Non-equilibrium molecular dynamic simulations reveal that the thermal conductivity of ultrathin carbon nanotube (CNT)(2, 1) is significantly suppressed upon hydrogenation. The addition of hydrogen atoms to two-coordinated carbon atoms lowers the participation ratios of phonon modes, thus indicating that the spatial distribution of phonons becomes localized. Furthermore, the phonon lifetimes are remarkably shortened in hydrogenated CNT(2, 1) (HCNT(2, 1)) compared with those of bare CNT(2, 1). The lowered participation ratios and lifetimes of phonon modes are responsible for the significant reduction of thermal conductivity in HCNT(2, 1). Our study is also helpful for understanding the weakened thermal transport abilities in carbon polymers, namely, the cross links formed between individual polymer chains will hinder the thermal conduction along polymers, even though the single straight carbon polymer has a high and divergent thermal conductivity. (C) 2015 AIP Publishing LLC.
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