Abstract In this paper a sp2-/sp3-hybridized cubic N-rich BN phase dubbed as B28N32 is proposed by first-principles calculations. Structurally, B28N32 is constructed by B-N bonds with different lengths, which can be considered as sp3-hybridized cubic BN blocks interlinked by sp2-hybridized N atoms. Notably, B28N32 is energetically metastable at zero pressure, but the calculated formation enthalpies against to hBN and N2 become negative at pressures above 30 GPa, indicating the viability synthesize of this N-rich compound under pressure. The stabilities of B28N32 compound at zero pressure are confirmed by phonon dispersion spectrum and Born stability criteria. Electronic band structure, density of states and electron orbits calculations show the metallic feature of B28N32 is originate from 2p electrons of sp2-hybridized N atoms, and form a unique 3D conductive network in the framework. The theoretical Vickers hardness of B28N32 estimated with two formulas is 55.3 and 40.8 GPa, respectively, which is supposed to superhard material. The proposed B28N32 enriched the B-N system in theoretically, promising in electronic devices.

中文翻译：

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具有三维金属丰度的超硬 B28N32：第一性原理预测

摘要 在本文中，通过第一性原理计算提出了一种被称为 B28N32 的 sp2-/sp3-杂化立方富氮 BN 相。在结构上，B28N32 由不同长度的 BN 键构成，可以认为是 sp3 杂化立方 BN 块，由 sp2 杂化 N 原子相互连接。值得注意的是，B28N32 在零压力下是能量亚稳态的，但计算出的对 hBN 和 N2 的形成焓在 30 GPa 以上的压力下变为负值，表明这种富氮化合物在压力下的合成活力。B28N32化合物在零压力下的稳定性通过声子色散谱和Born稳定性标准得到证实。电子能带结构、态密度和电子轨道计算表明 B28N32 的金属特征来源于 sp2 杂化 N 原子的 2p 电子，并在框架内形成独特的3D导电网络。B28N32 的理论维氏硬度用两个公式估算分别为 55.3 和 40.8 GPa，应该是超硬材料。所提出的 B28N32 在理论上丰富了 BN 系统，在电子设备中很有前景。