Design and performance evaluation of nitrogen-rich bis-six-membered fused ring energetic materials via density...

Density functional theory (DFT) calculations at the M06-2X/def2-TZVP level were employed to design bis-six-membered nitrogen-rich fused ring energetic materials. Six neutral derivatives (I-2-4, I-3-4, I-3-5, II-2-4, II-3-4, and II-3-5) achieved energy densities exceeding 2.0 g/cm³, with energetic salts reaching unprecedented values up to 3.3 g/cm³. Non-covalent interaction isosurfaces quantified van der Waals forces in crystal packing, while decomposition pathway simulations for II-3-2 identified a low O-NO₂ BDE (20.24 kcal/mol) coexisting with high thermal stability ( $T_{\text{bp}}$ = 765.3 °C), governed by autocatalytic kinetics ( $\Delta G$ = 24.7 kcal/mol and $\Delta G$ = 8.44 kcal/mol). The DFT-derived performance matrix ( $\rho$ > 2.02 g/cm³, $T_{\text{bp}}$ > 600 °C, HOFs > 3500 kJ/mol) provides a transferable protocol for balancing energy and safety in molecular modeling of advanced energetics.

The DFT-based geometric optimization and frequency analyses of the designed molecules were determined using M06-2x/def2-TZVP method at Gaussian 09 package suite of programs. The heats of formation (HOF) for all molecules were obtained using an atomization reaction. The kinetic energy ( $\Delta E_{\text{HOMO}-\text{LUMO}}$ ), electrostatic potential (ESP), and other related calculations were computed using Multiwfn_3.8_dev software. The visualization of the weak interaction between dimers was accomplished using VMD 1.9.3 program.