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 N rings or N rings, and two-dimensional N-layers constructed of N rings, N rings, or N + N 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/cm) of Gd polynitrides with high nitrogen content, including -1(I)-GdN, -1(II)-GdN, -3-GdN, 2-GdN, and 1-GdN, surpassed that of TNT (7.05 kJ/cm), making them promising candidates for energetic materials. The discovery of diverse chain-like and layered structures in the GdN compounds highlights the role of gadolinium in inducing the diversity and complexity of nitrogen arrangements.