COMPASS Force Field Research Articles

Molecular dynamics simulation of extraction of Curcuma longa L. extract using subcritical water.

Humans have utilized plants for various purposes, including sustenance and medical treatment for millennia. Researchers have extensively investigated medicinal plants' potential in drug development, spurred by their rich array of chemical compounds. Curcumin, a valuable bioactive compound, is extracted from Turmeric, known by the scientific name Curcuma Longa L. Notably, curcumin boasts potent antioxidant and anti-inflammatory properties, making it a promising candidate for treating cancer and other microbial diseases. Therefore, the simulation study of the extraction of this important medicinal compound by water, which is a green solvent, was carried out. This study employed molecular dynamics simulation for the first time to explore the extraction of Curcuma Longa L. extract using subcritical water. The simulations were carried out at constant pressure and different temperatures, using the Compass force field in the Lammps simulation package. The findings revealed an increase in the amount of Curcuma longa extract with rising temperature, indicating a weakening of hydrogen bonds in water molecules. Water lost its polar state with increasing temperature and became a suitable non-polar solvent for extracting non-polar compounds. The average absolute relative deviation (AARD) for calculated and simulated density data was 6.45%.

Theoretical investigation of potential energetic material CL-20/TNBP co-crystal explosive based on molecular dynamics method.

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/4,4',5,5'-tetranitro-2H,2'H-3,3'-bipyrazole (TNBP)within the molar ratio range of 4:1-1:4 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathways, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, the EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, TNBP, and CL-20/TNBP frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and TNBP particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of the eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 1:1 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 1:1 straddles that of CL-20 and TNBP, representing a new type of insensitive high-energy material. The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/TNBP cocrystals with different ratios and crystal faces. The MD simulation time step is set to 1fs, and the total MD simulation time is 2ns. An isothermal-isobaric (NPT) ensemble is used for the 2ns MD simulation. The COMPASS force field is employed, with the temperature set to 295K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

Theoretical study of potential energetic material CL-20/DNAN eutectic explosive based on molecular dynamics method.

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/2,4-dinitroanisole (DNAN) within the molar ratio range of 9:1-1:9 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathway, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, DNAN, and CL-20/DNAN frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and DNAN particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 4:6 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 4:6 straddles that of CL-20 and DNAN, representing a new type of insensitive high-energy material. The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/DNAN co-crystals with different ratios and crystal faces. The MD simulation time step is set to 1 fs, and the total MD simulation time is 2 ns. An isothermal-isobaric (NPT) ensemble is used for the 2-ns MD simulation. The COMPASS force field is employed, with the temperature set to 295 K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

Molecular dynamics simulation of DNAN/DNB cocrystal PBXs.

The DNAN/DNB eutectic is a high-energy explosive eutectic with superior safety and thermal stability compared to traditional melt-cast explosives. However, the addition of polymer binders can effectively enhance its mechanical properties, allowing for continued production demands without the need for changes to existing factory equipment. In this paper, a model of the DNAN/DNB eutectic explosive was established, and five different types of polymers-cis-1,4-polybutadiene (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), fluorinated polymer (F2603), and polyvinylidene fluoride (PVDF)-were added to the (1 0 - 1), (1 0 1), and (0 1 1) cleavage planes, respectively, to form polymer-bonded explosives (PBXs). The stability, trigger bond length, mechanical properties, and detonation performance of the various polymer-bound PBXs were predicted retrogressively. Among the five PBX models, the DNAN/DNB/PEG model exhibited the highest binding energy and the shortest trigger bond length, indicating a significant improvement in stability, compatibility, and sensitivity compared to the original eutectic. Additionally, although the detonation performance of DNAN/DNB decreased after the addition of binders, the final results were still satisfactory. Overall, the DNAN/DNB/PEG model demonstrated excellent comprehensive performance, proving that among the many polymer binders, PEG is the optimal choice for DNAN/DNB. Within the Materials Studio software, molecular dynamics (MD) simulations were employed to predict the properties of the DNAN/DNB eutectic PBX. The MD simulation timestep was set to 1fs, with a cumulative simulation duration of 2ns. A 2ns MD simulation was conducted using the isothermal-isobaric ensemble (NPT). The COMPASS force field was applied, and the temperature was fixed at 295K.

Molecular dynamics study on the thermal properties of DGEBA/DETA/Ag/SWCNT-Ag composite materials.

