High nitrogen polymer in silver polynitrides.

The Ag-N system is enriched by proposing four polymeric structures in first-principles calculations at high-pressure. The proposed P-1-AgN2 and P21/c-AgN2 not only break the new record in the polymeric configuration of MN2 compound, but also in the energy density. In the MN2 stoichiometric ratio, the infinite armchair-antiarmchair chain and the layered polymer structure are reported for the first time in P-1-AgN2 and P21/c-AgN2, indicating that the highly polymerised structure can also be formed in nitrides with low nitrogen content at high pressure. The mechanism of structure evolution behaviors of AgN2 under pressure is revealed by the analysis of atomic orbital hybridization. Meanwhile, the high energy densities are obtained in P-1-AgN2 (1.76 kJ/g) and P21/c-AgN2 (2.01 kJ/g) compared to all the reported MN2 nitrides. In addition, the infinite band-shaped structure and infinite curve layer structure are obtained in P-1-AgN5 and C2/m-AgN6, respectively. The energy densities of P-1-AgN5 (3.82 kJ/g) and C2/m-AgN6 (4.51 kJ/g) are comparable to or larger than that of TNT (4.3 kJ/g). Moreover, P-1-AgN2, P21/c-AgN2, P-1-AgN5, and C2/m-AgN6 exhibit excellent explosive performance in terms of detonation velocity and detonation pressure. .