Prediction of chirality- and size-dependent elastic properties of single-walled boron nitride nanotubes based on an accurate molecular mechanics model

• Development of an accurate molecular mechanics model for prediction of mechanical properties of chiral SWBNNTs.
• Obtaining elastic surface Young’s modulus, Poisson’s ratio and bending modulus of h-BN using the DFT.
• Evaluation of force constants appearing in the molecular mechanics model based on mechanical properties of h-BN.
• Prediction of elastic surface Young’s modulus and Poisson’s ratio of chiral SWBNNTs.

Molecular mechanics theory has been widely used to investigate the mechanical properties of nanostructures analytically. However, there is a limited number of research in which molecular mechanics model is utilized to predict the elastic properties of boron nitride nanotubes (BNNTs). In the current study, the mechanical properties of chiral single-walled BNNTs are predicted analytically based on an accurate molecular mechanics model. For this purpose, based upon the density functional theory (DFT) within the framework of the generalized gradient approximation (GGA), the exchange correlation of Perdew–Burke–Ernzerhof is adopted to evaluate force constants used in the molecular mechanics model. Afterwards, based on the principle of molecular mechanics, explicit expressions are given to calculate surface Young’s modulus and Poisson’s ratio of the single-walled BNNTs for different values of tube diameter and types of chirality. Moreover, the values of surface Young’s modulus, Poisson’s ratio and bending stiffness of boron nitride sheets are obtained via the DFT as byproducts. The results predicted by the present model are in reasonable agreement with those reported by other models in the literature.