High-pressure induced structural changes of energetic ionic salts: Dihydroxylammonium 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate (MAD-X1)

Abstract

Pressure-induced structural changes of dihydroxylammonium 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate (MAD-X1), an insensitive energetic ionic salt with high detonation performance, was investigated under simulated conditions (0 to 10 GPa). Using the first-principles density-functional theory, the geometrical structure, intra/intermolecular interactions, electronic properties and Raman spectrum were calculated in detail to elucidate material stability. The anisotropic compressibility in MAD-X1 was revealed by variations of lattice parameters. Furthermore, combining internal hydrogen bonds and geometric parameters of each moiety, we could explain the abrupt changes on lattice constants from two aspects, which demonstrated the contribution of hydrogen bonding to decreasing the material sensitivity. Studies on band gap and partial density of state showed that excessive pressure probably inhibit the electron transfer. Additionally, the simulation of vibrational properties suggested a possible phase transition at 7–8 GPa, implying that MAD-X1 could maintain its stability up to 7 GPa.