  Carbon nanotubes can serve as one-dimensional nanoreactors for the in-tube
synthesis of various nanostructures. Experimental observations have shown that
chains, inner tubes, or nanoribbons can grow by the thermal decomposition of
organic/organometallic molecules encapsulated in carbon nanotubes. The result
of the process depends on the temperature, the diameter of the nanotube, and
the type and amount of material introduced inside the tube. Nanoribbons are
particularly promising materials for nanoelectronics. Motivated by recent
experimental results observing the formation of carbon nanoribbons inside
carbon nanotubes, molecular dynamics calculations were performed with the open
source LAMMPS code to investigate the reactions between carbon atoms confined
within a single-walled carbon nanotube. Our results show that the interatomic
potentials behave differently in quasi-one-dimensional simulations of
nanotube-confined space than in three-dimensional simulations. In particular,
the Tersoff potential performs better than the widely used Reactive Force Field
potential in describing the formation of carbon nanoribbons inside nanotubes.
We also found a temperature window where the nanoribbons were formed with the
fewest defects, i.e., with the largest flatness and the most hexagons, which is
in agreement with the experimental temperature range.
