Prediction of crystal morphology of 3,4-Dinitro-1H-pyrazole (DNP) in different solvents

Theoretical study on the influence of different solvents on the growth morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF)

CONTEXT

3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) is a new energetic compound with high energy and high density, and it is an important component of propellant and melt cast explosive. In order to study the effect of solvent on the growth morphology of DNTF, the growth plane of DNTF in vacuum is predicted by attachment energy (AE) model, and then the modified attachment energy of each growth plane in different solvents is calculated by molecular dynamics simulation. The morphology of crystal in solvent is predicted by modified attachment energy (MAE) model. The factors affecting crystal growth in solvent environment are analyzed by mass density distribution, radial distribution function and diffusion coefficient. The results show that the growth morphology of crystal in solvent is not only related to the adsorption strength of solvent to crystal plane, but affected by the attraction of crystal plane to solute. The hydrogen bond plays an important role in the adsorption strength between solvent and crystal plane. The polarity of solvent has a great influence on the crystal morphology, and the interaction between the solvent with stronger polarity and the crystal plane is stronger. The morphology of DNTF in n-butanol solvent is closer to spherical, which can effectively reduce the sensitivity of DNTF.

METHODS

The molecular dynamics simulation is carried out under the COMPASS force field of Materials Studio software. Gaussian software is used to calculate the electrostatic potential of DNTF at B3LYP-D3/6-311 + G (d, p) theoretical level.

Molecular Forcefield Methods for Describing Energetic Molecular Crystals: A Review

Energetic molecular crystals are widely applied for military and civilian purposes, and molecular forcefields (FF) are indispensable for treating the microscopic issues therein. This article reviews the three types of molecular FFs that are applied widely for describing energetic crystals-classic FFs, consistent FFs, and reactive FFs (ReaxFF). The basic principle of each type of FF is briefed and compared, with the application introduced, predicting polymorph, morphology, thermodynamics, vibration spectra, thermal property, mechanics, and reactivity. Finally, the advantages and disadvantages of these FFs are summarized, and some directions of future development are suggested.

Study on the formation mechanism of isoniazid crystal defects and defect elimination strategy based on ultrasound

In crystallization, crystal growth defects may reduce the strength and purity of crystals, which are not welcomed in the industry. Herein, isoniazid (INH) crystals were chosen as an example to investigate the formation of crystal defects at the molecular scale by combining experiments and molecular dynamics simulations. It was found that the strong interaction between the solvent and the crystal surface, high temperature, small stirring rate, and low supersaturation can lead to more pronounced crystal defects. The bulk severity of INH crystal defects was reflected by N₂ adsorption-desorption measurement. Besides, the single-crystal growth experiments manifested the rough growth mechanism for the (110) surface in the axial direction and the stepwise growth mechanism for the (002) surface in the radial direction. For the (110) surface, cavities occurred under the condition where the growth rate of the crystal edges and corners was greater than that of the surface center due to the starvation phenomenon of diffusion. While for the (002) surface, when the solvent removal rate was lower than the solute insertion rate, liquid inclusions were formed, which was verified by Raman microscopy. Furthermore, the ultrasonic strategy was successfully proposed to eliminate INH crystal defects and prepare perfect INH crystals. Moreover, the mechanism of ultrasound to reduce the crystal defect was proposed. We believe this work can provide insights into the design and preparation of defect-free crystals in crystallization.

Effect of modification of binary solvent molecules on ε-CL-20 crystal morphology: a molecular dynamics study

The effects of thirteen binary solvent systems on the growth of CL-20 were studied by molecular dynamics simulation, and the effect of antisolvent properties on the solvent inhibition was systematically investigated.

Structure and Morphology of Indole Analogue Crystals

Indole and six simple analogues were crystallized in different environments to study the crystal habit changes. All crystal structures were determined by X-ray diffraction experiments. Lattice energies based on DFT-D3 periodic calculations and framework analysis were used to define the most important intermolecular interactions in the crystal structures: N-H···π (-28 kJ/mol), hydrogen bonds (-34 kJ/mol), π···π stacking interactions (-18 kJ/mol), and dipole-dipole (-18 kJ/mol). As morphology is an important feature in many industrial applications, such as photovoltaic cells, electronic devices, and drug discovery, we predicted the crystal morphology of selected crystals using the BFDH and AE models. Facet character depends on the orientation of the molecules at the surface and is therefore sensitive to the variation of crystallization conditions such as solvent, method, and temperature. All indole derivatives tend to form plate crystals with the largest {002} facet. We showed that the morphological importance of the {002} facet increases, whereas the {011} facet decreases with solvent polarity for 5-nitroindole and 4-cyanindole crystals, resulting in a change of crystal habit from needle to plate and from plate to prism, respectively.

