Classical molecular dynamics (MD) simulations and quantum chemical density functional theory (DFT) calculations have been employed in the present study to investigate the solvation of lithium cations ...in pure organic carbonate solvents (ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC)) and their binary (EC–DMC, 1:1 molar composition) and ternary (EC-DMC-PC, 1:1:3 molar composition) mixtures. The results obtained by both methods indicate that the formation of complexes with four solvent molecules around Li+, exhibiting a strong local tetrahedral order, is the most favorable. However, the molecular dynamics simulations have revealed the existence of significant structural heterogeneities, extending up to a length scale which is more than five times the size of the first coordination shell radius. Due to these significant structural fluctuations in the bulk liquid phases, the use of larger size clusters in DFT calculations has been suggested. Contrary to the findings of the DFT calculations on small isolated clusters, the MD simulations have predicted a preference of Li+ to interact with DMC molecules within its first solvation shell and not with the highly polar EC and PC ones, in the binary and ternary mixtures. This behavior has been attributed to the local tetrahedral packing of the solvent molecules in the first solvation shell of Li+, which causes a cancellation of the individual molecular dipole vectors, and this effect seems to be more important in the cases where molecules of the same type are present. Due to these cancellation effects, the total dipole in the first solvation shell of Li+ increases when the local mole fraction of DMC is high.
Quantum chemical calculations have been employed to investigate the solvation of lithium cations in ethylene carbonate/propylene carbonate and propylene carbonate/dimethyl carbonate mixed ...electrolytes. The impact of the presence of the counteranion on the solvation of Li+ in pure propylene carbonate and dimethyl carbonate was also studied. The calculations revealed small free-energy changes for the transitions between different preferred structures in mixed solvents. This implies that transitions between distinct local arrangements can take place in the mixtures. The addition of dimethyl carbonate causes a significant increase of the dipole moment of solvation clusters, indicating important molecular-scale modifications when dimethyl carbonate is used as a co-solvent. The presence of an anion in the solvation shell of Li+ modifies the intermolecular structure comprising four carbonate molecules in dilute solutions, allowing only two carbonate molecules to coordinate to Li+. The bidentate complexation of Li+ with the anion’s electron donor atoms, however, maintains the local tetrahedral structure on interatomic length scales. The neutralization of the solvation shell of Li+ due to contact ion pair formation and the consequent implications on the underlying mechanisms provide a rational explanation for the ionic conductivity drop of electrolyte solutions at high salt concentrations.
Understanding the atomic-scale structure of wood microfibrils is essential for establishing fundamental properties in various wood-based research aspects, including moisture impact, wood ...modification, and pretreatment. In this study, we employed molecular dynamics simulations to investigate the arrangement of wood polymers, including cellulose, hemicellulose, and lignin, with a primary focus on the composition of softwood, specifically Norway Spruce wood. We assessed the accuracy of our molecular dynamics model by comparing it with available experimental data, such as density, Young’s modulus, and glass transition temperature, which ensures the reliability of our approach. A key aspect of our study involved modeling the active sorption site for water interaction with wood polymers. Our findings revealed that the interaction between water and hemicellulose, particularly within the hemicellulose–cellulose interphase, was the most prominent binding site. This observation aligns with prior research in this field, further strengthening the validity of our results.
Rechargeable lithium ion batteries are an attractive alternative power source for a wide variety of applications. To optimize their performances, a complete description of the solvation properties of ...the ion in the electrolyte is crucial. A comprehensive understanding at the nanoscale of the solvation structure of lithium ions in nonaqueous carbonate electrolytes is, however, still unclear. We have measured by femtosecond vibrational spectroscopy the orientational correlation time of the CO stretching mode of Li+-bound and Li+-unbound ethylene carbonate molecules, in LiBF4, LiPF6, and LiClO4 ethylene carbonate solutions with different concentrations. Surprisingly, we have found that the coordination number of ethylene carbonate in the first solvation shell of Li+ is only two, in all solutions with concentrations higher than 0.5 M. Density functional theory calculations indicate that the presence of anions in the first coordination shell modifies the generally accepted tetrahedral structure of the complex, allowing only two EC molecules to coordinate to Li+ directly. Our results demonstrate for the first time, to the best of our knowledge, the anion influence on the overall structure of the first solvation shell of the Li+ ion. The formation of such a cation/solvent/anion complex provides a rational explanation for the ionic conductivity drop of lithium/carbonate electrolyte solutions at high concentrations.
