Polyyne chain growth and ring collapse drives ni-catalyzed swnt growth: A QM/MD investigation

A mechanism describing Ni₃₈-catalyzed single-walled carbon nanotube (SWNT) growth has been elucidated using quantum mechanical molecular dynamics (QM/MD) methods. This mechanism is dominated by the existence of extended polyyne structures bound to the base of the initial SWNT cap-fragment. Polygonal ring formation, and hence SWNT growth itself, was driven by the continual, simultaneous extension of these polyyne chains and subsequent "ring collapse" (i.e., self-isomerization/interaction of these polyyne chains). The rate of the former exceeded that of the latter, and so this mechanism was self-perpetuating. Consequently, the observed kinetics of Ni ₃₈-catalyzed SWNT growth were increased substantially compared to those observed using other transition metal catalysts of comparable size.