Binding ofNH3to graphite and to a (9,0) carbon nanotube

The interaction of $\mathrm{N}{\mathrm{H}}_3$ with graphite and a (9,0) carbon nanotube is studied using the second-order Møller-Plesset and density functional theory approaches. For both graphite and the nanotube, our best estimate of the $\mathrm{N}{\mathrm{H}}_3$ binding energy is $2\pm 2\mathrm{kcal}∕\mathrm{mol}$. $\mathrm{N}{\mathrm{H}}_3$ physisorbs on the carbon surface and the hydrogen end points toward the carbon surface. The binding is mostly electrostatic in nature and there is very little charge transfer occurring. Band-structure calculations on a (10,0) semiconducting nanotube show essentially no change in the nanotube band gap when $\mathrm{N}{\mathrm{H}}_3$ is added. The implications of these calculations on the experimental results are discussed.