EARLY STAGE IN THE NUCLEATION PROCESS OF CARBON NANOTUBES: DENSITY-FUNCTIONAL TIGHT-BINDING MOLECULAR DYNAMICS SIMULATIONS OF ACCETYLENE OLIGOMERIZATION AND CROSS-LINKING ON AN FE_(38) PARTICAL

摘要

Catalytic chemical vapor deposition (CCVD) is typically used to synthesize carbon nanotubes (CNTs), but the exact role of metal catalysts is still unknown. Since Fe substrate is known to be highly effective for the CNT growth in the CCVD process and C2H2 is an excellent carbon source for high yield, we performed quantum chemical molecular dynamics (QM/MD) simulations based on the density-functional tight-binding (DFTB) method to investigate the self-assembly process of carbon nanotubes from acetylene molecules on an Fe_(38) particle. We found that oligomerization and cross-linking reactions between carbon chains with high H:C ratio were observed as initial steps, preceding any future cap nucleation.