Chirality-dependent properties of carbon nanotubes: electronic structure, optical dispersion properties, Hamaker coefficients and van der Waals–London dispersion interactions

Abstract

Optical dispersion spectra at energies up to 30 eV play a vital role in understanding the chirality-dependent van der Waals London dispersion interactions of single wall carbon nanotubes (SWCNTs). We use one-electron theory based calculations to obtain the band structures and the frequency dependent dielectric response function from 0-30 eV for 64 SWCNTs differing in radius, electronic structure classification, and geometry. The resulting optical dispersion properties can be categorized over three distinct energy intervals (M, π, and σ, respectively representing 0-0.1, 0.1-5, and 5-30 eV regions) and over radii above or below the zone-folding limit of 0.7 nm. While π peaks vary systematically with radius for a given electronic structure type, σ peaks are independent of tube radius above the zone folding limit and depend entirely on SWCNT geometry. We also observe the so-called metal paradox, where a SWCNT has a metallic band structure and continuous density of states through the Fermi level but still behaves optically like a material with a large optical band gap between M and π regions. This paradox appears to be unique to armchair and large diameter zigzag nanotubes. Based on these calculated one-electron dielectric response functions we compute and review Van der Waals -London dispersion spectra, full spectral Hamaker coefficients, and van der Waals -London dispersion interaction energies for all calculated frequency dependent dielectric response functions. Our results are categorized using a new optical dielectric function classification scheme that groups the nanotubes according to observable trends and notable features (e.g. the metal paradox ) in the 0-30 eV part of the optical dispersion spectra. While the trends in these spectra begin to break down at the zone folding diameter limit, the trends in the related van der Waals -London dispersion spectra tend to remain stable all the way down to the smallest single wall carbon nanotubes in a given class. IntroductionSince their discovery in 1993 by the Iijima and the Bethune groups 1,2 , single wall carbon nanotubes (SWCNTs) have received enthusiastic attention. Their intriguing mechanical and electrical properties make them ideal for a wide range of applications, from metal oxide semiconductor field effect transistors (MOSFETs) to novel drug delivery systems 3-8 and have inspired strong scientific and industrial interest 1,[9][10][11][12][13][14][15] . The area that has arguably received the most attention and focus is † Electronic Supplementary Information (ESI) available: [details of any supplementary information available should be included here]. See ) * In the context of the dielectric response functions of CNTs, we denote the SWCNT with a mnemonic [n,m, type] rather then the standard but equivalent (n,m), when we want to invoke its type explicitly in order to help the reader organize the voluminous information and in order to be consistent with our previous publications. Of course the two designations, together with the simple (n-m)/3 = integer rule to...

van der Waals Interactions on the Mesoscale: Open-Science Implementation, Anisotropy, Retardation, and Solvent Effects

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“…17 This formulation vastly improves upon previous isotropic 17 and nonretarded 8 results. We apply it to a range of technologically promising cylindrical materials, including metallic and semiconducting SWCNTs, 8,[21][22][23][24] multiple composites of DNA, [25][26][27] collagen, 28 polystyrene, 29 and inorganic materials. Our results are presented as Hamaker coefficients, forces, and torques 30 for a wide range of symmetric (identical materials interacting across an isotropic medium) and asymmetric (different materials interacting across an isotropic medium) interaction geometries in aqueous media.…”

Third-Nearest-Neighbors Tight-Binding Description of Optical Response of Carbon Nanotubes: Effects of Chirality and Diameter

“…In the infrared range, the optical spectra display a strong dependence on the radius which is in agreement with a previous study. 37 In this energy region, the optical spectra for non-armchair metallic CNTs have two distinct peaks that show red shift by increasing the diameter and chiral angle. For the larger radius and chiral angle, their energy separation becomes smaller and finally converts to a single peak for armchair CNTs (Fig.…”

Computational Study of a Heterostructural Model of Type I Collagen and Implementation of an Amino Acid Potential Method Applicable to Large Proteins

“…Such calculations will provide the dielectric response function which, so far, is only approximated by using the polarizable continuum model (PCM) [90,91]. The dielectric response function can be used as an input for the calculation of long-range van der Waals interactions between proteins in aqueous solution along the similar lines as recently successfully implemented for the single walled carbon nano-tubes of different chirality [92]. We believe that such an endeavor, which is now well within our current computational capability, can push collagen research to a much higher level of accuracy and sophistication.…”