  This paper proposes a bottom-up sequence of modeling steps leading to a
nanoscopically informed continuum, and as such macroscopic, theory of
single-walled carbon nanotubes (SWCNTs). We provide a description of the
geometry of the two most representative types of SWCNTs, armchair (A-) and
zigzag (Z-), of their modules and of their elementary bond units. We believe
ours to be the simplest shell theory that accounts accurately for the linearly
elastic response of both A- and Z- CNTs. In fact, our theory can be shown to
fit SWCNTs of whatever chirality; its main novel feature is perhaps the
proposition of chirality-dependent concepts of effective thickness and
effective radius.
