Mechanical, Electronic and thermal properties of ultrathin tungsten nanowires and nanotubes

• Main Authors: Jia-yun Li, 李嘉芸
• Other Authors: Shin-Pon Ju
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/3ewyw8

碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 102 === In this study, the structures of ultrathin W nanowires and nanotubes were predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding potential. The mechanical properities and thermal stability of the W nanowires and nanotubes were further examined by the molecular dynamic (MD) calculation and density functional theory molecular dynamics (DFT-MD) simulation. Furthermore, the oxidation of CO molecules on W helical nanotube has also been investigated by DFT calculations. The mechanical properties results of nanowires and nanotubes are presented that W nanowires and nanotubes possess good ductility and their Young''s moduli decrease with decreasing of size. In terms of thermal stability, these W nanowires are still stable at temperatures as high as 1300 K. In the electronic properties, we analyze the PDOS of W nanowires and nanotubes with different sizes to understand orbital hybridization. The results show that one-dimension W nanostructures possess better charge transfer capabilities than bulk W, and the W helical nanotube has the best chemical activity in six structures. Therefore, Eley-Radeal (ER) mechanism is considered for examining and comparing the mechanism of CO oxidation on W helical nanotube and W (111) surface. Then the PDOS of the CO oxidation were analyzed to understand the interaction between W nanotube and adsorbed molecules. The calculations show that the energy barrier for W nanotubes is only 0.468 eV, lower than W(111) surface, this result means that W nanotubes have good catalytic activity which can be replaced other structures as catalysts.