Study Of Vacancy Stabilities In Single-walled Carbon Nanotube

Perfect carbon nanotubes have mechanical, thermal, electrical, chemical andtransport properties, which can be applied into chemical sensors and nanometer electronicdevices. However, there are a variety of structural defects in the production andpreparation processes, such as atomic vacancy defects and Stone-Wales defects. Theexistence of these defects has an important influence on the mechanical, physical andchemical properties of the carbon nanotubes. Therefore the vacancy defect research of thecarbon nanotubes is critical to various properties and application of carbon nanotubes.In this paper related researches are summarized, and on the basis of this, clustermodels are selected using density functional theory method to systematically study thechemical stabilities of single and double vacancy defects in all kinds of carbon nanotubes.Main results are as follows:(1) Based on the direction curvature theory (DCT), we develop its calculationformula, and it is applied to stability prediction of vacancy defects.(2) For the defect product structure of single vacancies, armchair carbon nanotubeshave5-1DB-P and5-1DB-T two kinds of product structure; zigzag carbon nanotubes have5-1DB-T and5-1DB-V two kinds of product structure; helical carbon nanotubes have5-1DB-AP,5-1DB-T and5-1DB-AV three kinds of product structure. For every kind ofproduct structure. The length of the bond are decreasing with the angle of the new C-Cbond with carbon tube axle, the formation of the vacancy structure are more lower. Thestudy of single vacancy defect show that, for each kinds of carbon nanotubes, theformation energy are decreasing with the increasing of the curvature defect K1or the pipediameter. In all the vacancy structures above, the formation energy order is5-1DB-AV>5-1DB-T>5-1DB-AP.(3) The study of double vacancy defects and the formation energy show that, the resultare similar to the single vacancy defect. armchair carbon nanotubes have585-P and585-T two kinds of product structure; zigzag carbon nanotubes have585-T and5-DB-V twokinds of product structure; helical carbon nanotubes have585-AP,585-T and585-AVthree kinds of product structure. For every kind of product structure. The length of thebond are decreasing with the angle of the new C-C bond with carbon tube axle, theformation of the vacancy structure are more lower. The study of double vacancy defectsshow that, for each kinds of carbon nanotubes, the formation energy are decreasing withthe increasing of the curvature defectK2. In all the vacancy structures above, the formationenergy order is585-AV>585-T>585-AP. No matter what kinds of defect structure orthe type of carbon nanotubes, the formation energy of both the singe and double vacancydefects are decreasing with the curvature defect K1or K2.