New procedures to estimate the impact sensitivity of energetic materials are derived from an earlier semiempirical model correlating the drop weight impact height h50 to the rate constant k for the propagation of the decomposition process, assumed to be the limiting step. The new models are obtained by removing step by step the empiricism in the evaluation of k. We end up with a full ab initio expression for this constant in terms of theoretical activation energies and prefactors. The resulting model casts doubt on a previously introduced assumption regarding the temperature at the reaction front. Moreover, it questions possible interpretations of semiempirical estimates. A systematic comparison against alternative methods shows that although somewhat less accurate than its earlier semiempirical version, this ab initio model shows a predictive value similar to heavily parameterized approaches. The results imply that the decomposition kinetics accounts for at least 50% of the variation in the logarithms of drop height data.

This chapter reviews sensitivity correlations assuming initiation to be thermal in nature. A first group focuses on the thermal onset of chemistry, either considering only the first bond breaking events or accounting for more details of the mechanism. A second group assigns a prominent role to the propagation of the decomposition. Finally, a two-states model predicting the initiation probability as a function of the magnitude of the load is outlined.

Due to their lack of maturity, models for evaluating sensitivities from molecular structure have so far been relatively little used for the design of new energetic materials. The selection of molecules of potential interest is mostly driven by theoretical performances, which can be evaluated on the basis of well-established procedures. However, given the tremendous costs associated with experimentation involving such hazardous compounds, there is a clear interest in estimating relevant sensitivity criteria first. This chapter reviews practical aspects associated with the implementation of sensitivity models in a production setting, showing how to leverage the limited amount of data typically available to energetic material designers in view of obtaining reasonable sensitivity estimates for novel synthesis targets.