A first-principles study of novel cubic AlN phases

Abstract

By a first-principles approach combined with an evolutionary method, four novel cubic AlN phases (cP16, cF40, cI16, and cI24 AlN) are proposed as promising phases after detailed stability analysis. These four cubic AlN phases exhibit a hardness range of 7.8–17.0 GPa. The anisotropy of their mechanical properties, including Young's modulus, shear modulus, and Poisson's ratio, is systematically studied. Moreover, they are all semiconductors with band gaps smaller than those of experimental phases, and consist of polar covalent Al–N bonds with sp3 hybridization. Their thermodynamic functions, including enthalpy, Gibbs free energy, and vibrational entropy, are calculated in the temperature range from 0 to 2000 K. Their thermodynamic properties, including Debye temperature and constant-volume specific heat, are investigated. The anisotropy of their minimum thermal conductivities is discussed on the basis of Clarke's model. We hope that this study of the mechanical, electronic, and thermodynamic properties of novel cubic AlN phases will provide guidance for the industrial applications of these four cubic AlN phases.