Traditional conductive adhesives based on epoxy resin system often encounter problems such as high brittleness and low heat resistance. Therefore, it is particularly important to improve the thermal and mechanical properties of the conductive adhesive. In this study, the effects of SWCNT-Ag and SWCNT fillers on the thermal properties of DGEBA/DETA/Ag conductive adhesive system were studied by using molecular dynamics to construct different cross-linking models. The final results show that the addition of SWCNT and SWCNT-Ag can significantly improve the thermal properties of the conductive adhesive. However, the nanosilver particles on the surface of SWCNT-Ag act as a bridge for the connection between SWCNT and Ag in the conductive adhesive. Therefore, SWCNT-Ag has a more positive impact on the thermal properties of DGEBA/DETA/Ag conductive adhesive system. In this paper, the influence of SWCNT-Ag on the thermal properties of traditional DGEBA/DETA/Ag conductive adhesive system was studied by using Materials Studio software. The volume shrinkage, glass transition temperature, thermal expansion coefficient, and thermal conductivity of the material were calculated based on COMPASS force field. The thermal conductivity is calculated by using reverse non-equilibrium molecular dynamics method. Finally, it is found that SWCNT-Ag has a positive effect on the thermal properties of the conductive adhesive system by comparing several groups of calculation data.

Effect of porosity and temperature on viscosity and diffusivity of benzene liquid containing nanobubble with molecular dynamics

Introduction of nanobubble (NB) into liquid can significantly affect the transport properties such as viscosity and diffusivity, being important in the design and optimization of many liquid-related industrial processes. The present paper reports the atomistic insights into influence of porosity (volume fraction of NBs in solution) and temperature on viscosity and self-diffusion coefficient in benzene liquid containing NBs by using molecular dynamics (MD) simulation with the COMPASS force field. We make molecular modeling of NB-containing benzene liquid using the cubic box with porosities increasing from 0 to 24.6% and conduct a series of MD simulations as increasing temperature from 298 to 343 K. Our simulations reveal that as increasing the porosity the viscosity decreases according to the cubic polynomial while the self-diffusion coefficient increases rapidly. When compared with high polar NB aqueous solutions, although the changing tendencies of transport properties are similar, the changing degrees in benzene liquid are clearly higher, indicating that NB creation has a stronger influence on transport properties of non-polar benzene liquid due to the weaker intermolecular interaction. Meanwhile, as increasing temperature, the viscosity decrease while the self-coefficient increases, both according to the Arrhenius equation. Such temperature dependence is similar to aqueous solution, meaning that temperature affects the transport properties of polar and non-polar liquids alike. This work will contribute to developing NB utilization to practical applications.

Molecular dynamics (MD) study to predict performances of a novel hexanitrohexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI) energetic cocrystal under different temperatures.

To estimate the influence of temperature on properties of 2,4,6,8,10,12-hexanitro- 2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI) cocrystal explosive, the supercell crystal of CL-20/1,4-DNI cocrystal model was established. The mechanical properties, sensitivity, and stability of cocrystal model under different temperatures (T = 225K, 250K, 275K, 300K, 325K, 350K) were predicted. Results show that mechanical parameters, including bulk modulus, tensile modulus and shear modulus are the lowest when temperature is 300K, while Cauchy pressure is the highest, indicating that CL-20/1,4-DNI cocrystal model has better mechanical properties at 300K. Cohesive energy density (CED) and its components energies decrease monotonically with the increase of temperature, illustrating that the CL-20 and 1,4-DNI molecules are activated and the safety of cocrystal explosive is worsened with the increase of temperature. Cocrystal model has relatively higher binding energy when the temperature is 300K, implying that the CL-20/1,4-DNI cocrystal explosive is more stable under this condition. The CL-20/1,4-DNI cocrystal model was optimized and the properties were predicted through molecular dynamics (MD) method. The MD simulation was performed with COMPASS force field and the ensemble was set as NPT, external pressure was set as 0.0001GPa.

Adsorption studies of isoxazole derivatives as corrosion inhibitors for mild steel in 1M HCl solution: DFT studies and molecular dynamics simulation.

