Influence of F centres on structural and electronic properties of AlN single-walled nanotubes

Abstract

We analyse the influence of uncharged N vacancies (neutral F centres), created either under conditions of AlN nanotube growth or by its soft irradiation, on the atomic and electronic structure. Periodic one-dimensional (1D) density functional theory (DFT) calculations on models of defective single-walled nanotubes (SW NTs) allow us to analyse how NT chirality and concentration of F centres change their properties compared to the corresponding defect-free nanotubes. We have simulated reconstruction around periodically repeated F centres on 1 nm AlN SW NTs with armchair-and zigzag-type chiralities. To achieve the limit of an isolated vacancy for both chiralities, we have considered different inter-defect distances repeated along the axes of these nanotubes. For d F-F 20Å, the interaction between defects is found to be negligible, since energy dispersion does not exceed 0.02 eV. We also analyse the influence of F centres on the energy cost required to wrap up AlN graphitic nanosheets (NSs) of both chiralities into the corresponding 1 nm thick SW NTs. The electronic properties of defective NS and NTs of both chiralities have been compared with those for defective AlN bulk three-dimensional (3D) structures of wurtzite and zinc-blend. The presence of N vacancies in various aluminium nitride structures (including SW NTs) results in the appearance of defect energy levels in the band gap with the prevailing contribution from 3s and 3p atomic orbitals of the nearest Al atoms. We have found that the larger the concentration of F centres is, the smaller the maximal energy gap between defect levels is, i.e. an increase 7

Ab initio simulations on the atomic and electronic structure of single-walled BN nanotubes and nanoarches

“…Similar theoretical simulations were successfully performed by us recently, in order to study periodic 1D, 2D and 3D AlN structures, both regular 37 and defective. 38 . In the current…”

Simulations on the mechanism of CNT bundle growth upon smooth and nanostructured Ni as well as θ-Al2O3 catalysts

“…Earlier, this LCAO formalism was successfully applied by us for simulations on: ( ) smooth and nanostructured Ni(111) substrates [24], (ii) α-Al 2 O 3 (0001) surface [25], (iii) SW nanotubes of AlN [26] and BN [27]. In the current study, we have used the all-valence basis sets (BSs) of atomic GTFs (constructed using pure -andas well as hybrid sp-AOs) 1 as described elsewhere: Ni [24], Al (8 -621sp-1 ) [26] and O (8 -411sp-1 ) [27] which have been slightly re-optimized for valence and virtual shells. The BS of C atom in the suggested form (6 -311sp-11 ) 1 have also been re-optimized.…”

2D Slab Models of Nanotubes Based on Tetragonal TiO2 Structures: Validation over a Diameter Range

“…The photocatalytic potential of nanotubes, nanorods, and nanowires is frequently studied. The favorable effect of low dimensions is especially prominent in NTs due to their hollow structure [ 41 , 42 ].…”