The (<i>n,m</i>) nanotube naming scheme can be thought of as a vector (C<sub>h</sub>) in an infinite graphene sheet that describes how to 'roll up' to graphene sheet to make the nanotube. T denotes the tube axis, and <i>a<sub>1</sub></i> and <i>a<sub>2</sub></i> are the unit vectors of graphene in real space. It is based upon similar diagrams found in the literature (for instance, Odom et al. Topics Appl. Phys., 2001, 80, 173).
<a href="//commons.wikimedia.org/wiki/User:Andel" title="User:Andel">Andel</a>
own work, following a picture by <a href="https://en.wikipedia.org/wiki/User:Kebes" class="extiw" title="en:User:Kebes">Kebes</a>