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Energetics, structure, mechanical and vibrational properties of single-walled carbon nanotubes

Gao, Guanghua and Çağin, Tahir and Goddard, William A., III (1998) Energetics, structure, mechanical and vibrational properties of single-walled carbon nanotubes. Nanotechnology, 9 (3). pp. 184-191. ISSN 0957-4484. http://resolver.caltech.edu/CaltechAUTHORS:GAOnanotech98

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Abstract

In this paper, we present extensive molecular mechanics and molecular dynamics studies on the energy, structure, mechanical and vibrational properties of single-wall carbon nanotubes. In our study we employed an accurate interaction potential derived from quantum mechanics. We explored the stability domains of circular and collapsed cross section structures of armchair (n,n), zigzag(n,0) , and chiral (2n,n) isolated single-walled carbon nanotubes (SWNTs) up to a circular cross section radius of 170 Å. We have found three different stability regions based on circular cross section radius. Below 10 Å radius only the circular cross section tubules are stable. Between 10 and 30 Å both circular and collapsed forms are possible, however, the circular cross section SWNTs are energetically favorable. Beyond 30 Å (crossover radius) the collapsed form becomes favorable for all three types of SWNTs. We report the behavior of the SWNTs with radii close to the crossover radius ((45, 45), (80, 0), (70, 35)) under uniaxial compressive and tensile loads. Using classical thin-plane approximation and variation of strain energy as a function of curvature, we calculated the bending modulus of the SWNTs. The calculated bending moduli are [kappa][sub](n,n)=963.44 GPa, [kappa][sub](n,0)=911.64 GPa, and [kappa][sub](2n,n)=935.48 GPa. We also calculated the interlayer spacing between the opposite sides of the tubes and found d[sub](n,n)= 3.38 angstroms, d[sub](2n,n)= 3.39 angstroms, and d[sub](n,0)= 3.41 angstroms. Using an enthalpy optimization method, we have determined the crystal structure and Young's modulus of (10,10) armchair, (17,0) zigzag and (12, 6) chiral forms (which have similar diameter as (10,10)). They all pack in a triangular pattern in two dimensions. Calculated lattice parameters are a[sub](10,10)= 16.78 angstroms, a[sub](17,0)= 16.52 angstroms and a[sub](12,6)= 16.52 angstroms. Using the second derivatives of potential we calculated Young's modulus along the tube axis and found Y[sub](10,10)=640.30 GPa, Y[sub](17,0)=648.43 GPa, and Y[sub](12,6)=673.94 GPa. Using the optimized structures of (10,10), (12,6) and (17,0), we determined the vibrational modes and frequencies. Here, we report the highest in-plane mode, compression mode, breathing mode, shearing mode and relevant cyclop mode frequencies.


Item Type:Article
Additional Information:© 1998 IOP Publishing Ltd. Received 6 January 1998, Print publication: Issue 3 (September 1998). This research was funded by NASA (computational nanotechnology) and by NSF-GCAG (ASC 92-100368). The facilities of the MSC are also supported by grants from NSF (CHE 95-22179), DOE-ASCI, ARO/DURIP, BP Chemical, ARO-MURI, Exxon, Seiko-Epson, Asahi Chemical, Beckman Institute, Chevron Petroleum Technology Co., Chevron Chemical Co., NASA/JPL, ONR, Avery Dennison, and Chevron Research Technology Co.
Record Number:CaltechAUTHORS:GAOnanotech98
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:GAOnanotech98
Alternative URL:http://dx.doi.org/10.1088/0957-4484/9/3/007
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:521
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:12 Jul 2005
Last Modified:26 Dec 2012 08:40

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