Quantum Chemical Calculation of the Field Electron Emission Threshold from Short Boron-Nitride Nanotubes

The electronic structure of cylindrical conjugated macromolecules of boron and nitrogen atoms modeling short open nanotubes of zigzag (n,0) and armchair types (n,n) was calculated using density functional theory with the B3LYP hybrid functional in the 6–31G basis set. Their stability as a function of diameter and length was studied. It was shown that a constant electric fi eld applied along the tubes led to a compression of the energy gap in the electron energy spectrum of the nanotubes up to ≈0.2 eV. The threshold of fi eld electron emission from boron-nitride nanotubes was calculated in the framework of the emission molecular orbitals theory. It was shown that, despite conjugated systems of boron-nitride and carbon nanotubes being isoelectronic, substitution of carbon atoms in the nanotube framework of nitrogen and boron atoms led to a decrease in the threshold fi eld strength of the fi eld emission. It was found that the diameter of boron-nitride nanotubes had virtually no eff ect on the emission molecular orbital.