Heat of formation prediction by G4MP2-SFM schemes: An application to various nitroazole derivatives

Our G4MP2-SFM parameterization schemes have been applied to the various azole derivatives including imidazole, triazole, tetrazole, imidazolidine, [1,2,4]triazolo[4,3-a][1,3,5]triazine, tetrazine and pyrimidine, in order to establish a set of parameters for the reliable and fast heat of formation (ΔH_f ^o) predictions. It is shown that a parameterization on such complex systems is possible, yielding an overall mean absolute deviation (MAD) and root mean square deviation (RMSD) to be 3.5 kcal/mol and 4.3 kcal/mol, respectively compared to full G4MP2. During the development of the parameters, we have found that nonbonded interactions are very important to predict the ΔH_f ^o of high energy materials (HEMs). While both molecular weight and the number of NO₂ substituents rarely affect the ΔH_f ^o magnitude, the geometric configurations and the number of heteroatoms in the azole ring significantly change it.