Ab initio calculations of structural, elastic, and electronic properties of silver nitrides

The all-electron approach implemented in the CRYSTAL06 program is used along with a pseudopotential method in the pseudo-atomic orbital basis set to study the crystal structure, elastic constants and bulk moduli, the band structure and density of states for the family of silver nitrides. Calculations are performed within density functional theory with the use of local and gradient functionals to describe exchange and correlation. For the general type of the cubic lattice, all considered compounds can be put in the following order of their relative stability: AgN (rock salt structure), AgN₂ (fluorite structure), Ag₂N (cuprite structure), and Ag₃N (anti-ReO₂). It is shown that AgN, AgN₂, and Ag₂N are metals, whereas Ag₃N is a semiconductor with a band gap of 0.25 eV. Chemical bonding in these compounds has ionic and covalent components, apart from the metal one.