  In this paper, we propose a combined modeling of molecular mechanics (MM) and
the tight-binding (TB) approach, which enables us to study the effect of
factors such as external local forces, constraints, and vacancy defects on
electronic transport properties of nanomaterials. Nanostructures selected in
this work are armchair graphene nanoribbons (AGNRs). According to this method,
the nanostructure is modeled as a frame, and the beam element is applied for
illustrating the covalent interatomic interactions in bonds. In our
calculations, the terms of torsional, stretching, and bending energies are
considered. The selected pristine nanoribbon is a metal, and the purpose of
this study is to find the effects of mechanical loading, the vacancy defects
and their positions on the electrical conductance of the structure. We observe
that the presence of vacancy defects in the structure leads to the opening of
an energy gap, which changes the phase of the nanostructure from metal to the
semiconductor. We find that with increasing the number of point defects, the
energy gap size of the strained system grows. Besides, increasing the magnitude
of the local force reduces the conductance, and the energy gap of the system.
By changing parameters such as the number of point defects and magnitude local
forces, the transport gap of the system can be controlled. The results of this
research may be useful in the design of nanoelectromechanical systems.
