High-pressure synthesis, crystal structure, and physical properties of NaB13C2 single crystals

A new boron-rich boride carbide of sodium, NaB13C2 single crystals have been successfully synthesized from the elements under high temperature and high pressure. The crystals are reddish black with a metallic luster and show a regular hexagonal prism shape. NaB13C2 crystallizes into an orthorhombic LiB13C2-type structure with a space group of Imma (No. 74) and the lattice constants are a = 10.9417 A, b = 5.6756 A, c = 8.0898 A. The crystal structure is characterized by a covalent framework of B12 icosahedra connected by CBC chains and Na atoms located in the void of the framework. The measured and calculated Raman spectra of NaB13C2 are in good agreement and show expected oscillations of the covalent framework. The electronic band structures reveal that NaB13C2 is a wide band gap semiconductor with a band gap of 3.36 eV. As a novel wide band gap semiconductor, NaB13C2 may have potential applications in semiconductor field. (c) 2021 Elsevier B.V. All rights reserved.