Control of Electric Dipole Moment using Deformation induced by Functionalization of (5, 0) Zigzag Carbon Nanotubes as Gigahertz Oscillators

Siroos Rastani,Hossein Mostaanzadeh

doi:10.17159/0379-4350/2019/v72a29

Abstract

Electric dipole moment (EDM) required for the relative motion of carbon nanotube (CNT) walls in nanoelectromechanical systems (NEMS) such as actuators and oscillators is studied by functionalization. Pristine (5,0) zigzag carbon nanotube with little inherent electric dipole moment (ì) were deformed by adding three -OH functional groups to its end rims. The properties of eight yielded isomers are studied. The Gibbs free energy calculations demonstrate that the eight structures are more stable than pristine CNT. The induced deformation resulted in charge imbalances which developed large electric dipole moments for each case. The values of dipole moments produced for all cases are calculated. The bandgap energy, conductivity, density of state (DOS) and IR spectra of these structures are also computed and analyzed. The study revealed that the location of the -OH positioning (site selectivity) which gives rise to different degrees of deformation has a significant impact on all of the above parameters, especially the magnitude and direction of the electric dipole moment. The functionalization produced large ì of about 6.9 D for 60 carbon atoms nanotube which is higher than in the previous study. Applying an external electric field to the isomers causes the CNTs with large dipole moments to either get attracted or repelled and hence physical movement or oscillation of the nanotube occurs. The frequency of this oscillation is in gigahertz scale. Keywords: Gigahertz oscillator, electric dipole moment, deformation, carbon nanotube, hydroxyl functionalization, site selectivity.

Highlights

With the advent of carbon nanotubes (CNTs) special structural, electronic, and optical devices along with many potential applications are being introduced to scientists and engineers.[1,2,3,4,5] One-dimensional single-wall carbon nanotubes (SWCNT) for example, are employed in new composites, molecular electronics,[6,7] optics,[8] sensors,[9] nanomechanics[10] and catalysts.[11]
The electric dipole moment magnitude and direction for eight isomers resulting from end functionalization of CNTs with three –OH groups are calculated
Calculations show that the molecular properties such as geometry, stability, vibrational frequency and electrical aspects of the resulted hydroxylated CNTs strongly depend on the position of -OH groups

Summary

Introduction

With the advent of carbon nanotubes (CNTs) special structural, electronic, and optical devices along with many potential applications are being introduced to scientists and engineers.[1,2,3,4,5] One-dimensional single-wall carbon nanotubes (SWCNT) for example, are employed in new composites, molecular electronics,[6,7] optics,[8] sensors,[9] nanomechanics[10] and catalysts.[11]. Zigzag SWCNTs are deformed by end functionalization (adding 3 –OH groups to the end rims rather than the body of the nanotube) and the resulting deformation as well as magnitude and direction of electric dipole moment for each case is calculated.

Results

Conclusion