Theoretical investigation of the electric responses of the (4,0) zigzag model of singlewalled boron nitride nanotube (BNNT) with lengths 10, 12, 14 and 16 ˚A, has been performed with density functional theory calculation by considering the influence from the external electric field (EF) with strengths 0−1.6 × 10−2 a.u. using B3LYP/6-31G∗ method. Results show that in both cases, with increase in the length of BNNT and the EF strength, there is a decrease the HOMO-LUMO gap (HLG) values and increase in the electric dipole moment. Natural bond orbital (NBO) atomic charge analysis shows that increasing the EF intensity increases separation of the positive and the negative center of electric charges of BNNT molecule. Results of this study demonstrate that the molecular scale device formed by BNNTs can be significantly influenced by the length of the BNNT itself and the external EF intensity.
