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

Context

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.

Method

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.