Structural stability, electronic structure and mechanical properties of platinum group metal nitrides PGMN (PGMÂ =Â Os, Ir, Pt)

The structural stability, electronic structure and mechanical properties of platinum group metal nitrides PGMN (PGM = Os, Ir, Pt) are investigated using the first principles calculation. The structural stability is analyzed among six different crystal structures namely, NaCl, CsCl, zinc blende, NiAs, WC and wurtzite structures. The zinc blende structure is found to be the most stable one for all the three nitrides at normal pressure. A structural phase transition from zinc blende to the NiAs structure is predicted at the pressures of 71 GPa, 41 GPa and 24 GPa for OsN, IrN and PtN respectively. The electronic structure reveals that these nitrides are metallic. The high bulk modulus values of OsN, IrN and PtN indicate that these metal nitrides are super hard materials. Moreover, a positive value of calculated Cauchy pressure and a high B/G value predict that these materials are ductile in nature. The Debye temperature values are also reported for these nitrides.