Solvent Effects on Catechol Crystal Habits and Aspect Ratios: A Combination of Experiments and Molecular Dynamics Simulation Study

This work could help to better understand the solvent effects on crystal habits and aspect ratio changes at the molecular level, which provide some guidance for solvent selection in industrial crystallization processes. With the catechol crystal habits acquired using both experimental and simulation methods in isopropanol, methyl acetate and ethyl acetate, solvent effects on crystal morphology were explored based on the modified attachment energy model. Firstly, morphologically dominant crystal faces were obtained with the predicted crystal habit in vacuum. Then, modified attachment energies were calculated by the molecular dynamics simulation to modify the crystal shapes in a real solvent environment, and the simulation results were in agreement with the experimental ones. Meanwhile, the surface properties such as roughness and the diffusion coefficient were introduced to analyze the solvent adsorption behaviors and the radial distribution function curves were generated to distinguish diverse types of interactions like hydrogen bonds and van der Waals forces. Results show that the catechol crystal habits were affected by the combination of the attachment energy, surface structures and molecular interaction types. Moreover, the changing aspect ratios of catechol crystals are closely related to the existence of hydrogen bonds which contribute to growth inhibition on specific faces.

Molecular Modeling on Morphology of 3,4-Bis(3-nitrofurazan-4-yl)furoxan Crystals in Dichloroethane or Benzene Mixture Solvents

According to the experiments, DNTF crystallizes in benzene/methylbenzene (1:1), benzene/methylbenzene/ethanol (2:3:5), and sym-dichloroethane solvents into two similar crystal shapes, namely strip and tetrahedral. There is a possibility that solvent changes the crystal morphology. In order to explain this phenomenon, the DNTF growth interface model was constructed according to the actual solution environment. The interaction energy between the solvent phase and the DNTF crystal face was studied by means of molecular dynamics simulation. The crystal morphology of DNTF was predicted using the classical modified attachment energy model (MAE) in benzene, methylbenzene, benzene/methylbenzene (1:1), benzene/methylbenzene/ethanol (2:3:5), and sym-dichloroethane. The results show that the DNTF growths are mainly dominated by the (011), (001), (101), (110), (111), and (11[Formula: see text]) faces in vacuum. However, only a few faces will remain in the solvents, of which the (011) and (101) faces are exposed in benzene, methylbenzene, and benzene/methylbenzene (1:1), and only the (111) faces constitute the crystal shape of the DNTF in benzene/methylbenzene/ethanol (2:3:5) and sym-dichloroethane. The predicted results successfully explained the observed phenomena in the experiment. The simulation results can provide some guidance for the crystallization process of DNTF.

Molecular dynamics simulation on the morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) affected by dimethyl sulfoxide (DMSO) and temperature

The attachment energy (AE) model is adopted to research the influence of dimethyl sulfoxide (DMSO) and temperature on the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7). FOX-7 crystal habits in DMSO at different temperatures simulated by the AE model have apparently changed compared with the vacuum morphology, indicating that the solvent and temperature can affect FOX-7 morphology. Moreover, the influence of model dimension on the attachment energy has been studied, and a reasonable model size is obtained based on the model dimension study results. Besides, the radial distribution function analysis shows that the solvent molecules adsorb on the FOX-7 surfaces mainly via the solvent–crystal interface interactions of van der Waals forces (vdW) and Coulomb interactions. The analysis of diffusion coefficient of DMSO molecules on the crystal growth surfaces shows that the growth habit is also influenced by the diffusion capacity of DMSO molecules. These simulation results of this study can provide some guidance for the crystallization process of FOX-7.

Tuning crystallization and stability of the metastable polymorph of dl-methionine by a structurally similar additive

Polymorph formation, transformation and crystal morphology were simultaneously tuned through a tailor-made additive via theoretical simulations combined with experimental methods.

Predicting the crystal habit of photoinitiator XBPO and elucidating the solvent effect on crystal faces

Elaborating the solvent effect on crystal faces using an affinity degree model at the molecular level.

Morphology control of 3-nitro-1,2,4-triazole-5-one (NTO) by molecular dynamics simulation

The vacuum, water-effect and ethanol-effect morphology of 3-nitro-1,2,4-triazole-5-one (NTO) is simulated using the attachment energy model by the molecular dynamics (MD) simulation method.