Transverse dielectric properties of boron nitride nanotubes by ab initio electric field calculations

Extensive ab initio finite electric-field calculations are performed to study the static transverse dielectric properties of boron nitride nanotubes via the sawtooth potential approach. It is shown that the transverse polarizability is proportional to the tube radius rather than to the square of it, and that the screening factor is not a constant but decreases monotonically with increasing tube radius. A classical cylindrical dielectric shell model, with a dielectric constant of 5.90 and an effective shell thickness of 2.50 A, is shown to reproduce very well the ab initio results for both single- and multiwalled boron nitride nanotubes.