Polymeric nitrogen in a graphene matrix: An ab initio study

A hybrid material where polymeric nitrogen chains are sandwiched between graphene sheets in the form of a three-dimensional crystal, is predicted by means of ab initio simulations. It is demonstrated that chainlike polymeric nitrogen phase becomes stable at ambient pressure when intercalated in a multilayer graphene matrix. The physical origin of this stabilization is identified by studying the electronic properties of the system. This approach of stabilizing polymeric nitrogen by means of external three-dimensional matrix constitutes a path toward synthesizing different types of nitrogen-based high-energy materials.

Figure 1

(Color online) Left: the unit cell of the ${\text{N}}_8$@graphene crystal structure, doubled in the stacking direction, as well as in the direction of the nitrogen chain periodicity. Right: the same system viewed from the stacking direction, showing the configuration of the planar nitrogen chain. The graphene sheet is represented schematically for sake of clarity.

Figure 2

(Color online) Band structure of isolated graphene sheet (left), isolated nitrogen chain (center), and the ${\text{N}}_8$@graphene system, plotted along the periodicity direction of the nitrogen chain. The zero of energy corresponds to the Fermi level for each system. The central panel shows the squared wave functions for valence-band maximum and conduction-band minimum of standalone nitrogen chain.

Figure 3

Electronic DOS for the ${\text{N}}_8$@graphene system, as well as for the isolated graphene sheet and nitrogen chain. DOS, projected on the orbitals of graphene and nitrogen chain is shown for the ${\text{N}}_8$@graphene structure. A 0.05 eV broadening is used.

Figure 4

(Color online) Electronic density redistribution upon intercalation of the N chain into the graphene matrix. Accumulations of positive and negative charges are shown with red and blue color, respectively.