First-principles investigations on structural stability, elastic and electronic properties of Co7M6 (M= W, Mo, Nb) µ phases

Abstract

ABSTRACTThe structural, elastic and electronic properties of Co7M6 (M = W, Mo, Nb) μ phases were investigated by first-principles calculations based on the density functional theory (DFT). The calculated cohesive energy indicates that Co7M6 (M = W, Mo, Nb) μ phases are thermodynamically stable. Besides, Co7W6 owns a higher structural stability than that of Co7Mo6 and Co7Nb6. The obtained elastic constant demonstrates that Co7M6 (M = W, Mo, Nb) are mechanically stable. With Voigt-Reuss-Hill (VRH) approximation, the elastic bulk modulus (B), shear modulus (G), Young's modulus (E) and Poisson's ratio (ν) were derived. The ductility and plasticity as well as the elastic anisotropy of the three phases were discussed in details. Finally, the density of states and charge density difference were also analysed to reveal the underlying mechanism of structural stability and the elastic properties.