On the role of interatomic potentials for carbon nanostructures.

This work provides a contribution to the critical dissection of interatomic potentials for carbon nanostructures (sp2 carbon nanoforms), within the framework of atomistic models. Within the vast family of empirical potentials, the discussion focuses on those characterized by only short-range interactions which, due to their simplicity, are suitable for a FEM implementation in Molecular Mechanics, and can be easily incorporated in continuum models, through appropriate constitutive identification procedures. After a first selection of the potentials on the basis of the stated criteria, their parameters are calibrated starting from the ab-initio results found in the literature. The performances of the potentials are compared in both armchair and zigzag tensile tests under periodic conditions and up to failure, and some considerations about their trend in terms of inner forces and couples are made. From this comparison the proposal of a new interatomic potential arises, which we call damped DREIDING and use to perform tensile tests on graphene sheets of finite size. The problem of the alleged auxeticity of graphene in the armchair direction is also discussed