Determination of enthalpies of formation of energetic molecules with composite quantum chemical methods

Interpretable Performance Models for Energetic Materials using Parsimonious Neural Networks

Predictive models for the performance of explosives and propellants are important for their design, optimization, and safety. Thermochemical codes can predict some of these properties from fundamental quantities such as density and formation energies that can be obtained from first principles. Models that are simpler to evaluate are desirable for efficient, rapid screening of material screening. In addition, interpretable models can provide insight into the physics and chemistry of these materials that could be useful to direct new synthesis. Current state-of-the-art performance models are based on either the parametrization of physics-based expressions or data-driven approaches with minimal interpretability. We use parsimonious neural networks (PNNs) to discover interpretable models for the specific impulse of propellants and detonation velocity and pressure for explosives using data collected from the open literature. A combination of evolutionary optimization with custom neural networks explores and trains models with objective functions that balance accuracy and complexity. For all three properties of interest, we find interpretable models that are Pareto optimal in the accuracy and simplicity space.

Synthesis, Characterization and DFT Study of a New Family of High-Energy Compounds Based on s-Triazine, Carborane and Tetrazoles

An efficient one-pot synthesis of carborane-containing high-energy compounds was developed via the exploration of carbon-halogen bond functionalization strategies in commercially available 2,4,6-trichloro-1,3,5-triazine. The synthetic pathway first included the substitution of two chlorine atoms in s-triazine with 5-R-tetrazoles (R = H, Me, Et) units to form disubstituted tetrazolyl 1,3,5-triazines followed by the sequential substitution of the remaining chlorine atom in 1,3,5-triazine with carborane N- or S-nucleophiles. All new compounds were characterized by IR- and NMR spectroscopy. The structure of four new compounds was confirmed by single crystal X-ray diffraction analysis. The density functional theory method (DFT B3LYP/6-311 + G*) was used to study the geometrical structures, enthalpies of formation (EOFs), energetic properties and highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies and the detonation properties of synthesized compounds. The DFT calculation revealed compounds processing the maximum value of the detonation velocity or the maximum value of the detonation pressure. Theoretical terahertz frequencies for potential high-energy density materials (HEDMs) were computed, which allow the opportunity for the remote detection of these compounds.

Computational study of energetic derivatives of 3,3′-bridged ditriazoles

A series of energetic bridged ditriazole was designed by incorporating different bridges and substituents into 4H-1,2,4-triazole ring. The geometrical structures, heats of formation, detonation properties, electronic structures, thermodynamic properties, free spaces, impact sensitivities, and thermal stabilities of the designed compounds were evaluated by employing density functional theory. The results elucidate that the –N3 substituent and –N=N– bridge can sufficiently increase their heats of formation. The calculated values of detonation properties show that –NF2, –ONO2, –O–, and –N=N(O)– are useful structural fragments to improve their detonation performance. The incorporation of the oxy (–O–) bridge increases their HOMO–LUMO energy gaps. An analysis of h50 values indicate that most of the designed compounds are less sensitive. The N(ring)-NO2 bond in the majority of the derivatives may be a possible trigger bond in thermal decomposition process. The incorporation of –CH2–CH2– and –O– is helpful to enhance their thermal stabilities. Based on appropriate thermal stabilities and superb detonation properties, six compounds were screened as promising high energy density compounds.