A Novel Polymerization of Nitrogen in Beryllium Tetranitride at High Pressure

Abstract

The stable polymeric nitrogen and polynitrogen compounds have potential applications in high-energy-density materials. For beryllium nitrides, there is one known crystalline form, Be3N2, at ambient conditions. In the present study, the structural evolutionary behaviors of beryllium polynitrdes have been studied up to 100 GPa using first-principles calculations and unbiased structure searching method combined with density functional calculations. One stable structural stoichiometry of beyrllium polynitride has been theoretically predicted at high pressures. It may be experimentally synthesizable at high pressures less than 40 GPa. It is therefore possible to synthesize BeN4 by compressing solid Be3N2 and N2 gas under high pressure and BeN4 may be quenching recoverable to ambient conditions. The predicted high-pressure P21/c-BeN4 compound contains a novel variety of polynitrogen, extended polymeric 3D puckered N10 rings network. To the best of our knowledge, this is the first time that stable N10 rings network are predicted in alkaline-earth metal polynitrides. The decomposition of P21/c-BeN4 is expected to be highly exothermic, releasing an energy of approximately 6.35 kJ·g–1. The present results open a new avenue to synthesize polynitrogen compound and provide a key perspective toward the understanding of novel chemical bonding in nitrogen-rich compounds. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.