Elastic and Bandgap Modulations of Hexagonal BC2N From First-Principles Calculations

The structural, elastic, and electronic properties of a potential superhard material h-BC2N as a function of external forces, including hydrostatic pressure and biaxial strains, are investigated using first-principles calculations. For both types of external forces employed, the well qualified elastic criteria and positive phonon frequencies confirm its mechanical and dynamical stability. Considerable elastic constants and elastic modulus, especially Youngs modulus (965 GPa) and shear modulus (444 GPa), are obtained at equilibrium condition. All the elastic constants and elastic modulus increase (decrease) with increasing pressure and compressive (tensile) epsilon xx along with a better (worse) ductile behavior. The theoretical Vickers hardness of h-BC2N is 70.34 GPa, which is calculated from a microscopic determined model and increases notably with pressure and compressive strain. Debye temperature and elastic anisotropy of h-BC2N are also included in this work, a sizeable Debye temperature of 2047K is obtained at ambient temperature. Besides, h-BC2N is an indirect bandgap semiconductor with E-g = 3.84 eV which can be slightly modulated by external forces.