High-pressure structural, mechanical, and vibrational properties of NAPTO: The first fused-ring energetic material with a 2D layered structure

Understanding the structural-property relationship under extreme conditions is important for energetic materials. Herein, the effects of pressure on the structural, mechanical, and vibrational properties and molecular interactions of the first fused-ring energetic material with a 2D layered structure, 4-nitro-7-azido-pyrazol-[3,4-d]-1,2,3-triazine-2-oxide (NAPTO), are determined using density functional theory calculations. The simulated crystal lattice parameters within dispersion corrected scheme are in good agreement with experiment at ambient condition. Also, the elastic constants and mechanical properties were studied in the pressure range of 0–25 GPa. It is found that the ductility, stiffness, and deformation resistance of solid NAPTO are enhanced due to the intensified atom-atom contacts and hydrogen bond interactions under pressure, which is also confirmed by the Hirshfeld surface and 2D-fingerprint plot analysis. Furthermore, based on the hydrogen bond coordination relaxation theory, the pressure-induced frequency shifts of the N–H stretching vibrational modes which marks hydrogen bonding were discussed as well.