Abstract: The energy bands,electronic structures of CuN₃ and AgN₃ crystallines were investigated by periodic ab initio method.The charge density projection shows that there are overlaps of isodensities between the terminal nitrogen and metallic ion,indicating that the metals and the azides are combined by covalent bonds.The crystal lattice energies are-781.05 and-840.83 kJ/mol for CuN₃ and AgN₃ respectively.These results approach the data obtained by Gray's approximate method.The frontier crystal orbital mainly consists of the atomic orbital of azide's terminal nitrogen.The energy gap for AgN₃ is smaller than that of CuN₃,and the highest occupied crystal orbitals of AgN₃ consist of both the atomic orbitals of the terminal nitrogen in azide and the silver ion,which facilitates the electron to leap from terminal nitrogen in azide to metallic ion directly.Hence silver azide is slightly more sensitive than copper azide.The elastic coefficients C₁₁,C₂₂ and C₃₃ of CuN₃ are predicted to be 96.52,96.86 and 154.06 GPa,C₁₁ and C₂₂ of AgN₃ are 303.29 and 138.80 GPa.

Key words: AgN₃ and CuN₃ crystalline, Ab initio, Energy band structure, Electronic structure, Sensitivity, Elastic coefficients