Theoretical insights into the structures and fundamental properties of pnictogen nitrides

Abstract

Abstract Recent experimental advancements reported a chemical reaction between antimony and nitrogen under high temperature and high pressure, yielding crystalline antimony nitride (Sb3N5) with an orthorhombic structure. Motivated by this statement, we calculate the stability, elastic properties, electronic properties and energy density of the Cmc21 structure for pnictogen nitrides X 3N5 (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 P3N5, As3N5 and Sb3N5 are thermodynamically, mechanically and kinetically stable at 35 GPa, whereas Bi3N5 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 Sb3N5 and find it to be a potentially high-energy-density material.