Temperature Effect on Young's Modulus of Boron Nitride Sheets

In this article, based on the oscillations of atoms due to the thermal effects (i.e., thermal phonons), Young's modulus of a hexagonal boron nitride sheet at different environment temperatures is investigated. To this end, the density functional theory (DFT) and quasi-harmonic approximation (QHA) are applied to calculate the energies of electrons and phonons, respectively, and then to obtain the total energy of the system. Unlike graphene, Young's modulus of boron nitride sheets tends to considerably increase with the increase of temperature to a specific value about 800 K. For the temperatures greater than 800 K, variation of Young's modulus with temperature is not considerable so that it can be neglected at high temperatures. It is also discerned that when temperature is high, the effect of phonon energy on Young's modulus is negligible.