Crystal Morphology Prediction of 2,6-Diamino-3,5-Dinitropyrazine-1-Oxide (LLM-105) Using a Spiral Growth Model and a Refined OPLS-AA Force Field

Abstract

Diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is representative of low-sensitivity and high-energy compounds with a potential for wide application, and morphology control is crucial to guarantee the application. However, due to insufficient accuracy of general force fields and no kinetic factor considered in common models, it can hardly make accurate morphology predictions, and thus, the control is uncontrollable. This work refines an OPLS-AA force field esspecially for LLM-105 and applies it to morphology prediction with a spiral growth model in three solvents of dimethyl sulfoxide, N-methyl pyrrolidone, and dimethylformamide. By comparing aspect ratios and predominant face areas of the predictions and experiments, we confirm the advantage of our method over other models and force fields. Intermolecular interaction analyses show the dominance of π−π stacking, followed by hydrogen bonding. Due to the strong molecular bond chains dominated by π−π stacking along the [100] edge of the (011) crystal surface, the rod-like growth occurs thereon in all three solvents. This work is rooted in the morphology control of LLM-105 and can also be referred to for other organic molecular crystals.