Theoretical study of elastic and thermodynamic properties of η-Ta2N3

We present a detailed theoretical study of the elastic properties of η-Ta2N3 under pressure ranging from 0 GPa to 80 GPa by plane-wave pseudopotential density functional theory with the generalized gradient approximation in this paper. The results show that η-Ta2N3 is mechanically unstable at ambient conditions because of a negative C66, and it will be stable when the pressure is up to 10.7 GPa. The thermodynamic properties of η-Ta2N3 are also investigated through quasi-harmonic Debye model in a pressure range of 0-80 GPa and a temperature range of 0-1500 K. The Debye temperature, heat capacity and thermal expansion with pressure and temperature are successfully obtained and discussed.