Edge Exposure as the Trigger for Structural Instability in LP-N and HLP-N

LP-N and HLP-N are promising high-energy-density materials. However, these materials synthesized under high pressure cannot be maintained stable at ambient conditions. The mechanism behind their instability remains unclear. Our research, based on first-principles calculations and ab initio molecular dynamics simulations, reveals that while not edge exposed, LP-N and HLP-N exhibit substantial structural, dynamic, and mechanical stability under ambient conditions. The stability of HLP-N is governed by an interlocking mechanism, which becomes ineffective upon exposure of the edges, leading to internal breakdown. As a result, H saturated adsorption has no impact on it. In contrast, LP-N benefits modestly from H saturated adsorption due to its edge-initiated dissociation. The interlocking mechanism offer valuable insights into the design of new materials.