Insight to the Growth Characteristics and Crystal Morphology of α‐Hemihydrate Gypsum in Na 2 SO 4 Solution

Crystal morphology prediction of 1,3,3-trinitroazetidine in ethanol solvent by molecular dynamics simulation

The attachment energy (AE) model was employed to investigate the growth morphology of Li2CO3 under vacuum and water solvent conditions by molecular dynamics simulations. The attachment energy calculation predicted the growth morphology in vacuum dominated by the (1 1 −1), (0 0 2) and (1 1 0) crystal faces. A modified attachment energy model, accounting for the surface chemistry and the corresponding topography of the habit crystal plane, was established to predict the morphological importance of crystal faces in a water solvent. Moreover, radial distribution function (RDF) and diffusion coefficient analyses were performed to explore the adsorption and diffusion behaviors of solvent molecules on the Li2CO3 crystal faces. The calculated results showed that with the solvent effects, the (0 0 2) and (1 1 0) faces were of great morphological importance, while the (1 1 −1) face disappeared gradually. These finally resulted in a cuboid-like Li2CO3 crystal. The growth morphology and the corresponding X-ray powder diffraction pattern derived from the modified AE model were in accordance with the results observed in experiments. The related model provides an important basis for the further investigation of the effects of impurities.

Molecular modeling of crystal morphology of ginsenoside compound K solvates and its crystal habit modification by solvent molecules

This study describes the molecular dynamics (MD) simulations to investigate the effects of sulfur atom position on the solubility and aggregation properties of asphaltenes extracted from Zaghli crude oil (East Azerbaijan). Two different asphaltene models were studied, i.e., A1 with sulfur in the aromatic ring and A2 with sulfur in the aliphatic side chain. The radial distribution function (RDF) analysis revealed significant differences in aggregation trends. A1 exhibited rapid aggregation in both solvents used in the experiments, as evidenced by a significant decrease in the radius of gyration from 0.6 to 0.4 Å in octane and from 0.8 to 0.5 Å in xylene. In contrast, A2 showed increased solubility; especially in xylene with a marked increase in the radius of gyration from 0.5 to 2 Å. Furthermore, the energy analysis confirmed these results, i.e., A2 exhibited a higher total energy (451.16 kcal/mol) than A1 (221.28 kcal/mol); indicating a more energetically favorable and less aggregated state of A2. These computational results open up new possibilities for understanding the critical role of the sulfur atom position in the asphaltene structure on its aggregation propensity, which can be used to prevent asphaltene-related problems in the petroleum industry. The work is very useful in the oil industry for enhancing oil production by studying asphaltene solubility and aggregation. MD simulations were performed using the COMPASS force field and Material Studio V.6 2017 software to evaluate the solubility of asphaltenes in octane and xylene solvents. Geometric optimization was carried out to address unstable interactions, with periodic boundary conditions applied. Simulations were conducted in the NVT ensemble at 298 K and 1 atm pressure, using a time step of 1 fs, a Nose thermostat for temperature control, and a Berendsen thermostat for pressure control. RDF analysis was utilized to examine the behavior of two distinct asphaltene models, which differed in the positioning of the sulfur atom, in the solvents. The total energy contributions, including van der Waals and electrostatic interactions, were also analyzed.

Habit prediction of 3,4,5-trinitro-1H-pyrazole in four solvent mediums using a molecular dynamics simulation

Growth and morphology of 1,3,5,7-tetranitro-1,3,5,7-tetraazacy-clooct ane (HMX) crystal

Theoretical study on crystal morphologies of 1,1-diamino-2,2-dinitroethene in solvents: Modified attachment energy model and occupancy model

The influence of solutions on ammonium dinitramide (ADN) crystal morphology was investigated using a combined experimental and molecular dynamics simulation approach. Scanning electron microscopy showed that ADN recrystallized from acetone, propanol, dimethyl sulfoxide (DMSO), and ethanol exhibited a lamellar structure, in contrast to the polyhedron structure obtained with isopropanol/NaF. X-ray diffraction analysis revealed that ADN crystals are mainly composed of six crystal faces (010, 011, 110, 100, 121, 031), and acetone, propanol, DMSO, and ethanol result in crystals in which growth at face (100) dominated. Molecular dynamics simulations indicated that the accessible surfaces and lattice energy (Elatt) vary with the crystal faces. The interaction energy between solutions and crystal faces (Eint) was dependent on both crystal faces and solution components, as was the attachment energy (Eatt). The relative standard deviation Rdev′ of the growth rate of the crystal faces was ordered as follows: acetone (0.117) > propanol (0.098) > DMSO (0.094) > ethanol (0.087) > isopropanol (0.078) > isopropanol/NaF (0.073). A larger Rdev′ resulted in a lamellar structure, while a smaller Rdev′ gave more homogeneous growth rates that resulted in polyhedron crystals.