The corrosion of mild steel is a significant issue in various industries, prompting the need for effective corrosion inhibitors. This study focuses on understanding the corrosion inhibition properties of organic compounds derived from isoxazole, namely series Iso(a), Iso(b), Iso(c), Iso(d), Iso(e), Iso(f), Iso(g), and Iso(h), which could have implications for materials science and industrial applications. By investigating the influence of different substitutions on these compounds, valuable insights can be gained into designing better corrosion inhibitors for practical use. Theoretical studies were conducted using density functional theory (DFT) with the B3LYP functional and the 6-31G (d,p) basis set. These calculations enabled the evaluation of various parameters including frontier orbital energies (EHOMO, ELUMO), energy gap (∆E), electronegativity (χ), absolute hardness (η), softness (σ), fraction of transferred electrons (∆N), as well as local properties such as natural atomic populations and Fukui indices. Additionally, molecular dynamics simulations were performed to study the adsorption behavior of the inhibitors on the surface of Fe (110). The simulations were conducted using Materials Studio version 8.0 software package using COMPASS force field to understand the impact of different functional groups on the inhibitors before and after adsorption on the iron surface.

Mechanical properties and glass transition temperature of metal-organic framework-filled epoxy resin: A molecular dynamics study

The effect of ZIF-8 (zeolitic imidazolate framework-8) nanoparticles on the mechanical properties of thermoset epoxy-based nanocomposite is investigated using molecular dynamic (MD) simulation. To investigate the effect of the force field type on the results, the mechanical properties and glass transition temperature (Tg) of pure EPON862-TETA polymer were compared at various temperatures using UFF and COMPASS force fields. The results showed that the COMPASS force field provided better simulation results for systems containing polymers. To investigate the effect of ZIF-8 nanoparticle and its size, three simulation boxes were constructed containing cross-linked epoxy resin and ZIF-8 with different sizes while maintaining a weight ratio of 90:10. The mechanical properties and glass transition temperature were calculated for the epoxy/ZIF-8 nanocomposite. The results indicated that adding ZIF-8 nanoparticles improves the Tg, as well as Young's modulus, bulk modulus, and shear modulus at different temperatures compared to the pure epoxy resin.

Measurement and calculation of densities and viscosities of PEC7 and PEC9 using molecular dynamics simulation

To better understand the lubrication characteristics of refrigeration-compressor mechanical moving parts, the thermophysical properties of lubricants in a wide operating range of pressure should be well known, especially viscosity and density. However, the experimental data are always limited, particularly for higher pressures where experiments are difficult to implement. To obtain viscosity and density of lubricants in extreme pressures using a more cost-effective method, the densities and viscosities of pentaerythritol tetraheptanoate (PEC7) and pentaerythritol tetranonanoate (PEC9) were calculated using molecular dynamics (MD) simulations at the temperature range from 263.15 to 343.15 K and pressure range from 0.1 to 1.0 GPa. Compared to the experimental data at low pressures, the maximum relative deviations for density simulations of PEC7 and PEC9 are respectively 0.65 % and 0.70 %. The maximum relative deviations for viscosity simulations of PEC7 and PEC9 are respectively 18.9 % and 5.82 %. MD simulations combined with COMPASS forcefield can successfully calculate the densities and viscosities of pentaerythritol esters.

Analysis of Cerium Ion Transport in Anode Side Catalyst Layer for Improving Polymer Electrolyte Membrane Durability of Polymer Electrolyte Fuel Cells

