Simulation Calculation And Solvation Effect Study Of Ammonium Dinitramide Cocrystal

Ammonium dinitramide(ADN)is a high energy density material with potential applications,characterized by positive oxygen balance,high heat of formation,and high combustion rate.However,its hygroscopic nature affects its performance.Theoretical calculation methods were used to study the application of cocrystal technology in reducing the hygroscopicity of ADN.A simulation calculation method for energetic materials cocrystals was developed,and the properties of ADN cocrystals and the solvation effect were examined.The simulation calculation method for energetic cocrystals was proposed.Firstly,using binding energy calculation method to study the strength of interaction between cocrystal main and guest molecules at different mole ratios and obtain the ratio of the most stable cocrystal composition.Then,the radial distribution function and non-bonded interaction analysis were used to investigate whether there is a driving force for cocrystal formation between the main and guest molecules.Finally,the stability ratio obtained from the binding energy calculation was used to calculate the intermolecular site pair energy between molecules based on the molecular surface electrostatic potential to determine the feasibility of cocrystal formation.The comparison with existing experimental research results indicates that the established theoretical calculation method is effective and accurate.Using the above-mentioned energetic cocrystal simulation calculation method,the ADN/3,5-diamino-1,2,4-triazole(DAT)and ADN/2,2-dinitroethene-1,1-diamine(FOX-7)cocrystal were systematically studied,and the ADN/DAT and ADN/FOX-7 cocrystal ratios were determined to be 1:2.The cocrystal structure and morphology were predicted,and the densities of ADN/DAT cocrystal and ADN/FOX-7 cocrystal were calculated to be 1.76 and1.88 g/cm~3.At 20 ~oC and 40%relative humidity,the moisture absorption of the cocrystals decreased to 2.850%and 3.207%respectively compared to the saturated moisture absorption of 14.554%for the ADN crystal.The mechanism of moisture absorption prevention was investigated and it was found that cocrystal reduces the proportion of hydrophilic groups on the crystal surface and reduces hygroscopicity.To reveal the effect of solvents on the ADN-based cocrystal crystallization process,the solvation effect of the cocrystal was studied using the modified attachment energy model,and the relative growth rates of important crystal faces of the cocrystal in different solvents were simulated and calculated,and the crystal morphology and surface proportions were predicted.The adsorption of different solvent molecules on each crystal surface was analyzed.The results showed that the ADN-based cocrystal is significantly influenced by polar solvents,with higher hygroscopicity when crystallized in polar solvent environments,and lower hygroscopicity when crystallized in non-polar solvents.This work provides theoretical support and technical guidance for the preparation of low-hygroscopic ADN-based cocrystal products.