Mapping temperature and confinement dependence of carbyne formation within carbon nanotubes

Abstract

Single atomistic chains of carbon – a.k.a. carbyne – are of great interest due to their attractive properties. One route of proposed synthesis is exploiting the interior of a carbon nanotube, enabling sufficient alignment and affable temperature conditions for chain growth. Here, we delineate the optimal conditions for growth by means of full atomistic modeling of sequential carbon reactions inside single walled carbon nanotubes (SWCNTs). Seeding the interior of a SWCNT with free carbons, we vary the nanotube diameters and temperature, and compare the resulting chain lengths. We systematically study the affecting factors of carbyne synthesis, investigating the effects of temperature, confinement (via nanotube diameter) and alignment (using polymer shape metrics). We verify with prior experimental studies that carbyne can be successfully synthesized when the inner diameter is less than approximately 9 Å and temperature is higher than 500 K. Additionally, we map the chain length with respect to the nanotube diameter and the temperature and propose a simple empirical/phenomenological relation to predict growth rate based on classical collision theory with a modified Arrhenius relation.