Effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of t-C_8B_2N_2

摘要

135103.1-135103.9%The effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of a superhard material t-C8B2N2 have been studied using first-principles calculations. The structure is proven to be mechanically and dynamically stable under the applied external forces. All the elastic constants (except C-66) and elastic modulus increase (decrease) with increasing pressure and compressive (tensile) biaxial strain epsilon(xx). A microscopic model is used to calculate the Vicker's hardness of every single bond as well as the crystal. The hardness of t-C8B2N2 (64.7 GPa) exceeds that of c-BN (62 GPa) and increases obviously by employing pressure and compressive epsilon(xx). Furthermore, the Debye temperature and anisotropy of sound velocities for t-C8B2N2 have been discussed. t-C8B2N2 undergoes an indirect to direct bandgap transition when epsilon(xx) 2%; however, the indirect bandgap character of the material remains under pressure. Published by AIP Publishing.