Fig. 1. (a) Formation enthalpies ΔH of various CeN_n (n = 0.5, 1, 2, 3, 4, 5, and 6) compounds under high pressure. The stable phases are connected by solid lines and unstable/metastable phases by dashed lines. (b) Pressure–composition phase diagram of the predicted Ce–N phases.

Fig. 2. (a) Crystal structure of P1̄-CeN₆ at 32 GPa. (b) Nitrogen structural skeleton of P1̄-CeN₆ at 32 GPa. The independent N atoms are marked as N1, N2, and N3 in the symmetric N₁₄ rings. (c) Phonon dispersion curve and PHDOS of P1̄-CeN₆ at 32 GPa. (d) Initial and terminal structures in AIMD simulations with total simulation time 10 ps and fluctuations of the total energy of P1̄-CeN₆ at 32 GPa and 300 K.

Fig. 3. (a) ELF of P1̄-CeN₆ (isovalue = 0.8). (b) The charge transfer and formation energy of CeN_n (n = 1, 2, 3, 4 and 6) compounds at 32 GPa.

Fig. 4. (a) Crystal structure, (b) −pCOHP and −ICOHP, and (c) PDOS of N₂ molecular crystal. (d) Crystal structure, (e) −pCOHP and −ICOHP, and (f) PDOS of trans-CeN₆. (g) Crystal structure, (h) −pCOHP and −ICOHP, and (i) PDOS of P1̄-CeN₆ at 32 GPa.

Fig. 5. (a) Phonon dispersion curve and PHDOS of P1̄-CeN₆ at 0 GPa. (b) RDFs g(r) and structures of final states from the last 2 ps of AIMD simulations at ambient pressure and temperatures of 300 K (solid lines) and 1000 K (dotted lines). (c) PDOS of P1̄-CeN₆ at 0 GPa. (d) Curves of charge transfer and enthalpy as functions of pressure during pressure release in P1̄-CeN₆, with the enthalpy of P1̄-CeN₆ at 32 GPa being taken as the reference zero point.

Fig. 6. (a) 3D surface and (b) 2D projected profiles of Young’s modulus in P1̄-CeN₆.

Table 1. Mass density ρ, mass energy density E_d, volumetric energy density E_v, detonation velocity V_d, and detonation pressure P_d of $P\bar{1}$-CeN₆ compared with those of TNT and HMX.

Table 2. Bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν, and Vickers hardness H_v of $P\bar{1}$-CeN₆.