Investigation of structural stability and electronic properties of group III nitrides: a first principles study

The high-pressure structural phase transition, electronic, superconducting and elastic properties of group III nitrides (ScN, YN and LaN) are investigated by first principles calculation with the density functional theory. The calculated lattice parameters are in good agreement with the experimental and other theoretical values. Electronic structure reveals that these materials are semiconductors with an indirect band gap of 1.4, 0.87 and 0.65?eV for ScN, YN and LaN, respectively. The obtained cubic NaCl structure is energetically the most stable structure at ambient pressure. A pressure-induced structural phase transition from NaCl to CsCl structure is predicted. The structural phase transition of ScN, YN and LaN occurs at a pressure of 158, 132 and 26.5?GPa, respectively. On further increase in the pressure, semiconductor-to-metallic transition and superconductivity is observed in these nitrides. The estimated T _c values as a function of pressure for ScN, YN and LaN are 31.79, 15.50 and 12.84?K, respectively.