In the case of SWCNT we can apply electric field along axial direction and transverse direction. We are interested in the field direction applied perpendicular to the tube axis (transverse direction). The field strength is denoted as ‘E’. Initially, we started along x-direction with E = 0.5 V/Å (0.01 a. u.). The SWCNT-H is relaxed under this field strength. We repeated the calculations with the same value of electric field along y-direction. There is no significant change in the total energy and the geometrical structure between the two calculations. Therefore further computations are carried out with electric field applied along x-direction. Later on E is increased to 1 V/Å and incremented with a value of 1 V/Å. The structural relaxations are carried out in the presence of electric field. The chemisorption of H on CNT causes charge redistribution such that a small bond dipole forms on C–H bond (Cδ−−Hδ+) because of the different electronegativity of H and C atoms. The bader charge analysis reveals that there is +0.0338 net charge on H atom and −0.0338 net charge on C atom [59]. In addition, the C–H bonds are covalent and highly directional. Therefore the SWCNT-H gets easily polarized under external electric field.