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.

Attachment energy model was adopted to research the influence of external growth environments on e-HNIW crystal morphology. The morphology of e-HNIW crystal in acetone–cyclohexane binary systems was simulated with cyclohexane mass fraction of 0.05, 0.10, 0.15 and 0.20, respectively. The influences of 0.80 acetone on e-HNIW morphology were studied in the acetone–toluene, acetone–benzene and acetone–dichloromethane binary system. Besides, the effects of the temperature and supersaturation on e-HNIW crystal morphology were also examined in the acetone–cyclohexane system. The simulation results reveal that e-HNIW crystal morphology almost maintains consistent with the increase in cyclohexane ratio. Contrarily, the variations of the anti-solvent, the temperature and the supersaturation affect e-HNIW crystal morphology dramatically. Furthermore, the influence of model dimension on the attachment energy was discussed, and a reasonable model size was obtained. The radial distribution function analysis was performed to explore the adsorption and diffusion behaviours of the solvent molecules on the e-HNIW surfaces. Overall, the simulation results can provide some guidance for the crystallization process of e-HNIW.

Polymer-mediated and ultrasound-assisted crystallization of ropivacaine: Crystal growth and morphology modulation

In this study, the crystal morphology of LiOH·H2O in different solvents was predicated through molecular dynamics (MD) simulation. Modified attachment energy (MAE) model was to predict the crystal morphology by calculating the relative growth rate of LiOH·H2O in H2O, CH3CH2OH, and CH3CH2OH/H2O mixed solvent system. The molecular force between the crystal face and the solvent was also analyzed. The calculated results indicate that the main growth surfaces of LiOH·H2O are (1 1 0), (0 0 1), (1 1 − 1), and (2 0 − 1) faces. The crystal habit of LiOH·H2O in the solvent H2O is bulky with a regular shape and a small aspect ratio. The crystal habit of LiOH·H2O in the solvent CH3CH2OH is rhombus, with the most important growth surface of (1 1 0) and an aspect ratio of 1.978. The mixed solvents of CH3CH2OH/H2O with different mass ratios (1:1, 1:3, 3:1) affect the morphology of LiOH·H2O. With the increase of CH3CH2OH content, the exposed area of (2 0 − 1) face tends to be smaller gradually, while the surface of (1 1 0) face was constantly apparent. The mass ratio of 3:1 results in the disappearance of the (2 0 − 1) face. Calculation results using the radial distribution function (RDF) between the crystal face and the solvent CH3CH2OH or H2O show that the long-range electrostatic force is dominant in the interaction between atoms, and a weak Van Der Waals force emerges.

Abstract-The crystal morphology of orthorhombic lysozyme is predicted using the Bravais-Friedel-Donnay-Harker (BFDH) and the attachment energy (AE) models of molecular simulation software Cerius2 in vacuo. The morphology predicted by two models is approximately consistent. The morphology predicted by AE model is in good agreement with the morphology of crystals grown from solution at pH 6.5. The main crystal faces {011},{101}and{110} are observed in morphology predicted by AE model. By cleaving revealable crystal faces in morphology predicted by AE model, surface chemistry visualization and theoretical analysis based on interaction of in intra-molecules or inter-molecules for the important morphological forms are performed. The result shows that steric hindrance and H-band interaction plays critical role for the plate-like morphology of orthorhombic lysozyme.

Exploring the solvent effect on crystal morphology of naphazoline hydrochloride: Molecular dynamic simulations and experiments

Molecular dynamics simulations were conducted using the attachment energy (AE) model to investigate the growth morphology of lead 2,4,6-trinitrororesorcinate (LTNR, lead styphnate) under vacuum and different solvents. The adsorption energy of LTNR on (001), (110), (011), (020), (111), (200), and (201) crystal planes were calculated. Meanwhile, the crystal morphology in solvents of ethanol, toluene, dichloromethane, acetone, dimethyl sulfoxide (DMSO), and water at 298 K was predicted by calculating the interaction energies between the solvents and crystal planes. The calculated results show that the morphology of LTNR crystals in different solvents is significantly different. In toluene, LTNR crystal morphologies are flat, while in pure solvents of ethanol, acetone, and DMSO, the number of crystal planes increases, and the crystal thickness is larger. In the water, LTNR tends to form tabular crystals, which is similar to the experimental results. Both radial distribution function (RDF) and mean squared displacement (MSD) analyses reveal that hydrogen bonding dominates the interactions between LTNR and solvent molecules. Solvent molecules with higher diffusion coefficients exhibit increased desorption tendencies from crystal surfaces, which may reduce their inhibitory effects on specific crystallographic planes. However, no direct correlation exists between solvent diffusion coefficients and crystal plane growth rates, suggesting that surface attachment kinetics or interfacial energy barriers play a more critical role in crystal growth.