Two Ultrahigh-Energy-Density Layered Cerium Polynitrides with Molecular Sieve Channel.

ABSTRACT

Two high-pressure stable phases (I41/a-CeN4 and R3̅m-CeN6) and two metastable phases (P6mm-CeN14 and P6mm-CeN17) were proposed in Ce-N compounds at 150-300 GPa. The polymeric nitrogen units include quadruple helical chains, N6 rings, and first reported layered molecular sieves structures. I41/a-CeN4 can be quenched to ambient conditions and its thermal stability can be maintained up to 500 K. P6mm-CeN14 is dynamically and mechanically stable at ambient pressure. The electronic properties analyses show that charge transfer between the Ce and N atoms makes a significant contribution to the structural stability by promoting the formation of Ce-N ionic bond and N-N covalent bond. The Ce atom provides a suitable coordination environment and an excellent bonding state for the fully sp3 hybridized layered molecular sieve to enhance the stability of P6mm-CeN14. Surprisingly, the energy density (8.45 kJ/g) and explosive performance of P6mm-CeN14 are the highest among all metal polynitrides, refreshing a new record for high-energy metal polynitrides.