To calculate the performance of energetic salts by applying thermo-chemical codes, new theoretical tools are required to predict their densities and formation enthalpies. The density of salts is evaluated using new models based on volume additivity. First, an existing group additivity method for neutral compounds has been extended to ionic crystals. Then, a more general approach has been developed. The solid-phase formation enthalpy Delta H-f degrees is evaluated using two distinct calculations for the contribution Delta H-f degrees(g) of isolated species on one hand, and the lattice energy E-latt on the other hand:Delta H-f degrees = Delta H-f degrees(g) - E-latt - 2RT (1)A procedure previously developed for neutral molecules and based on density functional theory (DFT) yields surprisingly good estimates of Delta H-f degrees(g) for simple isolated ions. Moreover, the lattice energy of organic ionic crystals proves to be approximately equal to the coulomb contribution E-coul. Taking advantage of this finding in the case of nitrate salts, a simple two-parameter equation may be used to correlate theoretical E-coul values with SCC-DFTB Mulliken charges. Alternatively, the lattice energy may be derived from a systematic packing of salt crystals.

Decomposition temperatures have been compiled for a set of 24 compounds including nitroalkanes, nitramines and nitric esters. In an attempt to rationalize their values, correlations involving either the dissociation energy for the weakest bond in the molecule or the proportion of trigger linkages are investigated. The latter quantity correlates fairly well with thermal stabilities. A simple model based on kinetic parameters associated with the breaking of trigger linkages allows the estimation of decomposition temperatures with an average absolute deviation from experiment < 11 ∘C and no error > 30 ∘C, except two outliers with errors ≃ 70–80 ∘C. The latter are associated with nitramines bearing esters or furazan moieties, which prove less stable than expected on the basis of their number of trigger linkages.

Solid-state formation enthalpies of energetic materials and related compounds are estimated from the difference between the calculated gas-phase formation enthalpies and sublimation enthalpies. The rms deviation from the observed values is 0.21 kJ/g using the most accurate method. The errors mostly depend on the limitations of the methods available to calculate the gas-phase contribution. For instance, the rms deviation increases by approximately 0.15 kJ/g on going from Density Functional Theory (DFT) to semi-empirical methods for this purpose.

Sensitivity prediction is a complex problem. Many studies attempted to correlate experimental data with molecular and microscopic features. In the context of the well‐recognized macroscopic hot spot model, an application of an original approach to predict impact sensitivity of 11 explosives is described in terms of parameters of explosive decomposition. This model provides a useful tool in the research for new explosives and the results do not depend on the calculation of solid‐state formation enthalpy of explosives.

A computational approach to nonadiabatic interband transitions in solids is outlined, with applications to energetic materials or semiconductors in view. The description of transition rates in terms of the time-dependent electronic wavefunction is discussed and numerical results obtained for ID clusters are presented. It is pointed out that the main limitations of the present model are due to the lack of a proper account of environmental effects.

It has been suggested that excited electrons might play a significant role in impact initiation of energetic materials, despite their very small number at thermal equilibrium and the lack of any detailed physical model to support such a view. Nonetheless, as pointed out in this paper, a compression wave may enhance excitations throught non-adiabatic processes. To study such effects, a computational approach is proposed.

Infrared spectra simulations require ab initio techniques to get reliable intensities. On the other hand, recent force fields can provide accurate molecular geometries and frequencies. Therefore, it is suggested that these new force fields could be used to simulate infrared spectra, dipole-moment surfaces being described at high levels of theory in order to get satisfactory intensities. As pointed out, for a system with N atoms, the cost of such a simulation would be reduced N-fold with respect to standard quantum approaches. Preliminary calculations based on this scheme are reported here. Encouraging results are obtained since no significant lost of accuracy is noted on going from the ab initio to the molecular mechanics potential energy surface. (C) 1998 John Wiley & Sons, Inc.

Some new approaches to computer-aided design of new energetic materials require highly efficient techniques to estimate relevant properties. To date, evaluation of the formation enthalpies makes a significant contribution to the computational cost when calculated with standard quantum mechanical techniques. In a quest for a more efficient procedure, the PIMM model is evaluated, as implemented in the 1991 version. According to present results, this method, while being roughly one order of magnitude more efficient than MNDO schemes for large molecules, is comparable to PM3 and far superior to AM1 with regard to the accuracy of calculated gas-phase enthalpies of formation.

The simulation of the energetic performances of explosive molecules requires the estimation of the heat of formation. A predictive approach has been used to calculate the molecular properties of the explosives with the semi-empirical AM1 method of quantum chemistry. To obtain the heat of formation in the condensed phase, either a global correction or a gradual one was used to study the two factors: accuracy of calculation of the heat of formation in the gas phase, and transition from the gas phase to the condensed phase. With the second procedure, precision is approximately +/-20%.