Ab initio study of curvature effects on the physical properties of the Xe-doped nanotubesand nanoropes

Abstract

A systematic comprehensive ab initio investigation of the energetics, structural, electronic,and optical properties of weakly and heavily Xe-doped ultrathin 4 Å and large-diametercarbon nanotubes has been performed. The contributions of the dispersion as well as thezero-point energies have been considered. The effects of the tube diameter and the differentchiralities of the carbon nanotubes on the adsorbant-induced physical propertieshave been investigated. The favoured tubes for Xe atom adsorption are armchair(n,n) tubes, and one may not observe any appreciable surface Xe adsorption on zigzag(n,0) orchiral (m,n) tubes. The band gap of a semiconducting achiral zigzag nanotube is reduced whereasthe band gap of a chiral semiconducting tube is enhanced by the adsorption ofXe atoms. Xe adsorption in/on the metallic tubes creates extra (one or more)conductive channels which run inside/outside the nanotubes and may result in quiteenhanced conduction. The optical absorption of the achiral (chiral) 4 Å diametertube is considerably changed (unchanged) by the adsorption of the Xe atoms.The calculated peaks in large-diameter pristine nanotubes have been detectedin the experimental measurements. In the (10, 0) and (10, 10) nanotubes, thesmall adsorption of Xe does not change the optical absorption of the pristinetube. The computed binding energy and the saturation Xe concentration arein reasonable agreement with the experimental data available for the (10, 10)nanotube.