In the phase diagram of elemental boron, an unknown high-pressure form was identified as γ-orthorhombic boron (γ-B₂₈), provoking studies of the extraordinary properties of its main building blocks, B₁₂ icosahedra and B₂ dumbbells. Although two low-pressure phases, α- and β-rhombohedral boron (α-B₁₂ and β-B₁₀₆), are also composed of icosahedra, the detailed kinetics and mechanisms of the structural transition from α-B₁₂ or β-B₁₀₆ to γ-B₂₈ remain poorly understood. We report on new metastable boron phases formed during the transition in high-pressure high-temperature conditions that were discovered using the crystal structure search method. The metastable phases are understood to be a three-dimensional buckled defective honeycomb lattice in which boron vacancies lead to a dynamically and mechanically stable structure with triangular motifs. We suggest that the metastable phases act as intermediate states on the transition pathway from α-B₁₂ to γ-B₂₈ owing to their structural flexibility and low enthalpies, in the framework of Ostwald’s step rule.

在元素硼的相图中，未知的高压形式被鉴定为γ-斜方硼（γ- _B28），从而引发了对其主要结构块B ₁₂二十面体和B ₂哑铃的非凡性能的研究。虽然两个低压阶段，α-和β-菱形硼（α-B ₁₂和β-B ₁₀₆），也由二十面体的，由α-B的详细动力学和结构转换的机制₁₂或β-B ₁₀₆至γ- _B28仍然知之甚少。我们报告了在高压高温条件下使用晶体结构搜索方法发现的过渡过程中形成的新的亚稳硼相。亚稳相被理解为三维屈曲缺陷蜂窝状晶格，其中硼空位导致具有三角形图案的动态和机械稳定结构。我们建议，亚稳相充当从α-B的过渡路径的中间状态₁₂到γ-B ₂₈由于其结构的灵活性和低焓，在奥氏步骤规则的框架内。