Computational Discovery of New High-Nitrogen Energetic Materials

Abstract

High-nitrogen-content energetic compounds containing multiple N–N bonds are an attractive candidate for new generation of environmentally friendly, and more powerful energetic materials. High-N content translates into much higher heat of formation resulting in much larger energy output, detonation pressure, and velocity upon conversion to large amounts of non-toxic, strongly bonded $\text {N}_{2}$ gas. This chapter describes recent advances in the computational discovery of a new family of polynitrogen pentazolate compounds using powerful first-principles evolutionary crystal structure prediction methods. After description of the methodology of the first-principles crystal structure prediction, several new high-nitrogen-content energetic compounds are described. In addition to providing information on structure and chemical composition, theory/simulations also suggests specific precursors, and experimental conditions that are required for experimental synthesis of such high-N pentazolate energetic materials. To aid in experimental detection of newly synthesized compounds, XRD patterns and corresponding Raman spectra are calculated for several candidate structures. The ultimate success was achieved in joint theoretical and experimental discovery of cesium pentazolate, which was synthesized by compressing and heating cesium azide $\text {CsN}_{3}$ and $\text {N}_{2}$ precursors in diamond anvil cell. This success story highlights the key role of first-principles structure prediction simulations in guiding experimental exploration of new high-N energetic materials.