Structure reconstruction of TiO2-based multi-wall nanotubes: first-principles calculations

Abstract

A new method of theoretical modelling of polyhedral single-walled nanotubes based on the consolidation of walls in the rolled-up multi-walled nanotubes is proposed. Molecular mechanics and ab initio quantum mechanics methods are applied to investigate the merging of walls in nanotubes constructed from the different phases of titania. The combination of two methods allows us to simulate the structures which are difficult to find only by ab initio calculations. For nanotube folding we have used (1) the 3-plane fluorite TiO2 layer; (2) the anatase (101) 6-plane layer; (3) the rutile (110) 6-plane layer; and (4) the 6-plane layer with lepidocrocite morphology. The symmetry of the resulting single-walled nanotubes is significantly lower than the symmetry of initial coaxial cylindrical double- or triple-walled nanotubes. These merged nanotubes acquire higher stability in comparison with the initial multi-walled nanotubes. The wall thickness of the merged nanotubes exceeds 1 nm and approaches the corresponding parameter of the experimental patterns. The present investigation demonstrates that the merged nanotubes can integrate the two different crystalline phases in one and the same wall structure.

Theoretical study of α- and γ-V2O5 double-walled nanotubes

“…The results obtained for the bulk V 2 O 5 using the Grimme correction agree well with the experimental data [20]. The scaling factor s 6 is set to 0.5 according to [21], whereas the steepness d and the cutoff radius R cut for direct lattice summation are set equal to 20 and 25.0 Å, respectively. Brillouin zone (BZ) integration was performed over 12 k-points chosen according to the Monkhorst-Pack scheme [22].…”

“…While the length of an outer wall is constant, the formation of puckering regions with separated walls is observed as well. It should be noted that during geometry optimization no consolidation of two walls into one thick wall is observed, in contrast to TiO 2 DWNTs [21].…”

Electronic Structure Controlling of Assembly and Optical Properties of TiO2 Nanotube Arrays

“…Therefore, the additions of these ions cause a decreasing of stability of (9, 0) nanotube. It is worth to note that the configurations of the nanotubes with consolidated single wall are really complex, and the consolidated model does not always improve the stability of nanotubes . Therefore, the consolidated model of nanotubes is not further considered.…”

Ab initio modeling of single wall nanotubes folded from α- and γ-V2O5 monolayers: structural, electronic and vibrational properties

“…The scaling factor s 6 corresponding to the calculation of Grimme correction using PBE0 is set to 0.5 according to ref. 31, whereas the steepness d and the cutoff radius R cut for direct lattice summation are equal to 20 and 25.0 Å, respectively.…”