Electronic structures of boron nitride nanotubes subjected to tension, torsion, and flattening: A first-principles DFT study

Electronic structures of (6,0), (8,0), and (10,0) single-walled boron nitride nanotubes (SWBNNTs) subjected to 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 using energy variation with deformation. Our calculations show that all the deformation modes decrease the energy gaps of the SWBNNTs because of a decrease in the conduction-band minimum (CBM) energy, which is caused by an overlap of CBM charge densities between circumferentially neighboring boron atoms. It is found that flattening with a force smaller than that applied for tension or torsion causes a larger decrease in energy gaps of the SWBNNTs and that the force required for flattening SWBNNTs is not unrealistic.