Impact sensitivity of crystalline phenyl diazonium salts: A first-principles study of solid-state properties determining the phenomenon

Two crystalline salts, phenyl diazonium chloride (PDC) and tetrafluoroborate (PDT), were chosen as probes for theoretical study of solid-state properties responsible for impact sensitivity since these salts differ only in the nature of anion and, hence, in the properties of solid state. In the present report, we have studied the influence of electronic structure, vibrational spectra, mechanical properties, crystal growth morphology, and the stored energy content on impact sensitivity of PDC and PDT to find the most important solid state characteristics governing this phenomenon. The band structure calculations at various external pressures indicate very different response of the band gap. Extremely sensitive PDC crystals acquire the metallic nature at 29 GPa (metallization point), whilst in the PDT crystals the complete closure of band gap occurs only at 200 GPa. Moreover, the stored energy content in PDC is by 1000 kJ mol(-1) higher than that of PDT. Only these two properties among the calculated in the present work differ significantly in the studied crystals. The rest solid-state characteristics such as crystal packing, vibratial spectra (phonon-valence vibration energy transfer probability), elastic properties (bulk moduli) demonstrate rather close values. The influence of metallization point (GPa) as well as crystal growth morphology on impact sensitivity is discussed for the first time.