Novel rubidium poly-nitrogen materials at high pressure.

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Chemistry

Background:

• High-pressure synthesis and characterization of novel energetic materials are crucial for energy storage and explosives.
• Rubidium-nitrogen compounds are underexplored, particularly under extreme conditions.

Purpose of the Study:

• To predict novel rubidium poly-nitrogen materials at high pressures using computational methods.
• To determine the stability and structural properties of these predicted compounds.
• To identify potential synthesis pathways and experimental signatures.

Main Methods:

• First-principles crystal structure prediction via high-throughput computational screening.
• Density Functional Theory (DFT) calculations for structural and energetic stability.
• Thermodynamic stability analysis and phase diagram prediction.
• Calculation of Raman spectra to aid experimental identification.

Main Results:

• Discovery of three novel rubidium poly-nitrogen compounds: RbN5, RbN2, and Rb4N6.
• Rubidium pentazolate (RbN5) predicted to be thermodynamically stable above 30 GPa, featuring aromatic cyclo-N5- anions.
• Synthesis of RbN5 is proposed via compression of RbN3 and N2 above 9.42 GPa, with characteristic Raman spectral features identified.
• RbN2 and Rb4N6, stable above 60 GPa, contain infinite nitrogen chains and N6 hexazine rings, respectively.
• A 1:1 RbN compound (Rb3N3) with bent N3 azide units was also predicted at high pressures.

Conclusions:

• First-principles calculations successfully predict novel, nitrogen-rich rubidium compounds stable under high pressure.
• The predicted compounds, particularly RbN5, offer new avenues for energetic materials research.
• Computational predictions, including Raman spectra, can guide experimental synthesis and verification of new materials.