The purpose of this simulation is to illustrate how different temperatures and pressures affect the morphology of carbon nanotubes grown by chemical vapor deposition (CVD) of acetylene. It is based upon observations from recent CVD synthesis experiments done at the LeRoy Eyring Center for Solid State Science at ASU and discussed in "Dynamic observations of the effect of pressure and temperature conditions on the selective synthesis of carbon nanotubes" Renu Sharma et. al., Nanotechnology 18 No 12 (28 March 2007).
Straight-growing carbon nanotubes are composed of a 6-ring periodic structure. The presence of defects in the form of 5-ring / 7-ring pairs result in bends and diameter changes in the nanotube. Defects can be removed from the growth tip via an annealing process but are permanently embedded further down the tube. The annealing process is more effective at higher temperatures and lower pressures which will generate straight nanotubes. Bending tubes occur by either lowering the temperature or raising the partial pressure of acetylene gas.