Crystal structure and electronic properties of the new structure dinitride–nitride N₂MN (M: Cu, Ag)

Abstract

Copper and nitrogen compounds and silver and nitrogen compounds have been researched with the first‐principle linear combination of the atomic orbitals in full‐screen basis with the local gradient and hybrid potential of the density functional theory (DFT) realized in the CRYSTAL09 program code. We have found the structural N2MN (M: Cu, Ag) dinitride–nitride phase having an orthorhombic structure, the spatial group of the Ibam symmetry and four formula units in the primitive cell that have not been reported before. The structure was found to be layered, the metal atoms are linearly circled by the nitride N atoms, whereas, the other two atoms make a molecule with a small negative charge of ∼0.02 e. The volume elastic modules in N2CuN, N2AgN crystals are equal to 4.3 and 6.6 GPa, respectively, and their pressure derivatives are equal to 6.7 and 5.3, respectively. The electron energy spectrum makes a superposition of weakly interacting molecular states of N2 and metal states of MN. The bandgap width equals ∼0.05 eV. The estimations of the enthalpy energies show that N2MN possess large energy content and in its decomposition into metal and gaseous nitride the energy release can reach 8 eV cell−1, which appears to be higher than that in the known metal azides. Thus, the new structure of the dinitride–nitride N2MN combines the properties of molecular and semiconductor crystals: high compressibility, strong mechanical anisotropy, localized vacant states in the zone spectrum, and small bandgap. The unique physical properties can ensure their application as energy materials, the source of chemically pure nitride, and in semiconductor and optical material science.