Electronic structure and optical properties of boron nitride nanotube bundles from first principles

• We investigated the electronic and optical properties of armchair and zigzag BNNT bundles.
• Effects of intertube coupling on the electronic dispersions of BNNT bundles are demonstrated.
• Bundling causes broadening, small shifts and increasing of dielectric functions peak positions.

The electronic and optical properties of bundled armchair and zigzag boron nitride nanotubes (BNNTs) are investigated by using density functional theory. Owing to the inter-tube coupling, the dispersions along the tube axis and in the plane perpendicular to the tube axis of BNNT bundles are significantly varied, which are characterized by the decrease of band gap, the splitting of the doubly degenerated states, the expansions of valence and conduction bands. The calculated dielectric functions of the armchair and zigzag bundles are similar to that of the isolated tubes, except for the appearance of broadened peaks, small shifts of peak positions about 0.1 eV and increasing of peak intensities.