Electronic structures of deformed B2C nanotubes under tensile strain

The vibrational properties and the band gaps of new B2C nanotubes have been studied by the first principles calculations. It is found that (1) there is a typical Raman-active radial-breathing vibrational mode (RBM), which is similar to that of carbon nanotubes. The RBM frequency decreases in a linear proportion to the inverse diameter, whose variation slope depends on the types of B2C nanotubes. (2) Under an applied tensile strain, the band gap of B2C tubes is found to change greatly. For example, their band gaps can decrease to zero with increasing tensile strain for the (n, 0) B2C tubes with odd n, showing clearly a metal–insulator transition, which cannot happen for the (n, 0) B2C tubes with even n and the (0, n) B2C tubes.