Compressibility of Inorganic Azides

The compressibility of α lead azide, β lead azide, barium azide, potassium azide, sodium azide, and thallium azide have been measured by single-crystal x-ray diffraction techniques for the first time in a new application of the diamond anvil pressure cell. Both the anisotropic and volume compressibilities are reported. The pressures were determined by measurements at the known freezing points of n-hexane and ethanol. A phase transition occurs in thallium azide at a pressure between the freezing points of chloroform (5390 bar) and n-decane (2990 bar). Pressure–temperature observations in the diamond cell of lead azide were carried out to 300°C and approximately 30 kbar. No phase transitions were observed. Radiation damage to azide crystals under high pressures is reduced significantly.