Perspectives on the crystal densities and packing coefficients of explosive compounds

We have investigated possible relationships between four crystal properties: experimental densities and computed intrinsic molecular volumes, packing coefficients and amounts of free space per molecule in the crystal lattices. Our focus was upon C-, H-, N-, O-containing explosive compounds. The objectives were to gain some insight into how densities might be increased, to improve detonation performance, and the amounts of free space per molecule decreased, to counter one of the factors promoting undesired sensitivity to accidental stimuli. The issue of molecular planarity was also examined. The best correlation found between the four properties is perhaps a surprising one: The free space per molecule increases as the molecules are bigger. On the other hand, some relationships that seem to be intuitively reasonable turn out to be quite weak. The principal positive conclusions are that it is desirable for explosive compounds to be composed of molecules that are small and preferably planar.