Theoretical insights into the structures and fundamental properties of pnictogen nitrides

Abstract Recent experimental advancements reported a chemical reaction between antimony and nitrogen under high temperature and high pressure, yielding crystalline antimony nitride (Sb 3 N 5 ) with an orthorhombic structure. Motivated by this statement, we calculate the stability, elastic properties, electronic properties and energy density of the Cmc 2 1 structure for pnictogen nitrides X 3 N 5 ( X = P, As, Sb, and Bi) using first-principles calculations combined with particle swarm optimization algorithms. Calculations of formation enthalpies, elastic constants and phonon spectra show that P 3 N 5 , As 3 N 5 and Sb 3 N 5 are thermodynamically, mechanically and kinetically stable at 35 GPa, whereas Bi 3 N 5 is mechanically and kinetically stable but thermodynamically unstable. The computed electronic density of states shows strong covalent bonding between the N atoms and the phosphorus group atoms in the four compounds, confirmed by the calculated electronic localization function. We also calculate the energy densities for Sb 3 N 5 and find it to be a potentially high-energy-density material.