Molecular dynamics study of composition-dependent intermolecular interactions and trigger-bond stability in DNTF/HMX...

Intermolecular compatibility governs the cohesive and mechanical response of DNTF/HMX melt-cast explosive mixtures, but its composition dependence remains incompletely resolved. Among six mass ratios, 41:59 showed the highest normalized binding energy and cohesive energy density (1.853 × 10⁹ $\text{J}\bullet {\text{m}}^{-3}$ ) and the largest number of heteromolecular C-H···O contacts (342). Three representative dimers exhibited a mean counterpoise-corrected interaction energy of - 12.5 $\text{kJ}\bullet {\text{mol}}^{-1}$ . Electrostatic-potential and reduced-density-gradient analyses supported weak C-H···O contacts within a diffuse noncovalent field. The 31:69 system had the highest Pugh ratio (2.41) and Poisson's ratio (0.32), whereas 41:59 retained high values (2.34 and 0.31) together with the strongest cohesion. HMX N-NO₂ distributions were composition-insensitive, while the 41:59 environment suppressed the long-bond tails of DNTF C-NO₂ and N-O distributions. Thus, 41:59 provided the most favorable balance between heteromolecular cohesion and deformation adaptability within an equilibrium, nonreactive model.

Periodic DNTF/HMX amorphous models spanning 21:79-71:29 mass ratios were constructed in Materials Studio 2020 and simulated at 298-398 K with COMPASS II. Binding energy, cohesive energy density, radial distribution functions, geometric C-H···O contacts, elastic parameters, and trigger bond length distributions were evaluated. Finite-size effects were assessed using 5120, 10,240 and 20,480 atom models. Representative dimers extracted from the 41:59 trajectory were evaluated using the DMol³ module in Materials Studio 2020, from which counterpoise-corrected interaction energies and ESP surfaces were obtained. Wavefunctions for RDG analysis were generated using Gaussian at the B3LYP-D3(BJ)/6-311G(d,p) level and subsequently analyzed with Multiwfn.