Screening Nitrogen‐Rich Bases and Oxygen‐Rich Acids by Theoretical Calculations for Forming Highly Stable Salts

Nitrogen‐rich heterocyclic bases and oxygen‐rich acids react to produce energetic salts with potential application in the field of composite explosives and propellants. In this study, 12 salts formed by the reaction of the bases 4‐amino‐1,2,4‐trizole (A), 1‐amino‐1,2,4‐trizole (B), and 5‐aminotetrazole (C), upon reaction with the acids HNO₃ (I), HN(NO₂)₂ (II), HClO₄ (III), and HC(NO₂)₃ (IV), are studied using DFT calculations at the B97‐D/6‐311++G** level of theory. For the reactions with the same base, those of HClO₄ are the most exothermic and spontaneous, and the most negative Δ_rG_m in the formation reaction also corresponds to the highest decomposition temperature of the resulting salt. The ability of anions and cations to form hydrogen bonds decreases in the order NO₃^?>N(NO₂)₂^?>ClO₄^?>C(NO₂)₃^?, and C⁺>B⁺>A⁺. In particular, those different cation abilities are mainly due to their different conformations and charge distributions. For the salts with the same anion, the larger total hydrogen‐bond energy (E_H,tot) leads to a higher melting point. The order of cations and anions on charge transfer (q), second‐order perturbation energy (E₂), and binding energy (E_b) are the same to that of E_H,tot, so larger q leads to larger E₂, E_b, and E_H,tot. All salts have similar frontier orbitals distributions, and their HOMO and LUMO are derived from the anion and the cation, respectively. The molecular orbital shapes are kept as the ions form a salt. To produce energetic salts, 5‐aminotetrazole and HClO₄ are the preferred base and acid, respectively.