The Crystalline Form of 1,3,5,7-Tetranitro-1,3,5,7-Tetrazacyclooctane (Hmx)

The absorption spectra and dielectric constants of three of the four polymorphs of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) have been examined. The difference in absorption frequencies shows that these crystal forms are more distinctive than are most polymorphs. Likewise the distortion polarizations of HMX-I, -II, and -III are markedly different whereas identical distortion polarizations have been found among typical polymorphic systems. The distortion polarizations of HMX-II and -III also are unique because they are appreciably temperature dependent, although this electrical property ought to be temperature independent. Because of these unique behaviors we have postulated that the so-called HMX polymorphs actually are lattice-caged conformational modifications.