This study deals with Polymer Electrolyte Fuel Cells (PEFC), which are used in automobiles and household fuel cells. Currently, there are two main challenges for the practical application of PEFCs: durability and cost reduction. The target value for durability is required to be 40,000 hours or more. However, the current durability is about 10,000 hours. Therefore, there is an urgent need to investigate the causes of deterioration and to take countermeasures. One of the causes of degradation is chemical degradation of the polymer electrolyte membrane. When the byproduct hydrogen peroxide encounters impurities such as iron ions, hydroxyl radicals are generated, which attack and degrade the polymer electrolyte membrane. To prevent this degradation, a substance that inactivates hydroxy radicals (radical scavengers) has been featured. Radical scavengers have been added to the polymer electrolyte membranes to prevent this degradation and are now being used in practical applications. One of the most useful radical scavengers is Ce ion. However, it has been observed experimentally that Ce ions in the PEM migrate to the cathode catalyst layer during cell operation. As a result, the Ce ions in the electrolyte membrane are reduced and the electrolyte membrane is degraded by radicals. Conversely, ceria added to the anode microporous layer ionizes and diffuses into the PEM. Because the ceria is ionized, it provides the Ce ions for the electrolyte membrane. However, how Ceion is transported in the catalyst layer and under what conditions it is transported have not been clarified. If Ce ion is not transported sufficiently from the microporous layer to the PEM, it becomes less effective as a radical scavenger and degradation progress. In addition, excessive Ce ion transport also interferes with proton transport in the PEM and reduces the output capacity of the PEFC. However, the cost of running experiments for over 40,000 hours is quite expensive, and the phenomena occurring inside the nanostructured electrolyte membrane are difficult to analyze experimentally. Therefore, simulation analysis is useful to understand the Ce ion transport mechanism in the catalyst layer for controlling Ce ion transport toward improvements of the durability of the electrolyte membrane while maintaining fuel cell performance.In this study, molecular dynamics (MD) simulations have been performed for analysis of structure of Ce ions within ionomers and dynamic properties of Ce ions in catalyst layer. Catalyst layer consists of carbon, polymer chains, Ce ions and solvent molecules, which are water molecules and hydronium ions. A Nafion chain, which has the chemical structure with equivalent weight =1114 was employed. The modified version of the DREIDING force field reported by Mabuchi et al. was used in this study. We have adopted the BOND potential of the COMPASS force field, which is based on the Anharmonic aSPC/Fw Water Model for water molecules and does not consider the Grotthuss mechanism to analyze the effect of cerium ions due to water convection. Water content λ, which indicates the ratio of solvent molecules to sulfonic groups in Nafion, was set at 5, 9 and 13. Twenty polymer chains, 140 hydronium ions and 20 Ce ions were placed in the simulation box with the two-dimensional periodic boundary conditions in the in-plane directions to ensure charge neutrality. The concentration of Ce ions in this case corresponds to 1.1 wt % of the Nafion mass in the membrane. This is a typical concentration for Ce-Nafion composite membranes. We applied to include ionic dipole interaction. For the other molecules, the general 12-6 LJ-type was used, and the arithmetic mixing rule was applied to calculate interaction between them and cerium ions, water oxygen and oxygen of hydronium. The annealing process was applied in order to equilibrate the system. After annealing, the production run was 10 ns using NVE ensemble. The time step was set at 1 fs, and the sampling interval was 5,000 steps. The temperature of the system was set at 323 K, 363 K and 403 K. We will determine where the Ce ions are transported in the catalyst layer by examining the density distribution and diffusion coefficient of Ce ions while changing the initial position of Ce ions. We will also report transport factors by analyzing the structural properties around Ce ions in the presentation. Figure 1

Prediction of water adsorption isotherm on 13X zeolite in different temperatures and investigating the effect of non-framework cations using dynamic simulation

In this article, the adsorption properties of 13X zeolite have been studied using dynamic simulation. The COMPASS force field is used to identify water adsorption isotherm on 13X zeolite. Ewald and Atom-Based group methods were used for the electrostatic and Van der Waals interactions. Li+, Na+, K+, Mg2+and Ca2+ were used as non-framework cations for compensating negative charge. Water adsorption isotherms on the 13X zeolite and different non-framework cations are calculated in the 293.15 – 373.15 K temperature range. Water Adsorption capacity on 13X zeolite for all non-framework cations decreased by increasing the temperature and reducing pressure. Freundlich model was considered for describing water adsorption on 13X zeolite. Isosteric heat of adsorption using the Freundlich model was obtained between the range 44.23 - 83.13 kJ/mol, which has good compliance with the experimental results. The results showed that water has better adsorption on 13X zeolite with Na+ as a non-framework cation compared to the other non-framework cations (Li+, K+, Mg2+and Ca2+), and this type of non-framework cation is a suitable candidate for water adsorption.

Effect of incorporation of multi-walled carbon nanotubes on the CO2/CH4 separation performance of sulfonated poly (ether ether ketone) / polyetherimide composite membranes using design of experiments and molecular dynamics simulation methods

Blend membranes were prepared based on sulfonated poly (ether ether ketone) (SPEEK) and poly (etherimide) (PEI) using different amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 wt%). PEEK has been sulfonated directly to reach 70 % degree of sulfonation. The manufactured membranes were examined by X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). The effect of the composition of SPEEK / PEI on membrane selectivity was investigated under different feed pressures (2 to 8 bar) and temperatures (25 to 55 °C). The values of selectivity and gas permeability were varied between the value of the individual polymers, fluctuating systematically with SPEEK / PEI content variation in the blends. TGA and tensile tests result obtained for prepared membranes shown that the hybrid membrane had good thermal and mechanical properties. The addition of MWCNTs to the blend led to simultaneously improve the selectivity and permeability of the pair gases of CO2 and CH4. The permeability of CO2, as well as CH4/CO2 selectivity for the membrane with the same weight of SPEEK and PEI, and 1 wt% of MWCNTs (coded SP55M1) experienced an increase of about 22 % compared with the neat membrane. Molecular dynamics simulations (MDS) were performed by employing the COMPASS force field to estimate the diffusivity of CH4 and CO2 gases through selected membranes. At last, with compared to the obtained experimetal data, the optimized nanocomposite membrane, integrated with MWCNTs was efficient, which makes it promising platform to separate mixed gase flows of CO2 and CH4 and other related environmental processes.

