▎ 摘　　要

The energy band gap of graphene, h-boron nitride, stanene, silicene, germanene, and phosphorene nanoribbons is investigated theoretically with two approaches. In the first approach, a set of equations to calculate the energy band gap of nanoribbons is deduced using the expression of Fermi velocity. The size dependency of the energy band gap so obtained confirms previous expressions. The second approach, however, determines resistivity by directly connecting quantity to the energy band gap using an electron-acoustical phonon scattering mechanism. For the calculation of the energy band gap and resistivity, the armchair configuration of nanoribbons is considered. It is observed that the transverse magnetic field influences the energy band gap and resistivity. The magnitude of the band gap is negative up to a certain value of the field and turns positive at a sufficiently higher field. The negative band gap can be interpreted as metallic behavior of the materials. The results of the work are useful in the determination of the energy band gap of nanoribbons for their nanoelectronic and optoelectronic applications as well as tuning the band gap using the applied magnetic field.