  A two-field model provides an unifying framework for elasticity, lattice
dynamics and electromechanical coupling in graphene and carbon nanotubes,
describes optical phonons, nontrivial acoustic branches, strain-induced gap
opening, gap-induced phonon softening, doping-induced deformations, and even
the hexagonal graphenic Brillouin zone, and thus explains and extends a
previously disparate accumulation of analytical and computational results.
