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

Two high-pressure stable phases ( I 4 1 / a -CeN 4 and R 3̅ m -CeN 6 ) and two metastable phases ( P 6 mm -CeN 14 and P 6 mm -CeN 17 ) were proposed in Ce-N compounds at 150-300 GPa. The polymeric nitrogen units include quadruple helical chains, N 6 rings, and first reported layered molecular sieves structures. I 4 1 / a -CeN 4 can be quenched to ambient conditions and its thermal stability can be maintained up to 500 K. P 6 mm -CeN 14 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 sp 3 hybridized layered molecular sieve to enhance the stability of P 6 mm -CeN 14 . Surprisingly, the energy density (8.45 kJ/g) and explosive performance of P 6 mm -CeN 14 are the highest among all metal polynitrides, refreshing a new record for high-energy metal polynitrides.