层状晶体结构的组合来解释，这种结构具有类似于黝铜矿中Cu原子的晃动。
