▪ Abstract  Energetic materials are chemical compounds or mixtures that store significant quantities of energy. In this review, we explore recent approaches to property prediction and new material synthesis. We show how the successful design of new energetic materials with tailored properties is becoming a practical reality.

We report the first quantum-based multiscale simulations to study the reactivity of shocked perfect crystals of the insensitive energetic material triaminotrinitrobenzene (TATB). Tracking chemical transformations of TATB experiencing overdriven shock speeds of 9 km/s for up to 0.43 ns and 10 km/s for up to 0.2 ns reveal high concentrations of nitrogen-rich heterocyclic clusters. Further reactivity of TATB toward the final decomposition products of fluid N(2) and solid carbon is inhibited due to the formation of these heterocycles. Our results thus suggest a new mechanism for carbon-rich explosive materials that precedes the slow diffusion-limited process of forming the bulk solid from carbon clusters and provide fundamental insight at the atomistic level into the long reaction zone of shocked TATB.

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We report Raman, infrared, and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid (FA) under pressure up to 50 GPa. We find an infinite chain Pna2(1) structure to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intrachain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of long-range order at pressures above 40 GPa, with a large hysteresis upon decompression. We attribute this behavior to a three-dimensional polymerization of FA.

We present the results of a quantum molecular dynamics simulation of the chemistry of HMX, a high performance explosive, at a density of 1.9 g/cm3 and temperature of 3500 K, conditions roughly similar to the Chapman−Jouget detonation state. The molecular forces are determined using the self-consistent-charge density-functional-based tight-binding method. Following the dynamics for a time scale of up to 55 ps allows the construction of effective rate laws for typical products such as H2O, N2, CO2, and CO. We estimate reaction rates for these products of 0.48, 0.08, 0.05, and 0.11 ps-1, respectively. We also find reasonable agreement for the concentrations of dominant species with those obtained from thermodynamic calculations, despite the vastly different theoretical underpinning of these methodologies.

Two nonrelativistic Born–Oppenheimer potential energy surfaces of the same space-spin symmetry may intersect on a surface of dimension N−2, where N is the number of internal nuclear degrees of freedom. Characterization of this entire surface can be quite costly. An algorithm, employing multiconfiguration self-consistent-field (MCSCF)/configuration interaction(CI) wave functions and analytic gradient techniques, is presented that avoids the determination of the full N−2 dimensional surface, while directly locating portions of the crossing surface that are energetically important. The algorithm determines extrema of the Lagrangian function LIJ(R,ξ,λ) = EI(R) + ξ1[EI(R) − EJ(R)] + ξ2HIJ(R)/2+ ∑Mk=1λkCk(R), where Ck(R) is any geometric equality constraint such as RKL2−αKL2=0, or RKL2−RMN2=0, RKL=‖RK−RL‖ and the ξ and λ are Lagrange multipliers. The efficacy of this algorithm is demonstrated using a MCSCF/first order CI description of 1,22A′ states of HCO.

The combined effect of pressure and molecular vacancies on the atomic structure and electronic properties of solid nitromethane, a prototypical energetic material, is studied at zero temperature. The self-consistent charge density-functional tight-binding method is applied in order to investigate changes induced in the band gap of this system by uniform and uniaxial strain of up to 70%, corresponding to static pressure in the range of up to 200 GPa. The effects of molecular vacancies with densities ranging from 3% to 25% have also been considered. A surprising finding is that uniaxial compression of about 25–40 GPa along the b lattice vector causes the C–H bond to be highly stretched and leads to proton dissociation. This event also occurs under isotropic compression but at much higher pressure, being indicative of a detonation chemistry which is preferential to the pressure anisotropy. We also find that the band gap, although evidently dependent on the applied strain, crystal anisotropy and vacancy density, is not reduced considerably for electronic excitations to be dominant, in agreement with other recent first-principles studies.

We report the existence of a novel C48N12 molecular structure to the recently reported thin-film formation of nano-onions of carbon and nitrogen with similar composition [Phys. Rev. Lett. 2001, 87, 225503]. An extended local aromaticity of eight all-carbon hexagonal rings is the driving force toward the maximum stability of this molecule, which is found to be 13.1 kcal/mol energetically more stable at the B3LYP/6-31G* level of theory than the recently reported structure [Chem. Phys. Lett. 2001, 340, 227]. The extended region of electron delocalization enhances the stability of this molecule via resonance energy contribution. On the basis of HUMO-LUMO gap of 2.74 eV, the new material is predicted to be an insulator.