Ab-initio investigation of structural, electronic, and optical properties of (5,0) finite-length carbon nanotube

TL;DR

This study uses density functional theory to analyze how size influences the structural, electronic, magnetic, and optical properties of finite (5,0) carbon nanotubes, revealing convergence at 30 Å and edge effects in excited states.

Contribution

It provides a comprehensive ab-initio analysis of finite (5,0) carbon nanotubes, highlighting size-dependent convergence, edge effects, and magnetic properties, which were not previously detailed.

Findings

Structural and electronic properties converge at ~30 Å.

Edge effects dominate magnetic and optical responses.

Identification of a magic size at ~15 Å.

Abstract

We use density functional computations to study the size effects on the structural, electronic, magnetic, and optical properties of (5,0) finite carbon nanotubes (FCNT), with length in the range of 4-44 \AA. It is found that the structural and electronic properties of (5,0) FCNTs, in the ground state, converge at a length of about 30 \AA, while the excited state properties exhibit long-range edge effects. We discuss that curvature effects govern the electronic structure of short (5,0) FCNTs and enhance energy gap of these systems, in contrast to the known trend in the periodic limit. It is seen that compensation of curvature effects in two special small sizes, may give rise to spontaneous magnetization. The obtained cohesive energies provide some insights into the effects of environment on the growth of FCNTs. The second-order difference of the total energies reveals an important magic size of about 15 \AA. The optical and dynamical magnetic responses of the FCNTs to polarized electromagnetic pulses are studied by time dependent density functional theory. The obtained results show that the static and dynamic magnetic properties mainly come from the edge carbon atoms. The optical absorption properties are described in term of local field effects and characterized by Casida linear response calculations.