Solvent Effects on the Crystal Morphology of Pentaerythritol Tetranitrate (PETN)

Controlling crystal morphology is important in many areas of science including drug manufacturing, single-crystal X-ray diffraction, and high explosive production. To understand the effects of solvent choice on the growth of the common explosive initiator PETN, we employed temperature-controlled crystallization in four solvents and two mixed solvents to observe the resulting crystal morphology. We further investigated the morphologies using established shape prediction models─the modified attachment energy model and the occupancy attachment energy model─as well as our modified surface energy model, presented here. We found that none of these energetic models accurately reproduce the observed morphologies, suggesting that predictions based solely on energetics are not always reliable and that there is a need to also consider kinetic and/or entropic effects. Lastly, we examined the effects of crystal morphology on subshock sensitivity through both traditional drop weight impact testing and the new VIPIR test. The confounding results highlight the need to consider multiple testing options when evaluating the effects of morphology.