Structure of narrow-diameter single-wall carbon nanotubes grown in $\mathrm{Al}\mathrm{P}{\mathrm{O}}_4\text{−}5$ zeolite

We present a grand canonical Monte Carlo simulation study of carbon adsorption in $\mathrm{Al}\mathrm{P}{\mathrm{O}}_4\text{−}5$ (AFI) zeolite. An order $N$ simplified tight binding model is used for carbon-carbon interactions, and the carbon-matrix interaction is assumed to be weak in the physisorption range. Comparing the almost perfect tubes formed in smooth cylindrical channels and those numerically grown in AFI, we can assess the role of the carbon-wall interaction. In AFI, we obtain defective single-wall nanotubes with a diameter of $\approx 4\mathrm{\AA }$, in good agreement with experiments. The tube is thermally stable and presents a mixture of different chiral patterns. The energy cost associated with the defects is about $0.15\mathrm{eV}$/atom, indicating that the probability of obtaining defective tubes, with portions of different chiralities along the same zeolite channel, is large.

Figure 1

(Color online) Tubes grown in AFI (left, sample 1), in $4.2\mathrm{\AA }$ (center, sample 2), and in $4\mathrm{\AA }$ (right, sample 3) smooth cylindrical channels.

Figure 2

(Color online) Radius distribution of samples 1 (black), 2 (red), and 3 (green).

Figure 3

(Color online) A relaxed in-$\mathrm{Al}\mathrm{P}{\mathrm{O}}_4\text{−}5$-grown tube.