High-Pressure Synthesis of the First Thermodynamically Stable Silver Nitride, AgN₅

Area of Science:

• High-pressure and high-temperature synthesis
• Inorganic chemistry
• Materials science

Background:

• Silver is a noble metal known for chemical inertness.
• Molecular nitrogen is typically unreactive due to its strong triple bond.
• No thermodynamically stable silver-nitrogen compounds were previously reported.

Purpose of the Study:

• To synthesize and characterize a novel silver-nitrogen compound.
• To investigate the stability of silver-nitrogen solids under extreme conditions.
• To explore the formation of nitrogen-rich compounds from inert elements.

Main Methods:

• Direct reaction of elemental silver with molecular nitrogen at 118(3) GPa and 2000(200) K.
• Synchrotron single-crystal X-ray diffraction (SCXRD) for crystal structure determination.
• Density functional theory (DFT) for enthalpy calculations, phonon, and electron band structures.

Main Results:

• Successfully synthesized silver pentazolate (AgN5) with a novel crystal structure.
• AgN5 is the only thermodynamically stable Ag-N solid between 10 and 120 GPa.
• DFT and SCXRD data provided insights into the stability range of AgN5 upon decompression.

Conclusions:

• High pressure and temperature can induce reactions between inert elements like silver and nitrogen.
• The formation of AgN5 demonstrates the potential for creating novel nitrogen-rich compounds.
• This work expands the known phase diagram of silver-nitrogen systems.