Structure, Stability, and Electronic Properties of Boron Suboxide: A Density Functional Theory Study,The Journal of Physical Chemistry C

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Structure, Stability, and Electronic Properties of Boron Suboxide: A Density Functional Theory Study
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2022-09-13 , DOI: 10.1021/acs.jpcc.2c05590
Bin Liu ₁ , Dylan Evans ₁ , Hao Deng ₁ , James Edgar ₁

Affiliation

Boron suboxide (B₆O) is a boron-rich compound derived from the α-rhombohedral boron lattice with extreme hardness and unusual semiconducting properties. In this work, density functional theory (DFT) was used to show that unit cell volume, mechanical strength, band gaps, and thermodynamic stabilities of B₆O were influenced by the interstitial elements and point defects at the icosahedral sites. While the hexagonal unit cell volume (HUCV) varies with interstitial occupancy, it is the icosahedral defect that weakens the intrinsic bulk modulus of B₆O. Using the hybrid HSE functional, we confirmed that the perfect B₆O bulk is a p-type semiconductor with a direct band gap of 2.8 eV. Furthermore, by screening α-boron compounds systematically, we found that a simple octet rule may offer a consistent explanation for the variations in the computed electronic structures. The formation free energies calculated over a wide range of temperatures (0–2500 K) and pressures (0–80 GPa) predict that formations of interstitial defects become favorable only at higher temperatures (ca. 1800 K) in bulk B₆O lattices. The nudged elastic band (NEB) method was employed to identify the minimum energy pathways for the diffusions of dislocated B and O atoms. The diffusion of icosahedral B atoms has an energy barrier of 0.16 eV. More complex B diffusion paths involving the reorganization of icosahedral boron atoms incur higher barriers (>1 eV). In contrast, the diffusion of interstitial O atoms is facile with a barrier of 0.4 eV. Lastly, successive O insertions into the α-B lattice were performed using DFT to generate a basic understanding of the oxidation process. These calculations provide fundamental atomistic insights into the growth of B₆O crystals and control of their point defects.

中文翻译：

低氧化硼的结构、稳定性和电子特性：密度泛函理论研究

低氧化硼 (B ₆ O) 是一种富含硼的化合物，源自 α-菱面体硼晶格，具有极高的硬度和不同寻常的半导体特性。_{在这项工作中，密度泛函理论 (DFT) 用于表明 B 6} O 的晶胞体积、机械强度、带隙和热力学稳定性受二十面体位点的间隙元素和点缺陷的影响。虽然六边形晶胞体积 (HUCV) 随间隙占用而变化，但正是二十面体缺陷削弱了 B ₆ O 的固有体积模量。使用混合 HSE 泛函，我们证实了完美的 B ₆O bulk 是一种 p 型半导体，直接带隙为 2.8 eV。此外，通过系统地筛选 α-硼化合物，我们发现一个简单的八位组规则可以为计算的电子结构的变化提供一致的解释。在很宽的温度 (0–2500 K) 和压力 (0–80 GPa) 范围内计算的地层自由能预测，间隙缺陷的形成仅在 B _{6的较高温度（约 1800 K）下变得有利}O格子。采用轻推弹性带 (NEB) 方法来确定位错 B 和 O 原子扩散的最小能量路径。二十面体 B 原子的扩散具有 0.16 eV 的能垒。涉及二十面体硼原子重组的更复杂的 B 扩散路径会产生更高的势垒 (>1 eV)。相比之下，间隙 O 原子的扩散很容易，势垒为 0.4 eV。最后，使用 DFT 将 O 连续插入到 α-B 晶格中，以对氧化过程有一个基本的了解。_{这些计算为 B 6} O 晶体的生长及其点缺陷的控制提供了基本的原子论见解。

更新日期：2022-09-13

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