One-Dimensional Oxygen and Helical Oxygen Nanotubes inside Carbon Nanotubes

The low-temperature structures of a model oxygen system confined within single-walled carbon nanotubes (SWCNTs) of several diameters ranging from 0.6 to 2.0 nm were investigated by molecular dynamics calculations. It was found that as the SWCNT diameter increases, the following five oxygen structures form successively: a linear geometry one-dimensional (1D) chain, a cross (X) geometry 1D chain, a parallel geometry zigzag chain, a helical geometry nanotube, and a multilayer nanotube. In most cases, magnetic exchange interactions between nearest-neighbor oxygen molecules are expected to be antiferromagnetic, although some may be ferromagnetic. It is expected that the oxygen inside SWCNTs exhibits the various features of a quasi-1D spin 1 magnet.