Quantum effects on the elastic properties of cubic boron nitride by path-integral Monte Carlo simulation

Abstract

Using path-integral Monte Carlo simulation, we study the quantum effects on the elastic properties of cubic boron nitride (c-BN) crystal in a wide temperature range from 40 to 2000 K and a pressure range varying from 1 atm to 160 GPa. The Tersoff–Albe potential is employed to describe the interatomic interactions, and the elastic constants are determined by a direct method derived from the stress–strain curves. The calculations show that elastic constants C11, C12, and C44 are temperature and pressure dependent, and their values are in satisfactory agreement with available experimental results at room temperature. Furthermore, we estimate the Poisson ratio, anisotropic factor, longitudinal-wave elastic constant, Cauchy pressure, and Pugh’s ratio and their temperature and pressure dependence. In general, the quantum effect contributions to the elastic properties of the c-BN are extracted quantitatively from the differences between the path-integral and classical Monte Carlo simulation results. The quantum contribution is negligible at high temperatures but can be significant at low temperatures. It is responsible for variations of about 5∼7% of the elastic constants C11 and C44, and C12. The impacts of quantum contribution on the elastic properties of the c-BN crystal are similar to those found in the diamond.