Nitrides at ultra-high pressures: the Ca-N and Sr-N systems to 240 GPa

Polynitrogen (poly-N) compounds have been actively pursued driven by their potential as ultrahigh-performing propellants and explosives. Thus far, the binary systems' investigation for poly-N species was largely limited below 125 GPa, and never has the threshold above 200 GPa been breached—although theoretical calculations predict even more exotic N chemical arrangements to be synthesized. This proposal aims to explore the terra incognita that is poly-N chemistry in the multimegabar regime by probing laser-heated Ca-N and Sr-N systems up to 240 GPa, employing the single-crystal X-ray diffraction from the polycrystalline samples (SC-XRDp) technique for structural determination. Of great fundamental physicochemical interest, the discovery of novel high pressure poly-N species is also indispensable as targets for lower pressure syntheses.