Theoretical Studies On Intermolecular Interaction Of S-tetrazine High-nitrogen Materials

S-tetrazine high-nitrogen compounds are new energetic materials (EMs) with bright prospects of applications developed in recent years, because of their higher positive enthalpy of formation, lower sensitivity, and good thermal stability. Moreover, high nitrogen low carbon hydrogen content in their structures makes them present high density and easily obtain oxygen balance.Intermolecular interactions have significant effects on many physical properties of EMs, such as diffusion, aggregation, density and detonation, and so on. In addition, Intermolecular interactions are also closely related to safety and mechanical properties of EMs. Therefor, there is an important academic and application significance to carry out studies on the intermolecular interactions of S-tetrazine high-nitrogen compounds.In this dissertation, by using density functional theory (DFT) B3LYP methods in Gaussian 98 package at 6-31G*,6-311G* and 6-311++G** basis sets, we investigated the intermolecular interactions of six S-tetrazine compounds:3,6-diamino-S-tetrazine dimers (DATZ)2,3,6-diamino-S-tetrazine-1,4-di-N-oxide dimers (LAX-112)2,3,6-dihydrazino-S-tetrazine dimers (DHT)2,3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-S-tetrazine dimers (BTATz)2,3,6-diguanidino-S-tetrazine dimers (DGTz)2,3,6-bis-nitroguanyl-S-tetrazine dimers (DNGTz)2, and 3,6-diamino-S-tetrazine-ammonia complexes (DATZ-NH3) 3,6-diamino-S-tetrazine-1,4-di-N-oxide-hydrogen-fluoride complexes [(LAX-112)-HF]. Fully optimized geometries of each system have been obtained with DFT method at their respective level; Vibrational frequencies were calculated to ascertain that each structure was characterized to be the minima on their potential energy surfaces(no imaginary frequencies); The intermolecular interaction energy was calculated with basis set superposition error (BSSE) correction and zero point energy (ZPE) correction; The charge redistribution and transfer was acquired through natural bond orbital (NBO) analysis, and which was performed to reveal the origin of the intermolecular interaction; The changes of thermodynamic properties from the monomer to complexes with the temperature ranging from 200.0 K to 800.0 K have been obtained using the statistical thermodynamic method; The relationship between the structure and properties of complexes was studied and the graded rules on changing from monomers to complexes were revealed.Theoretical studies on intermolecular interactions of S-tetrazine compounds shows:(1) Intermolecular interaction has more influence on molecular structure, sensitivity and stability; (2) The calculated results are in good agreement with the predecessors experimental ones, and complement with each other, which reflect the relationship between structure and properties of S-tetrazine compounds; (3) These results establish theoretical foundation for the formula design of explosive mixtures, and further extend the practical application areas of intermolecular interaction theory on high energy system.