Structural and phonon properties of bundled single- and double-wall carbon nanotubes under pressure
Structural and phonon properties of bundled single- and double-wall carbon nanotubes under pressure
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DOI：
10.1021/jp3093176
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
A. L. Aguiar;R. Capaz;A. G. S. Filho;Alfonso San-Miguel
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文献类型：
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作者：
A. L. Aguiar;R. Capaz;A. G. S. Filho;Alfonso San-Miguel
在这项工作中，我们报告了在静水压力下成束单壁和双壁碳纳米管（DWNT）的结构和声子特性的理论耦合研究。我们的结果证实了高压状态下单壁碳纳米管体积的巨大变化，这是由从圆形相到塌陷相的相变所决定的，这严格取决于管直径。对于 DWNT，这些结果首先显示外管转变为多边形，随后在内管椭圆化开始时外管和内管同时塌陷。在 DWNT 塌陷之前，声子计算再现了实验观察到的 RBM 和切向 G$_z$ 模式对内管压力引起的蓝移的屏蔽效应。此外，碳纳米管束的塌陷会引起切向分量的突然红移，这与实验研究一致。 SWNT 塌陷管的 G$_z$ 带分析表明，管的扁平区域位于其 G 带信号的起源处。这解释了在塌陷相中观察到的 G 带的石墨型压力演化，并另外提供了识别塌陷管的方法
In this work, we report a theoretical coupled study of the structural and phonons properties of bundled single- and double-walled carbon nanotubes (DWNTs), under hydrostatic compression. Our results confirm drastic changes in volume of SWNTs in high-pressure regime as assigned by a phase transition from circular to collapsed phase which are strictly dependent on the tube diameter. For the DWNTs, those results show first a transformation to a polygonized shape of the outer tube and subsequently the simultaneous collapse of the outter and inner tube, at the onset of the inner tube ovalization. Before the DWNT collapse, phonon calculations reproduce the experimentally observed screening effect on the inner tube pressure induced blue shift both for RBM and tangential G$_z$ modes . Furthermore, the collapse of CNTs bundles induces a sudden redshift of tangential component in agreement with experimental studies. The G$_z$ band analysis of the SWNT collapsed tubes shows that the flattened regions of the tubes are at the origin of their G-band signal. This explains the observed graphite type pressure evolution of the G band in the collapsed phase and provides in addition a mean for the identification of collapsed tubes