C13 – a new empirical force field to characterize the mechanical behavior of carbyne chains

An accurate prediction of the mechanical behavior of long carbyne chains depends on the suitable modeling of bond alternation in these chains. While first-principles methods are a good approach, less computationally demanding empirical potentials are preferable for large carbyne-containing systems. AIREBO and Reax empirical potentials have extensively and successfully been used for simulating the mechanical behavior of graphene and carbon nanotubes. However, it remains unclear if these potentials can be directly applied in the accurate mechanical modeling of carbon nanostructures with sp hybridization, without re-parameterization. Here, a new force-field for carbyne, designated as C13 potential, that takes bond alternation into account, is presented. This new empirical potential was parameterized from ab initio calculations. Molecular dynamics (MD) simulations using the developed force-field are then conducted to determine the mechanical properties of carbyne chains under tensile loading, namely to assess their dependence on chain length and temperature. The bending stiffness of carbyne and its persistence length are also calculated. The results obtained are validated through comparison with results available in the literature. Lastly, the C13 potential is employed to model, for the first time, the tensile and the compressive behaviors of the hybrid system composed of carbon nanotubes infilled with carbyne chains.