Nanotwinned Boron Suboxide (B6O): New Ground State of B6O

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• 作者：Qi An ; K. Madhav Reddy ; Huafeng Dong ; Ming-Wei Chen ; Artem R. Oganov ; William A. Goddard III
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：July 13, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：4236-4242
• 全文大小：571K
• 年卷期：0
• ISSN：1530-6992

文摘

Nanotwinned structures in superhard ceramics rhombohedral boron suboxide (R-B₆O) have been examined using a combination of transmission electron microscopy (TEM) and quantum mechanics (QM). QM predicts negative relative energies to R-B₆O for various twinned R-B₆O (denoted as τ-B₆O, 2τ-B₆O, and 4τ-B₆O), consistent with the recently predicted B₆O structure with Cmcm space group (τ-B₆O) which has an energy 1.1 meV/B₆O lower than R-B₆O. We report here TEM observations of this τ-B₆O structure, confirming the QM predictions. QM studies under pure shear deformation and indentation conditions are used to determine the deformation mechanisms of the new τ-B₆O phase which are compared to R-B₆O and 2τ-B₆O. The lowest stress slip system of τ-B₆O is (010)/⟨001⟩ which transforms τ-B₆O to R-B₆O under pure shear deformation. However, under indentation conditions, the lowest stress slip system changes to (001)/⟨110⟩, leading to icosahedra disintegration and hence amorphous band formation.