Effect of intercalated and exfoliated graphite particles on the mechanical properties of polymer composite: A micromechanics-computational approach

This study investigated the effects of intercalation and exfoliation of the graphite flake particles on the mechanical properties of elastomeric composites using analytical, computational, and experimental techniques. Relying on the modified Eshelby and incremental Mori–Tanaka approach, a new micromechanics model was proposed to estimate Young’s modulus and develop a constitutive model for expanded graphite (EG)-filled elastomer in finite strain deformation. It was found that when the initial graphite flakes expanded, the actual volume fraction and ultimate aspect ratio of the dispersed particles significantly affected the mechanical properties of the EG-reinforced composites. The present model and subsequent predictions reflect the initial flake diameter, actual volume fraction, ultimate aspect ratio of the particles, and other convenient physical properties of the composite constituents. In addition, molecular dynamics simulations were performed to evaluate the elastic properties of the EG-Matrix interphase region using the COMPASS force field function. The MD results showed that Young’s modulus of the interphase region increased significantly as the quantity of the graphene layer increased. The micromechanics-constitutive model results were validated using the experimentally determined stress–strain relation of the composites. EG- and CB-elastomer nanocomposite specimens were fabricated and tested in the experimental program. Field emission scanning electron microscopy (FESEM) analysis of the cryo-fractured surfaces of the elastomer compounds showed good interactions between the constituents. Numerical computations indicated that the proposed model incorporating the new parameters could accurately predict the experiment at a small particle concentration.

Effects of MWCNTs on O2/N2 separation performance and morphology of sPEEK/PEI composite membranes: Experimental and molecular dynamics simulation studies

This study involved the development of blend membranes using sulfonated poly (ether ether ketone) (sPEEK) and poly (etherimide) (PEI) with varying amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 % by weight). The gas separation performance of these membranes was evaluated for the separation of O2 and N2 gases. In order to achieve a degree of sulfonation of 70 %, PEEK was sulfonated directly. The manufactured membranes were characterized using X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). Their operational evaluation was performed through permeability tests for pure gases of O2 and N2. The effect of sPEEK/PEI composition on membrane selectivity and gas permeability in the blend was studied. The selectivity and gas permeability values varied between those of individual polymers, fluctuating systematically with sPEEK/PEI content variation in the blends. The addition of MWCNTs to the blend improved the selectivity and permeability of O2 and N2 simultaneously. To further investigate the potential industrial application and stability of these membranes, experiments were conducted under different feed pressures (2 to 8 bar). The membrane containing 1 % of MWCNTs showed the best performance for O2 gas. Molecular dynamics simulations (MDS) were performed using the COMPASS force field to estimate the diffusivity of O2 and N2 gases through selected membrane systems. The simulated results agreed well with the available experimental data. With compared to the reported separating data, the prepared nanocomposite membrane was greatly efficient, which makes it promising platform to separate mixed gas flows and other related environmental processes.

Characterization of Viscoelastic Properties of EPDM Molding Compound for Door Grommet Component Using Molecular Dynamics and Phenomenological Modeling

Abstract The automotive industry is evolving by incorporating innovative tools to improve production processes. A proper manufacturing process influences the behavior of the door grommet during its lifetime. In this paper, molecular dynamics simulations are conducted to evaluate the chemical and physical crosslinking of the EPDM rubber over a range of temperatures using a COMPASS force field. Then, once the ethylene propylene diene monomer (EPDM) model was equilibrated and all possible crosslinks were formed, additional simulations were performed on the model to explore its mechanical behavior. Subsequently, using the superposition principle, viscosity and curing kinetics were evaluated using phenomenological models. To validate the results of the simulations, three injection tests of the door grommet were performed at different temperature conditions. The results indicate that the viscosity and elastic properties increase with increasing levels of crosslink density and that the critical gel point decreases with temperature. Molecular dynamics superposition results in phenomenological models are in reasonable agreement with the kinetic and viscoelastic behavior of EPDM during and after the injection process. The results presented in this paper provide novel molecular-level findings on the crosslinking mechanisms of amorphous polymers and their influence on viscoelastic behavior, which could facilitate the design of the injection process for door grommet applications.

