Crystalline LiN5 Predicted from First-Principles as a Possible High-Energy Material.
The search for stable polymeric nitrogen and polynitrogen compounds has attracted great attention due to their potential applications as high-energy-density materials. Here we report a theoretical prediction of an interesting LiN5 crystal through first-principles calculations and unbiased structure searching techniques. Theoretical calculations reveal that crystalline LiN5 is thermodynamically stable at pressures above 9.9 GPa, and remains metastable at ambient conditions. The metastability of LiN5 stems from the inherent stability of the N5(-) anions and strong anion-cation interactions. It is therefore possible to synthesize LiN5 by compressing solid LiN3 and N2 gas under high pressure and quench recover the product to ambient conditions. To the best of our knowledge, this is the first time that stable N5(-) anions are predicted in crystalline states. The weight ratio of nitrogen in LiN5 is nearly 91%, placing LiN5 as a promising high-energy material. The decomposition of LiN5 is expected to be highly exothermic, releasing an energy of approximately 2.72 kJ·g(-1). The present results open a new avenue to synthesize polynitrogen compounds and provide a key perspective toward the understanding of novel chemical bonding in nitrogen-rich compounds.
†College of Physics and Electronic Information, Luoyang Normal University, Luoyang 471022, China.|⊥Beijing Computational Science Research Center, Beijing 10084, China.
Feng
F
Peng
‡Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada.|§Canadian Light Source, Saskatoon, Saskatchewan S7N 2 V3, Canada.
Yansun
Y
Yao
‡Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada.
Hanyu
H
Liu
∥State Key Lab of Superhard Materials, Jilin University, Changchun 130012, China.
Yanming
Y
Ma
high energy density materials; lithium-nitrogen complex; polynitrogens