Bandgap closure of a flattened semiconductor carbon nanotube: A first-principles study

We investigate, through first-principles calculations, the effects of a flattening distortion on the electronic properties of a semiconductor carbon nanotube. The flattening causes a progressive reduction of the band gap from 0.92 eV to zero. The band-overlap insulator-metal transition occurs for an interlayer distance of 4.6 Å. Supposing that the flattening of the nanotube can be produced by a force applied by a scanning microscope tip, we estimate that the force per unit length of the nanotube that is necessary to reach the insulator-metal transition is 7.4 N/m.