Prediction of Water‐Methanol Mixture Properties by Molecular Dynamics Simulation

Prediction of Water‐Methanol Mixture Properties by Molecular Dynamics Simulation

Effect of temperature on curcumin solubility in a pressurized hot water solvent: Experimental and molecular dynamics simulation

Curcumin is a valuable bioactive compound and has attracted the attention of many researchers due to its wide range of medicinal effects. In this paper, curcumin solubility in pressurized hot water (PHW) was determined by static method, and for the first time, molecular dynamics simulation of curcumin solubility in PHW was performed. Molecular dynamics simulation is a powerful method to predict the atomic behavior of different structures. Here, the simulations were performed using the COMPASS force field and Velocity Verlet motion algorithm in the Lammps simulation package. The simulation results were compared with the experimental results. The results showed that the solubility of curcumin in PHW increases with increasing temperature and the solubility at 418.15 K was >230 times its solubility at ambient temperature. Also, the diffusion coefficients of curcumin increased with increasing temperature, and it was found that the tendency of water molecules to surround the curcumin molecule, which occurs through O(OH curcumin)-H(water) interaction, increased with increasing temperature. The Absolute Average Relative Deviation (AARD) between the experimental and simulated results for solubility and density data was 9.07% and 7.85%, respectively. As a result, the molecular dynamics simulation method well predicted the solubility behavior of curcumin in PHW.

Molecular dynamics simulation of CL20/DNDAP cocrystal-based PBXs.

CL-20/DNDAP cocrystal is a promising new type of explosive with exceptional energy density and detonation parameters. However, compared to TATB, FOX-7 and other insensitive explosives, it still has higher sensitivity. In order to decrease the sensitivity of CL20/DNDAP cocrystal explosive, in this article, a CL20/DNDAP cocrystal model was established, and six different types of polymers, including butadiene rubber (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), hydroxyl-terminated polybutadiene (HTPB), fluoropolymer (F2603), and polyvinylidene difluoride (PVDF), were added to the three cleaved surfaces of (1 0 0), (0 1 0) and (0 0 1) to obtain polymer-bonded explosives (PBXs). Predict the effects of different polymers on the stability, trigger bond length, mechanical properties, and detonation performance of PBXs. Among the six PBX models, CL-20/DNDAP/PEG model exhibited the highest binding energy and the lowest trigger bond length, indicating that CL-20/DNDAP/PEG model had the best stability, compatibility, and the least sensitivity. Furthermore, although the CL-20/DNDAP/F2603 model demonstrated superior detonation capabilities, it should be noted that this model displayed low levels of compatibility. Overall, CL-20/DNDAP/PEG model exhibited the superior comprehensive properties, thereby demonstrating that PEG is a more suitable binder option for PBXs based on the CL20/DNDAP cocrystal. The properties of CL-20/DNDAP cocrystal-based PBXs were predicted by molecular dynamics (MD) method under Materials Studio software. The MD simulation time step was set at 1fs and the total MD simulation time was 2ns. The Isothermal-isobaric (NPT) ensemble was used for the 2ns of MD simulation. The COMPASS force field was used, and the temperature was set at 295K.

Microstructure and mechanical properties of BT/PVTC composite ferroelectric thin films.

Ferroelectric ceramic polymer composites have become the preferred electrocaloric materials due to their light weight and high polarization strength. But the mechanical properties were desired to be improved. In this study, the polyvinylidene fluoride trifluoro ethylene chloride (PVTC) and barium titanate (BT) composites were prepared, and the microstructure and mechanical properties were investigated by molecular dynamics simulations and experiments. It was found that with the increase of BT ceramic content in the composites, the yield stress is significantly reduced, which can be reduced by 16.07%. By comparing with the experimental data, the agglomeration and stress mechanism of the composites were proposed. The microstructure of the composite was analyzed using radial distribution function, self-diffusion coefficient, and glass transition temperature. The agglomeration mechanism of the composite was revealed from the microscopic point of view, and the rationality of the agglomeration behavior was verified by experiments. The calculations were performed by Material Studio 2019 software and the COMPASS force field was adopted.