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arXiv 1107.5299cond-mat.mes-hall
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两个石墨烯碎片系统中层间相互作用的性质

On the nature of interlayer interactions in a system of two graphene fragments

Julia Berashevich, Tapash Chakraborty

摘要:

借助量子化学方法,我们研究了不同堆叠排列(AA和AB)的石墨烯片段之间的层间相互作用的性质。我们发现,作为系统基态的AB堆积模式的特征在于几乎不存在于AA中的有效带间轨道相互作用。它们的消失引起石墨烯层之间的电子去耦,使得当堆叠图案从AB变为AA时,薄片之间的键合相互作用$ΔE_{oi}$从-0.482 eV急剧降低到-0.087 eV。提高保持相同AA晶格有序的层之间的成键相互作用的有效方法是诱导层的旋转。随着薄片的旋转,键合相互作用得到改善,主要是由于抑制泡利排斥,这反过来又增加了层间轨道相互作用,而带间部分的那些仍然可以忽略不计的整个范围内的旋转角。泡利斥力也被发现是主要的力量分开的两个片段的堆叠模式从AA到AB的变化。这提高了平衡层间距离,AA堆叠的平衡层间距离大于AB堆叠的既定值(3.4 A)。

英文摘要:

With the help of the quantum chemistry methods we have investigated the nature of interlayer interactions between graphene fragments in different stacking arrangements (AA and AB). We found that the AB stacking pattern as the ground state of the system, is characterized by the effective inter-band orbital interactions which are barely present in the AA. Their vanishing induces electronic decoupling between the graphene layers, so that the bonding interaction $ΔE_{oi}$ between the flakes is drastically reduced from -0.482 eV to -0.087 eV as the stacking pattern is changed from AB to AA. The effective way to improve the bonding interaction between layers preserving the same AA lattice order is to induce rotation of the layer. As the flake is rotated, the bonding interactions are improved mostly due to suppression of the Pauli repulsion which in turn increases the interlayer orbital interactions, while the inter-band part of those remain negligible on the whole range of the rotation angle. The Pauli repulsion is also found to be the main force moving apart two fragments as the stacking pattern is changed from AA to AB. This enhances the equilibrium interlayer distance, which for the AA staking is larger than the established value for the AB stacking (3.4 A)

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