A Molecular Dynamics Based Comparison of the Mechanical Properties of Three Polytypes of Cubic BC3

Abstract

In this work molecular dynamics simulations are employed to compare the mechanical properties and hardness of three polytypes of cubic BC₃. Firstly, two interatomic Tersoff potentials, with different parameterizations, were identified from the literature for the boron-carbon system. Based on cohesive energies and structural properties from existing ab-initio studies, the suitability of the two potentials for predicting the properties of BC₃ was analyzed. Secondly, using the better interatomic potential, more detailed molecular dynamics simulations were conducted to estimate and compare the elastic, yield, post-yield behavior and hardness of the three polytypes. The elastic constants compare well with existing abinitio values and vary by at most by 15% amongst the three polytypes. Response to indentation showed considerable qualitative differences in yield and post-yield response. One of the polytypes showed lower yield strength and seemed more ductile than the other two. The hardness also showed a complex dependence on both the material and the indentation depths. A peculiar, indenter-size dependent pile-up behavior was also seen. Specifically, for lower radii, pile-up was seen on indentation. As the radius of the indenter was increased, pile-up was seen only on retracting the indenter. The higher volume occupied by the indentation-amorphized material was found to be the reason for pile-up on retracting the indenter.