Ab initio calculation of structural stability, electronic and optical properties of Ag₂Se

The structural stability, electronic and optical properties of Ag₂Se compound is studied using ab initio packages. Ag₂Se is found to crystallize in orthorhombic structure with two different space groups i.e. P2₁2₁2₁ (No. 19) and P222₁ (No. 17). For this compound in these two space groups, the total energy has been computed as a function of volume. Our calculated results suggest that the P2₁2₁2₁–phase is more stable than that of the P222₁–phase. The band structure calculation show that Ag₂Se is semimetallic with an overlap of about 0.014 eV in P2₁2₁2₁–phase whereas is metallic in nature in P222₁–phase. Moreover, the optical properties including the dielectric function, energy loss spectrum are obtained and analysed