The vapour-liquid-solid (VLS) model, which often includes a temperature gradient (TG) across the catalytic metal particle, is often used to describe the nucleation and growth of carbon nanostructures. Although the TG may be important for the growth of carbon species from large metal particles, molecular dynamics simulations show that it is not required for single-walled carbon nanotube growth from small catalytic particles. (C) 2004 Elsevier B.V. All rights reserved.