Investigating geometric structure, energies, electronic structure and impact sensitivity illustrated with surfaces of ε-CL-20

The sensitivity of energetic compounds is different from one crystal direction to another, known to be anisotropic. To explore the effects of different surfaces on impact sensitivity, we investigate the structural properties, energies, electronic structure and impact sensitivity of various surfaces of ε-Cl-20 based on the first-principles calculations, the surfaces including (0 0 1), (0 1 0), (0 1 1), (0 1 2), (0 2 1), (1 0 0), (1 0 1), (1 0 2), (1 1 0), (1 1 1), (1 2 0), (2 0 1) and (2 1 0). It turns out that there is a good correlation between the N–N average bond population (Y) versus average bond lengths (X). The (1 0 2) surface has the most extended N–N average bond length, the lowest average bond population, the most substantial excess energy, and lowest nitro group charge, which indicate that (1 0 2) surface has the maximum impact sensitivity compared to other surfaces. There is a clear trend for band gap to decrease as excess energy becomes larger except (1 0 2) and (2 0 1) surfaces. The lower nitro group charge −Q_NO2 is, the more massive excess energy is, and the higher impact sensitivity is. The results indicate that the excess energy is regarded as a theoretical criterion of sensitivity to surfaces of ε-Cl-20.