A unified model of impact sensitivity of metal azides

Abstract

A comprehensive theoretical study of 18 metal azides is reported. Herein, the first theoretical model of impact sensitivity is developed which can safely distinguish sensitive and insensitive (alkali) metal azides. The model includes four solid-state criteria and three features of isolated atoms and molecules. Using ten azides with experimentally known crystal structures, we obtained the values of sensitivity function Ω which correlates well (R² = 0.91) with experimental impact energies. When three azides with a predicted crystal structure are added, the correlation becomes slightly poorer (R² = 0.84), but it still predicts alkali metal azides to be insensitive. Thus, the impact energies for sensitive azides lie in the range of 1–16 N cm⁻², while the predicted values for alkali metal azides lie in the range of 40–87 N cm⁻². Theoretical background for the proposed model of impact sensitivity is discussed in the paper.