Amorphous polymerization of nitrogen in compressed cupric azide

Metal azides have attracted increasing attention as precursors for synthesizing polymeric nitrogen. In this article, we report the amorphous polymerization of nitrogen by compressing cupric azide. The ab initio molecular dynamics simulations show that crystalline cupric azide transforms into a disordered network composed of singly bonded nitrogen at a hydrostatic pressure of 40 GPa and room temperature. The transformation manifests the formation of a π delocalization along the disordered Cu-N network, thus resulting in a semiconductor-metal transition. The estimated heat of formation of the amorphous polymeric nitrogen system is comparable to conventional high-energy-density materials. The amorphization provides an alternative route to the polymerization of nitrogen under moderate conditions.