Recoverable high-energy compounds by reacting methane and nitrogen under high pressure

The search for the stable polymeric forms of solid nitrogen is of great importance in view of its potential application as a high-energy-density material. Using first-principles calculations combined with an effective crystal structure search method, we demonstrate that nitrogen can react with methane under relatively moderate pressures. The structures and the stability strongly depend on the composition. CN₂H₄ and CN₄H₄ compounds become stable in Pca2₁ and I-42d phases under pressures of 11 and 41 GPa, respectively. Especially, CN₄H₄ is recoverable as a metastable high energy material at ambient condition, and can release enormous amount of energy (6.430.28em0exkJ0.28em0exg^-1) while decomposing to molecular nitrogen and methane.