STABILITY AND BAND-GAP CONSTANCY OF BORON-NITRIDE NANOTUBES

Extensive LDA and quasi-particle calculations have been performed on b oron nitride (BN) single-wall and multi-wall nanotubes. Strain energie s are found to be smaller for BN nanotubes than for carbon nanotubes o f the same radius, owing to a buckling effect which stabilizes the BN tubular structure. For tubes larger than 9.5 angstrom in diameter, the lowest conduction band is predicted to be free-electron-like with ele ctronic charge density localized inside the tube. For these tubes, thi s band is at constant energy above the top of the valence band. Conseq uently, contrarily to carbon nanotubes, single- and multi-wall BN nano tubes are constant-band-gap materials, independent of their radius and helicity. In addition, we expect them to exhibit remarkable propertie s under n-type doping.