Nucleation mechanism for the direct graphite-to-diamond phase transition
Nucleation mechanism for the direct graphite-to-diamond phase transition
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DOI：
10.1038/nmat3078
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发表时间：
2011-09-01
期刊：
影响因子：
41.2
通讯作者：
Parrinello, Michele
中科院分区：
文献类型：
--
作者：
Khaliullin, Rustam Z.;Eshet, Hagai;Parrinello, Michele
石墨和金刚石具有相当的自由能，但是在没有催化剂的情况下由石墨形成金刚石需要的压力显著高于平衡共存时的压力（1-7）。在较低的温度下，金刚石的亚稳六方多晶型物的形成是有利的，而不是更稳定的立方金刚石（2，5 -7）。这些现象不能用以前的理论研究（8-12）中提出的协调机制来解释。使用从头算质量的神经网络势（13），我们进行了一个大规模的石墨到金刚石转变的研究，假设它通过成核发生。成核机制解释了所观察到的现象，并揭示了其微观起源。我们证明，伴随着金刚石核的形成的大的晶格畸变抑制在低压下的相变，并在较高的压力下将其导向六方金刚石相。提出的成核机制应该提高我们的理解，在广泛的碳基材料的结构转变。
Graphite and diamond have comparable free energies, yet forming diamond from graphite in the absence of a catalyst requires pressures that are significantly higher than those at equilibrium coexistence(1-7). At lower temperatures, the formation of the metastable hexagonal polymorph of diamond is favoured instead of the more stable cubic diamond(2,5-7). These phenomena cannot be explained by the concerted mechanism suggested in previous theoretical studies(8-12). Using an ab initio quality neural-network potential(13), we carried out a large-scale study of the graphite-to-diamond transition assuming that it occurs through nucleation. The nucleation mechanism accounts for the observed phenomenology and reveals its microscopic origins. We demonstrate that the large lattice distortions that accompany the formation of diamond nuclei inhibit the phase transition at low pressure, and direct it towards the hexagonal diamond phase at higher pressure. The proposed nucleation mechanism should improve our understanding of structural transformations in a wide range of carbon-based materials.