Electronic properties of boron nanotubes with axial strain

The electronic properties of boron nanotubes with axial strain are investigated by first principle calculations. The band gaps of the (3, 3) and (5, 0) boron nanotubes are found to be modified by axial strain significantly. We find that the semiconductor-metal transition occurs for the (3, 3) boron nanotubes with both compressive and tensile strain. While for the (5, 0) boron nanotubes, only the tensile strain induces the semiconductor-metal transition. These boron nanotubes have the largest gaps under compressive strain.