Mechanical Properties and Electronic Structures of M (M=Ti, V, Cr, Mn and Fe) Doped β-Si3N4 from First-Principle

The structures, mechanical properties and electronic structures of M metals (M=Ti, V, Cr, Mn and Fe) doped beta-Si3N4 were investigated by First-principles calculations within CASTEP. The calculated lattice parameters of beta-Si3N4 were consistent with previous date. The cohesive energy and formation enthalpy show that initial beta-Si3N4 has the highest structural stability. The calculated elastic constant and the Voigt-Reuss-Hill approximation indicate that elastic moduli of beta-Si3N4 are slightly reduced by M doping. Based on Poisson's and Pugh's ratio, beta-Si(3)N(4 )is a ductile material and the toughness of beta-Si(3)N(4 )increases with M doping, and Fe doping exhibited the best toughness. The results of density of states, charge distributions and overlapping populations indicate that beta-Si3N4 has the strong covalent and ionic bond strength between N and Si.