Deformation-Induced Electronic Structure Changes in Boron Nitride Nanotubes

Electronic structures of (6,0), (8,0), and (10,0) single-walled boron nitride nanotubes (SWBNNTs) under tension, torsion and flattening are investigated using first-principles calculations. Energy bands and charge distributions of the SWBNNTs are calculated within the density-functional theory, and forces required to deform the SWBNNTs are estimated from the energy variation with deformation. Our calculations show that the tension, torsion and flattening decrease energy gaps of the SWBNNTs because of a decrease in the energy of the conduction band minimum (CBM). The decrease in the CBM energy is caused by an overlap of CBM charge densities between boron atoms. It is found that the flattening deformation leads to the larger decrease in energy gaps of the SWBNNTs with the smaller force than the tension and torsion.