DFT Study of Aln (1-13) Clusters Encapsulated Inside Single Walled Carbon Nanotubes

We have carried out a systematic investigation of encapsulation of Al-n clusters for n = 1-13 inside armchair single walled carbon nanotubes (SWCNTs)(m,m) of varying diameter using density functional theory calculations. The effect of confinement was studied on the Al-n geometries which shows linear structures for n <= 5 in SWCNTS (m,m) [m < 7] and 3D) structures thereafter for n > 5 and m > 6. In strong confinement. Al-C interaction becomes more dominant and if we relax the effect of confinement, then the Al-Al interactions become relatively more important. It was observed that the clusters have a tendency to form nanowires in strong confinement and retain their free space geometries in less confinement. The HOMO-LUMO gap of the hybrid structures Al-n@(6, 6) for n = 1-13 decreases to 0.10-0.20 eV w.r.t pure SWCNTs. In Al-n@(8,8), the HOMO-LUMO gap shows an oscillatory odd even pattern, with higher values for odd n (n > 5) and a maximum value of 1.11 eV for n = 7. The Mulliken charge analysis on Al-n@SWCNT, shows a significant variation on A I atomic sites which are near to SWCNT wall due to the charge transfer from C atom to Al atoms.