Comparative study on structural and electronic response behaviors of three energetic materials containing tri-isomeric oxadiazole rings in electric field

Abstract

Context

High-energy-density materials (HEDMs) with balanced energy, stability, and safety are central to modern defense and civilian energetic applications. Among nitrogen-rich heterocyclic frameworks, oxadiazole rings stand out for their high formation enthalpy, oxygen balance, and structural tunability—making them ideal building blocks for next-generation energetic materials. However, the isomeric effect on molecular structure, electron distribution, and response to external stimuli (e.g., electric fields) remains poorly understood, despite its critical role in predicting sensitivity, detonation behavior, and environmental stability. In this study, the structural response and electronic properties of PA-1~PA-3 under an electric field were studied by a theoretical calculation system. The results showed the following: First, in terms of molecular structure response, PA-1 showed significant nonlinear changes, PA-2 only mutated at a specific field strength (0.010 a.u.) due to amino modification, while PA-3 maintained optimal stability by virtue of azide groups; second, the polarization characteristic analysis showed that the linear polarizability of PA-1 reached the peak at 0.020 a.u. field strength, PA-2 showed nonlinear behavior, and PA-3 showed the lowest sensitivity; third, weak interaction studies show that the C1 atom dominates the interaction of molecular fragments, and different functional groups significantly affect the electric field adaptability of materials; fourth, the electronic structure analysis revealed that PA-3 had the strongest resistance to an electric field, and its HOMO-LUMO energy gap had the smallest change. This study clarified the molecular mechanism of functional groups regulating the electric field response of materials and provided theoretical guidance for the design of new electric field response materials.

Method

Using density functional theory, the B3LYP/6–311+G(d, p) method was employed for structural optimization. After optimizing convergence, ensure that there are no imaginary frequencies to obtain a stable structure. Wave function analysis was performed using Multiwfn 3.8 and VMD 1.9.3. The EEF strength ranged from 0 to 0.02 a.u., with a growth gradient of 0.005 a.u.