  This study of elastic and plastic deformation of graphene, silicene, and
boron nitride (BN) honeycomb nanoribbons under uniaxial tension determines
their elastic constants and reveals interesting features. In the course of
stretching in the elastic range, the electronic and magnetic properties can be
strongly modified. In particular, it is shown that the band gap of a specific
armchair nanoribbon is closed under strain and highest valance and lowest
conduction bands are linearized. This way, the massless Dirac fermion behavior
can be attained even in a semiconducting nanoribbon. Under plastic deformation,
the honeycomb structure changes irreversibly and offers a number of new
structures and functionalities. Cagelike structures, even suspended atomic
chains can be derived between two honeycomb flakes. Present work elaborates on
the recent experiments [C. Jin, H. Lan, L. Peng, K. Suenaga, and S. Iijima,
Phys. Rev. Lett. 102, 205501 (2009)] deriving carbon chains from graphene.
Furthermore, the similar formations of atomic chains from BN and Si nanoribbons
are predicted.
