The influence of magnetic moment on carbon nanotube nucleation

We demonstrate the impact of magnetic moment on single-walled carbon nanotube (SWCNT) nucleation, using quantum chemical molecular dynamics simulations. The mechanism of SWCNT cap formation on Fe₃₈ nanoparticle catalysts can be manipulated by altering the total magnetic moment. When the magnetic moment is low, large cap structures dominated by pentagons are formed. Increasing the magnetic moment leads to smaller, "flatter" sp² carbon networks with a higher proportion of hexagons, which are incapable of lifting away from the catalyst surface. These results demonstrate that SWCNT (n,m) chirality distributions can be potentially manipulated via altering the magnetic moment of the catalyst-carbon interface. We also show that higher magnetic moments leads to slower SWCNT nucleation. This is a consequence of the extent of Fe → C charge transfer, which is proportional to the total magnetic moment. As the magnetic moment is increased, the Fe₃₈ nanoparticle has higher catalytic activity and is able to stabilise carbon in its subsurface region, thereby impeding the nucleation process.