Exploring the electronic, mechanical, and anisotropy properties of novel tetragonal B 2 CO phase
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School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China; and State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China 3 State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China 4 School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 51006, China a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] 2
Received: 1 July 2019; accepted: 19 August 2019
A novel tetragonal B2CO structure (tP16-B2CO), formed by strong covalent sp2–sp3 B–C and B–O bonds, was predicted with aid of an unbiased structure searching method. With the energy lower than those of previously proposed candidates, except oI16-B2CO, tP16-B2CO was identified as the thermodynamic metastable phase for B2CO compound. The elastic matrix and phonon dispersion spectra declare that tP16-B2CO is mechanically and dynamically stable. The electronic band structure calculation at ambient pressure and a series of high pressure has manifested the indirect semiconducting and band gap increases first and then decreases with pressure increases. The calculation of mechanical properties such as hardness and stress–strain relations of tP16 structure revealed its common hard nature with high hardness of 23.19 GPa and anisotropy with the max stress along [001] is far higher than that along [100].
Introduction In a sense, the structure of a material resolves its performance. For example, two common allotropes of carbon material, diamond and graphite, have completely contradictory properties: diamond is transparent, nonconductive, and superhard, whereas graphite is opaque, conductive, and slippery. Therefore, structural design and performance study play an important role in the research of materials, especially hard materials. As typical hard and superhard materials with strong sp3 covalent bonds [1], the B–C–O system compounds attracted great attention since B–C–O system compounds with nonstoichiometric ratio compositions B(C, O)0.155, B6C1.1O0.33, and B6C1.28O0.31 have been synthesized [2, 3, 4]. Because of an unclear structural and atomic information of the synthesized sample, the development of mechanical properties and industrial applications of B–C–O compounds has been seriously hindered. Then, attention has been turn to the theoretical research, and great progress has been made [5]. Considering the wide variety of B–C–O compounds, Li took B2CO as an example, which is the simplest compound in
ª Materials Research Society 2019
the B–C–O system and is isoelectronic with diamond, and creatively proposed two kinds of tetragonal superhard phases, namely, tP4-B2CO and tP16-B2CO by combining the structure prediction program with the first-principles method [6]. All nonequivalent atoms in each B2CO compou
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