Defect complexes in carbon and boron nitride nanotubes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (BNNTs) are crucial nanomaterials.
• Understanding defect complexes is vital for tailoring their properties.

Purpose of the Study:

• Investigate the impact of defect complexes on SWCNTs and BNNTs.
• Analyze stability, structural, and electronic property changes.

Main Methods:

• Ab initio pseudopotential density functional theory (DFT).
• Utilized the Castep computational code.
• Examined atomic relaxations and formation energies.

Main Results:

• Atomic relaxations were more pronounced in zig-zag SWCNTs than armchair.
• B(C)B(c) defects induced semimetallic behavior in SWCNTs.
• C(B)B(N) defects rendered BNNTs metallic.
• Zig-zag configurations were energetically favored over armchair in BNNTs.
• Identified preferred defect configurations (C(B)B(N) in B-rich, C(N)N(B) in N-rich environments).
• Determined stable B(N)N(B) defects with significant negative heats of formation.

Conclusions:

• Defect complexes critically influence the electronic and structural properties of nanotubes.
• The type and configuration of defects dictate the resulting material properties (semimetallic/metallic).
• Energetic stability favors zig-zag configurations, especially in BNNTs, with specific defect interactions depending on elemental abundance.