First principle study and Hirshfeld surface analysis on the effect of type, number, and position of small molecules on the structural stability and optical property of a powerful energetic crystal 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide

Abstract

In the present study, the detailed functions of three small molecules, H₂O, NH₃, and H₂S, on the structural stability of a novel high energy compound 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) with high application value were investigated by the first principle study and Hirshfeld surface analysis. The effects of type, number, and position of small molecules on the molecular, crystal and electronic structures, close contacts and sensitivity, and optical properties of ICM-103 were also studied. First, the relatively high sensitivity feature used as initiating explosives of ICM-103 was confirmed, but H₂O, NH₃, and H₂S all could stabilize the structure of ICM-103 to reduce sensitivity by enhancing close contacts such as hydrogen bonding and increasing the ratio of red dots located on the block edge of Hirshfeld surface. This function could be further improved with the increment of number, and small molecules in two different positions were found to have a synergistic effect on stabilizing the structure. The stabilization ability of NH₃ was found to be stronger than H₂O and H₂S due to the highest stabilization energy and strongest close contacts. Then, H₂O and NH₃ reduced the absorption intensity to ultraviolet light but enhanced the absorption to visible light and infrared light. Three molecules all increased the dielectric constant and static refractive index with the order of H₂S, and H₂O, NH₃. NH₃ eliminated the region, in which light could not be transmitted in other crystals. Finally, the position of NH₃ was found to have significant effects on the structure and properties of ICM-103, while this is not obvious for H₂O and H₂S.