Electronic structure, structural stability, mechanical and superconducting properties of group VB nitrides: A first principles study

The electronic, structural, mechanical and superconducting properties of group VB mononitrides are investigated by means of first principles calculation based on density functional theory with generalized gradient approximation. The calculated ground state properties are in good agreement with previous experimental and theoretical results. Among the three crystallographic structures that have been investigated, the hexagonal WC phase is found to more stable than the cubic ones. Under high pressure, a series of structural phase transition from WC → NaCl → CsCl phase is also predicted in VN, NbN and TaN. The calculated elastic constants indicate that all the three nitrides are mechanically stable at ambient pressure. The estimated Zener ratio and linear compressibility coefficients Kc/Ka reveals that these materials exhibit elastic anisotropy. The estimated superconducting transition temperature (Tc) values as a function of pressure for VN, NbN and TaN are 35.5, 37.5 and 30.5 K respectively.

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► The DFT calculations have been performed for group VB nitrides.
► Calculated elastic moduli obey traditional mechanical stability condition.
►  Tantalum nitride is the hardest material among the group VB nitrides.
► Calculated Tc values as a function of pressure are (35 K) VN, (37 K) NbN and (30 K) TaN.