First-Principle Investigation of The Alkali Metal Interactions With MgO Armchair -Nanotubes

Abstract

Encapsulation inside and adsorption of Lithium alkali metals (Li) on the surface of magnesium oxide armchair - nanotubes (MgONTs) with different diameters (3×3, 4×3, 5×3, 6×3, 7×3 and 8×3) was investigated by using density functional theory. According to the obtained results, the adsorption on the oxygen site of tube surfaces with adsorption energies with energies in the range of −0.93 to −1.11 eV are most stable than the encapsulation complexes in the range of −0.51 to −0.99 eV. Energy gap (Eg) of the nanotubes dramatically decreases upon the encapsulation / adsorption of the alkali metal, resulting in enhancement of their electrical conductivity. The order of energy gap decrement caused by the metal encapsulation / adsorption is as follows: adsorption > encapsulation. Li - MgONTs are photoactives and they have high values of oscillator strengths. The results suggest that the MgONTs were transformed from semi – insulator to semiconductor upon the alkali metal encapsulation / adsorption. Increasing the tube diameter, the adsorption energies of the MgONT-Li complexes are stable and the encapsulation energies of the alkali metal are decreased.