Insertion of C50 into single‐walled carbon nanotubes: Selectivity in interwall spacing and C50 isomers

The structures and electronic properties of nanoscale “peapods,” i.e., C50 fullerenes inside single‐walled carbon nanotubes (SWCNTs), were computationally investigated by density functional theory (DFT). Both zigzag and armchair SWCNTs with diameters larger than 1.17 nm can encapsulate C50 fullerenes exothermically. Among the SWCNTs considered, (9,9) and (16,0) SWCNTs are the best sheaths for both D3 and D5h isomers of C50, corresponding to 0.32–0.34 nm tube‐C50 distances. The orientation of C50 inside nanotubes also affects the insertion energies, which depend on the actual tube‐fullerene distances. The insertion of D3 and D5h isomers of C50 is somewhat selective; the less stable D5h isomer can be encapsulated more favorably inside SWCNTs at same tube‐C50 spacing. Because of the weak tube‐C50 interaction, the geometric and electronic structures of the peapods do not change greatly for the most stable configurations, but the selectivity in the interwall spacing and isomer encapsulation can be useful in separating various carbon fullerenes and their isomers. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008