Transformation of electronic properties and structural phase transition from HfN to Hf3N4...

We report investigation of the structural phase transition and electronic properties of Hf1-xN (0 <= x <= 0.25) using first principles calculations. The defective NaCl-type structure with Hf vacancies (V-Hf) is found to be stable over a large phase region. Hf3N4 with the Zr3N4-type structure is only stable in relative small region and readily destabilized when the stoichiometric ratio of N to Hf deviates from 4/3. The electronic and optic properties of Hf1-xN are controlled by the concentration of V-Hf. The full depletion of excess free electrons from Hf atoms results in the structural phase transition of Hf3N4.