Mixed finite element-tight binding electromechanical analysis of carbon nanotubes

Electrical transport properties of carbon nanotubes can be dramatically changed by mechanical deformations that alter tube shape and the corresponding positions of the atoms comprising the tube wall. In principle, detailed atomic/electronic calculations can provide both the deformed configuration and the resulting electrical transport behavior of the tube. Here we simplify the process by refining a previously-developed nonlinear structural mechanics finite-element-based procedure for modeling mechanical behavior of carbon nanotubes to account explicitly for tube chirality. A quadrilateral element overlay procedure provides an isotropic finite element model of hexagonal cells within a graphene sheet, with the only nodal positions coincident with those of the atoms. Mechanical deformation of the nanotube structure is simulated with finite elements, and the evolving atomic [nodal] coordinates are processed within the finite element (FE) program by using a tight-binding (TB) code to calculate deformation-induced changes in electrical transport properties of the nanotube. Results of the mixed FE/TB calculations compare favorably with existing atomistic simulations of single-walled nanotubes subjected to torsion, intense lateral squeezing, and large, kink-producing bending.