Ab initio calculations of electron affinity and ionization potential of carbon nanotubes

TL;DR

This study uses ab initio methods to calculate the electron affinity and ionization potential of specific single-wall carbon nanotubes, analyzing effects of size, termination, and packing on their electronic properties.

Contribution

It provides detailed ab initio calculations of EA and IP for (5,5) and (7,0) nanotubes, including finite-size, termination, and packing effects, which were not comprehensively studied before.

Findings

EA and IP depend on nanotube length and termination.

Finite-size effects cause slow convergence of electronic properties.

Packing in arrays influences electronic characteristics.

Abstract

By combining ab initio all-electron localized orbital and pseudopotential plane-wave approaches we report on calculations of the electron affinity (EA) and the ionization potential (IP) of (5, 5) and (7, 0) single-wall carbon nanotubes. The role played by finite-size effects and nanotube termination has been analysed by comparing several hydrogen-passivated and not passivated nanotube segments. The dependence of the EA and IP on both the quantum confinement effect, due to the nanotube finite length, and the charge accumulation on the edges, is studied in detail. Also, the EA and IP are compared to the energies of the lowest unoccupied and highest occupied states, respectively, upon increasing the nanotube length. We report a slow convergence with respect to the number of atoms. The effect of nanotube packing in arrays on the electronic properties is eventually elucidated as a function of the intertube distance.