Abstract Resourceful beyond-graphene two-dimensional (2D) carbon crystals have been proposed/synthesized; however, the fundamental knowledge of their melting thermodynamics remains lacking. Here, the structural and thermodynamic properties of nine contemporary 2D carbon crystals upon heating are investigated using first-principle-based ReaxFF molecular dynamics simulations. Those 2D carbon crystals show distinct evolution of energetic and Lindemann index that distinguish their thermal stabilities. There are two or three critical temperatures at which structural transformation occurs for non-hexagon-contained 2D carbon allotropes. Analysis of polygons reveals that non-hexagon-contained 2D carbon crystals show thermally induced hex-graphene transitions via mechanisms such as bond rotations, dissociation, and reformation of bonds. The study provides new insights into the thermodynamics and pyrolysis chemistry of 2D carbon materials, as well as structural transitions, which is of great importance in the synthesis and application of 2D materials in high-temperature processing and environment.

中文翻译：

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二维碳晶体中的热诱导六方石墨烯跃迁

摘要 已经提出/合成了资源丰富的超石墨烯二维（2D）碳晶体；然而，关于它们的熔化热力学的基本知识仍然缺乏。在这里，使用基于第一原理的 ReaxFF 分子动力学模拟研究了九种当代二维碳晶体在加热时的结构和热力学性质。这些二维碳晶体显示出能量和林德曼指数的明显演变，从而区分了它们的热稳定性。对于非六边形包含的二维碳同素异形体，有两个或三个临界温度发生结构转变。对多边形的分析表明，不含六边形的二维碳晶体通过键旋转、解离和键的重组等机制显示出热诱导的六边形石墨烯转变。