First principles investigations and Hirshfeld surface analysis of high-energetic and low-sensitive 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) crystal

The high-energetic and low-sensitive explosive material of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was theoretically investigated by first principles calculations and Hirshfeld surface analysis. The experimental and partly optimized LLM-105 crystals were compared which indicated that it is important to correct the hydrogen positions. Hirshfeld surface analyses of the experimental and partly optimized LLM-105 crystals were also compared, which showed that the intermolecular H⋯O interactions significantly contribute to the stability of the LLM-105 crystal, while the contributions of other intermolecular interactions in the experimental and partly optimized LLM-105 crystals are quite different. The geometrical and electronic structures of LLM-105 molecules in the experimental and partly optimized crystals as well as that in the gas phase were compared. QTAIM analysis was employed to illustrate the existences of intermolecular interactions in the molecular pairs taken from partly optimized LLM-105 crystal, and the types of intermolecular interactions from QTAIM analysis are in agreement with the results of Hirshfeld surface analysis. The reason why the LLM-105 molecule in the partly optimized crystal adopts a non-coplanar structure in which the NO2 and NH2 groups is not coplanar with the six-membered ring is elaborated. The existence of cooperativity among different intermolecular interactions were verified by analysing the trimeric complexes formed among three LLM-105 molecules in the partly optimized crystal.