Graphdiyne is formed by two acetylene bonds conjugatively connecting two phenyl rings, which then extend to a sizable two-dimensional structure. In this work, a molecular size-dependent C≡C stretching vibrational transition intensity is predicted by density functional theory in graphdiyne; in particular, the strongest infrared-active transition is enhanced in intensity by a factor of as high as 2190 from phenyl-acetylenic dimer to graphdiynic 46-mer, showing ca. 300 times enhancement per acetylene bond on average, examined at the level of B3LYP/6-31G*. Such an enhancement of vibrational transition intensity is caused by intramolecular electronic delocalization that gives rise to an enlarged transition dipole moment as well as by intramolecular vibrational delocalization that gives rise to intensity borrowing in such two-dimensionally conjugated graphdiyne molecular sheets. The enhancement is found to be diminished in defected graphdiynes. The results suggest that the periodically appearing C≡C bond may be used as a vibrational spectroscopic marker for assessing the size of perfect graphdiyne oligomers, and the characteristic C≡C stretching absorption can potentially be used to differentiate perfect graphdiyne sheets from defected ones.

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二维Graphdiyne片的振动表征

Graphdiyne由两个连接两个苯环的乙炔键形成，然后延伸到相当大的二维结构。在这项工作中，通过密度泛函理论在石墨二炔中预测了分子尺寸依赖性的C≡C拉伸振动跃迁强度。特别是，最强的红外活性跃迁的强度从苯乙炔二聚体到石墨二炔46-mer的强度提高了2190倍，显示出 在B3LYP / 6-31G *水平下，每个乙炔键平均增强300倍。振动跃迁强度的这种提高是由分子内电子离域化引起的，该分子离域化引起了增大的跃迁偶极矩，以及分子内振动离域化引起了这种二维共轭石墨二炔分子片材中强度的借用。发现该增强在有缺陷的石墨二炔中被减弱。结果表明，周期性出现的C≡C键可以用作振动光谱标记，以评估完美的石墨二炔低聚物的尺寸，并且特征性的C potentiallyC拉伸吸收可以潜在地用于区分完美的石墨二炔薄板和有缺陷的石墨二炔薄板。