Nitrogen-rich GaN5 and GaN6 as high energy density materials with modest synthesis condition

Here, the energetic gallium nitrides with the network and zigzag poly-nitrogen configurations at modest pressures have been predicted. The nitrogen-rich Cmc21-GaN5, high-pressure P21/m-GaN5 and C2/c-GaN6 phases can release higher energy of ∼3.27 kJ g−1, 4.12 kJ g−1, 5.71 kJ g−1, respectively, which are close to or even higher than that of the traditional high energy density materials TNT and possess distinguished detonation performance simulated. The predicted synthesis pressures of GaN5 and GaN6 (25 and 50 GPa) are much lower than that of the famous atomic cg-N. The VSEPR theory and Zintl-Klemm concept are employed to reasonably explain the bonding properties of N-N bonds in locally environments. High pressures modulate the electron transfer between the different orbits and further induce higher energy density. The conjugation effect of π electrons in planar polymeric nitrogen chains is the main reason for the metallization of gallium nitrides.