Showing papers by "Susumu Saito published in 2009"
145 citations
18 citations
TL;DR: In this paper, the authors studied pressure-induced structural phase transition of carbon nanotubes using the constant-pressure tight-binding molecular-dynamics simulation and found that the nanotube bundles transformed into a new phase that consist of graphitic ribbons and diamond blocks, called graphitic nanoribbon solid.
Abstract: We study pressure-induced structural phase transition of carbon nanotubes using the constant-pressure tight-binding molecular-dynamics simulation. The systems studied are nanotube bundles composed of (6,6) armchair nanotube and/or (7,4) chiral nanotube, which are reported to be the nanotubes relatively abundant in experimentally purified sample. We find that the nanotube bundles transforms into a new phase that consist of graphitic ribbons and diamond blocks, “graphitic nanoribbon solid”. It is also found that sp 3-rich phases obtained from the armchair nanotubes possess an anisotropic network and have high hardness which is comparable to that of cubic diamond. In the case of the bundles containing chiral nanotubes, on the other hand, amorphous diamond phase is obtained. Based on the local-density approximation in the density-functional theory, we also investigate the energetics and electronic structure of some of new carbon phases obtained in the molecular-dynamics study.
TL;DR: In this article, the authors performed a systematic study of work functions of 44 kinds of isolated single-walled carbon nanotubes in the framework of the density functional theory and determined the values of work function from the difference between the Fermi level and the vacuum level.
Abstract: The work function is one of the crucial quantities in understanding their field emission properties and applying carbon nanotubes to electronic devices. We perform the systematic study of work functions of 44 kinds of isolated single-walled carbon nanotubes in the framework of the density functional theory. It has been revealed that the first-principles study plays a very important role for predicting various properties of carbon nanotubes. In general, we have to perform the structural relaxation in order to know the accurate electronic properties of carbon nanotubes. Therefore we carry out the complete geometrical relaxations for 44 kinds of carbon nanotubes and evaluate their work functions. The diameters (D) of nanotubes studied satisfy 0.3 < D < 2.0 nm. Especially, we focus on the small diameter carbon nanotubes. We determine the values of work functions from the difference between the Fermi level and the vacuum level. In the semiconducting carbon nanotubes, the Fermi level is chosen at the midgap. As a result, it is found that the carbon nanotubes should be classified into three classes according to the diameter and chiral-angle dependences of work functions.