Crystal and molecular structures of ε-HNIW

There is a growing interest in HNIW (Hexanitrohexaazaisowurtzitane, CL-20) preparedby Nielsen in 1987. It is said that its explosive properties are superior to those ofOctogen (HMX), the best high explosive at present. Its application will improve perfor-mance characteristics of conventional weapons. HNIW at ambient pressure and temperatureexists in four polymorphic modifications:α,β,γand ε. Among them ε-HNIW possessesthe highest crystal density. We report for the first time the crystal and molecular structuresof the title compound.