Prediction of Gadolinium Polynitrides at High Pressures as High-Energy-Density Materials

Pressure-induced nitrogen-rich compounds hold significant application prospects in high-energy-density materials. Utilizing first-principles calculations and swarm-intelligence structure search methods, we have identified ten new types of Gd-N compounds with different configurations, such as one-dimensional N-chains composed of N₆ rings or N₈ rings, and two-dimensional N-layers constructed of N₁₄ rings, N₁₈ rings, or N₁₈ + N₆ rings. Moreover, the predicted Gd-N compounds exhibit different magnetic properties, and a magnetic phase diagram is constructed in the pressure range of 0 to 200 GPa. Remarkably, the volumetric energy density (11.58-17.79 kJ/cm³) of Gd polynitrides with high nitrogen content, including <i>P</i>-1(I)-GdN₆, <i>P</i>-1(II)-GdN₆, <i>R</i>-3-GdN₈, <i>C</i>2<i>mm</i>-GdN₉, and <i>P</i>1-GdN₁₀, surpassed that of TNT (7.05 kJ/cm³), making them promising candidates for energetic materials. The discovery of diverse chain-like and layered structures in the GdN<i>_x</i> compounds highlights the role of gadolinium in inducing the diversity and complexity of nitrogen arrangements.