Synthesis and Stability of High-Energy-Density Niobium Nitrides under High-Pressure Conditions

Area of Science:

• Materials Science
• Solid-State Chemistry
• High-Pressure Physics

Background:

• High-energy-density materials (HEDMs) are vital for energy storage and defense.
• Transition metal polynitrides show potential as advanced HEDMs.

Purpose of the Study:

• Investigate the crystal structures of niobium nitrides under high pressure.
• Identify novel high-pressure phases and their bonding characteristics.

Main Methods:

• Single-crystal synchrotron X-ray diffraction up to 120 GPa.
• Density Functional Theory (DFT) calculations.
• Raman spectroscopy.

Main Results:

• Observed stable niobium polynitrides NbN4 and NbN5 at 100-120 GPa.
• Identified low-order nitrogen bonding forming polynitrogen anions.
• Noted an increasing metal-nitrogen coordination number with pressure.

Conclusions:

• Niobium polynitrides exhibit unique structural and bonding properties at megabar pressures.
• These findings advance the understanding of HEDMs and nitrogen-rich materials.