First-principles studies of the structural, electronic and optical properties of dinitrides CN2, SiN2 and GeN2

We report first-principles calculations of the electronic properties of orthorhombic CN2, SiN2 and GeN2. We made a comparison of the lattice constants, elastic constants, bulk, shear, Young’s moduli, Poisson’s ratio and band gaps using different exchange–correlation functionals. Our calculations reveal that GeN2 is a high dielectric constant material with small band gap, while CN2 and SiN2 are wide band gap materials.