Recent experiments reported a substantial toughening of nanotwinned diamond (nt-diamond) composite with coherently interfaced diamond polytypes (different stacking sequences). This discovery emphasizes the diversity of graphite-like structures in carbon onion precursors for synthesizing nt-diamond composite. We designed five new graphitic polytypes to investigate structural diversity in graphitic systems. Under ambient pressure, the energies of all the proposed polytypes are between those of graphite (AB structure) and a previously predicted AA structure. Dynamic and elastic stability results showed that four structures (AB'C', AB'D', AAB and ABCB) can be stable under ambient pressure. These four structures all have a large interlayer distance comparable to those in carbon onion and turbostratic graphite. Chiral graphitic structures (AB'D' and AB'C') with reversible electrical properties under slight stress might be responsible for the controversy about the bandgap of graphitic samples. Therefore, these four structures are most likely to be a part of the structures existing in carbon onion and turbostratic graphite or are structural defects in graphitic samples.

中文翻译：

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石墨系统的结构多样性、大层间距和可切换的电子特性

最近的实验报告了纳米孪晶金刚石（nt-金刚石）复合材料与相干界面金刚石多型（不同的堆叠序列）的显着增韧。这一发现强调了用于合成 nt-金刚石复合材料的碳洋葱前体中类石墨结构的多样性。我们设计了五种新的石墨多型来研究石墨系统中的结构多样性。在环境压力下，所有提议的多型体的能量介于石墨（AB 结构）和先前预测的 AA 结构之间。动态和弹性稳定性结果表明，四种结构（AB'C'、AB'D'、AAB 和 ABCB）在环境压力下可以保持稳定。这四种结构都具有可与碳洋葱和乱层石墨相媲美的大层间距。在轻微应力下具有可逆电性能的手性石墨结构（AB'D' 和 AB'C'）可能是导致石墨样品带隙争议的原因。因此，这四种结构最有可能是洋葱和乱层石墨中存在的结构的一部分，或者是石墨样品中的结构缺陷。