Effect of carbon monovacancy on the adsorption of MgH2 on the (8,0) and (8,8) SWCNT

Abstract

The adsorption of magnesium hydride (MgH2) is studied by Density Functional Theory (DFT) on (8,0) and (8,8) single-walled carbon nanotubes (SWCNT) containing a vacancy. In the case of (8,0), the adsorption geometry is a top site and perpendicular to the tube direction (TO2 = − 0.062 eV) and for (8,8) is in a hollow site, parallel to the tube (H2O1 = − 0.253 eV). The H–Mg–H angle is distorted to 161◦ when adsorbed on (8,8). The closest C–Mg distances are 3.482 Å and 3.758 Å for the defective (8,0) and (8,8), respectively. The (8,8) SWCNT exhibits a magnetization of about 1 μB. After adsorption on (8,0) SWCNT, the Eg is reduced from 0.574 eV to 0.390 eV, while for the defective CNT, the change is from 0.355 eV to 0.095 eV. The electronic structure (DOS) shows a stabilization of the atomic states of both Mg and H at lower energies.