IrN₄ and IrN₇ as potential high-energy-density materials

Area of Science:

• Materials Science
• Inorganic Chemistry
• Computational Chemistry

Background:

• Transition metal nitrides exhibit unique crystal structures and diverse applications.
• High nitrogen content materials are of interest for their energetic properties.

Purpose of the Study:

• To predict novel, nitrogen-rich iridium nitride compounds.
• To investigate their structural stability, energetic properties, and mechanical characteristics.

Main Methods:

• First-principles swarm-intelligence structural searches were employed to predict new phases.
• Density Functional Theory (DFT) calculations were used to assess dynamic stability and mechanical properties.

Main Results:

• Two N-rich iridium nitrides, IrN4 and IrN7, were predicted under moderate pressure.
• Both compounds exhibit dynamic stability at ambient conditions, featuring IrN6 octahedrons linked by polynitrogen units.
• Calculated energy densities are 1.3 kJ/g for IrN4 and 1.4 kJ/g for IrN7.
• IrN4 demonstrates good tensile (40.2 GPa) and shear strengths (33.2 GPa), with a hardness of 20 GPa.

Conclusions:

• IrN4 and IrN7 are predicted to be stable, high energy density materials.
• Their synthesis under moderate pressure and recoverability at ambient pressure encourage experimental validation.