Density function theory study of electronic, optical and thermodynamic properties of CaN 2 , SrN 2 and BaN 2

We put forward a first-principles density-functional theory about the impact of pressure on the structural and elastic properties of bulk CaN 2 , SrN 2 and BaN 2 . The ground state properties of three alkaline earth diazenides were obtained, and these were in good agreement with previous experimental and theoretical data. By using the quasi-harmonic Debye model, the thermodynamic properties including the debye temperature Θ D , thermal expansion coefficient α , and grüneisen parameter γ are successfully obtained in the temperature range from 0 to 100 K and pressure range from 0 to 100 GPa, respectively. The optical properties including dielectric function ε ( ϖ ), absorption coefficient α ( ϖ ), reflectivity coefficient R ( ϖ ), and refractive index n ( ϖ ) are also calculated and analyzed.