Exploring the simultaneous existence of Stone-Wales and carbon ad-dimer defects in the zigzag single-walled carbon nanotubes

•Formation of CD defect is easier than SW rearrangement.•Formation of CD defect on SW defective SWCNT is more favorable than perfect ones.•Formation of SW defect on CD defective SWCNT is more favorable than perfect ones.•Defect formation shows dependence on the radius and defect orientation.•Histograms of 13C chemical shifts exhibit individual signals for defect sites.

We have applied density functional calculations to investigate simultaneous existence of Stone–Wales (SW) and carbon ad-dimer (CD) defects in the zigzag (n, 0) n=5, 6, 7, 8, 9, and 10 SWCNTs, with an extensive search by considering two different orientations of defects. According to our results, the adsorption of a carbon dimer on a hexagonal ring of SWCNTs is easier than the rotation of a C–C bond trough the SW rearrangement. Moreover, the formation of a carbon dimer on the exterior sidewalls of an SW defective SWCNT or the rotation of a C–C bond of a CD defective SWCNT is more favorable than those on the perfect ones. Defect formation energy shows a strong dependence on the both SWCNT radius and defect orientation. The reactivity of SW–CD defective SWCNTs through chemisorption of hydrogen atoms on the central bonds of defect sites shows the thermodynamically lower preference of additions for the CD defective sites in comparison to SW defective sites. Histograms of the 13C NMR chemical shifts of SW–CD defective SWCNTs exhibit individual signals for defect sites, which can be attributed to azupyrene- and pentalelene-like structures for SW and CD defect sites, respectively.

Graphical abstractCoexistence of Stone Wales and Carbon ad-dimer defects.Figure optionsDownload full-size imageDownload as PowerPoint slide