The effect of solvents on the morphology of NTO crystal by molecular dynamics

Abstract

In this paper, a molecular model for adsorption of NTO surface-solvent was constructed, and the effects of different solvents on the morphology of NTO crystal were simulated by molecular dynamics. The selected solvents included ethanol, water, acetone, N-methylpyrrolidone (NMP), ethyl acetate and N,N-dimethylformamide. Pure solvents and two co-solvents including NMP/water and ethanol/water were studied to provide theoretical guidance for the selection of solvent systems for NTO recrystallization. In pure solvents, the results show that the crystal morphology of NTO can be effected by all solvent and in NMP solvent is the best. In co-solvents, when the mass ratio of ethanol to water is 9:1, the best morphology of NTO crystals is found . In ethanol/water system, the morphology of NTO crystals changes from near-cube to cuboid with the decrease of ethanol mass fraction, and the aspect ratios of NTO crystals increase. In NMP/water system, the decrease of the mass fraction of NMP makes the crystal morphology deteriorate. This is manifested as the crystal develops towards a narrow needle shape, and the value of the aspect ratio increases.

Morphology Prediction Methods and Their Applications in Energetic Crystals

“…In recent years, the application of morphology prediction models, such as the MAE models, ,− growth mechanistic model, , and dynamic Monte Carlo simulation method, has become increasing popular. Morphology prediction models have been also widely applied in energetic crystals grown under various conditions, such as vacuum, solvents, and additives, with effects of temperature, volume ratio of mixed solvents, supersaturation, and other conditions covered. − Also, this research revealed the growth mechanism of energetic crystals at the microscopic level, which presented theoretical guidance for morphology control. Meanwhile, valid force fields are important for the specified energetic compounds.…”

Crystal Morphology Prediction Models and Regulating Methods

“…The thickness of the growth slice in a vacuum is definite, while in a solution, the thickness of the solvent layer in the crystal-solvent interface is uncertain. Since the influence of the adsorption of solvent molecules at the crystal face on crystal growth is not considered in the AE model, the attachment energy is usually modified (E mod ), and the modified attachment energy (MAE) model is derived as Equation ( 6) [31][32][33].…”