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•Different point charges were obtained from DFT calculations for acetic anhydride.•RESP2, AM1-BCC and CM5 charges were fitted.•GAFF and OPLS potentials were applied with fitted ...charges for bulk simulations.•The simulated density and viscosity values were in good agreement with experiments.
Four different charge methods such as RESP2, AM1-BCC, CM1 and CM5 were employed to investigate the properties of acetic anhydride in a bulk phase simulation with GAFF and OPLS force field potentials. These charges were obtained from quantum mechanical calculations by fitting electrostatic potential for RESP2, AM1-BCC and Hirshfeld population for CM5 charges. The calculated density and viscosity values from molecular dynamics simulation were in good agreement with experimental values; however, GAFF with RESP2/AM1-BCC models exhibited higher error (2.1–3.07%) than OPLS with CM1/CM5, which showed the error around 0.1–0.5%.
Owing to its abundant supply from renewable resources, lignin has emerged as a promising functional filler for the development of sustainable composite materials. However, achieving good interfacial ...compatibility between lignin and synthetic polymers, particularly poly (lactic acid) (PLA), remains a fundamental challenge. To advance the development of high-performance bio-based composites incorporating lignin and PLA, our study has scrutinized to unravel the nuances of interfacial binding interactions with the lignin and PLA composite system. Molecular level and experimental examinations were employed to decipher fundamental mechanisms governing and demonstrating the interfacial adhesion. We synthesized casted films of lignin/PLA and acetylated lignin/PLA at varying weight percentages of lignin (5%, 10%, and 20%) and comprehensively investigated their physicochemical and mechanical properties. The inclusion of acetylated lignin in the composites resulted in improved mechanical strength and Young's modulus, while the glass transition temperature and melting point were reduced compared to neat PLA. Systematic variations in these properties revealed distinct compatibility behaviors between unmodified lignin and acetylated lignin when incorporated into PLA. Molecular dynamics (MD) simulation results elucidated that the observed changes in material properties were primarily attributed to the acetylation of lignin. Acetylated lignin exhibited lower Coulombic interaction energy and higher van der Waals forces, indicating a stronger affinity to PLA and a reduced propensity for intermolecular aggregation compared to unmodified lignin. Our findings highlight the critical role of controlling intermolecular interactions and lignin aggregation to develop PLA composites with predictable performance for new applications, such as functional packaging materials.
In this review, we provide a short overview of the Molecular Dynamics (MD) method and how it can be used to model the water splitting process in photoelectrochemical hydrogen production. We cover ...classical non-reactive and reactive MD techniques as well as multiscale extensions combining classical MD with quantum chemical and continuum methods. Selected examples of MD investigations of various aqueous semiconductor interfaces with a special focus on TiO2 are discussed. Finally, we identify gaps in the current state-of-the-art where further developments will be needed for better utilization of MD techniques in the field of water splitting.
Fungal enzymes are effective in degrading various polymeric materials. In this study, we assessed the initial degradation of composites consisting of lignin-poly(lactic acid) (PLA) with both ...unmodified lignin (LIG) and oxypropylated lignin (oLIG) incorporated at 10 % and 40 % weight within the PLA matrix in a fungal environment. Trametes versicolor fungi were used, and the samples were treated only for eight weeks. Although there was no significant difference in weight loss, the degradation process impacted the chemical and thermal properties of the composites, as shown by Fourier transform infrared spectroscopy (FTIR) and Differential scanning calorimetry (DSC) analyses. After the degradation process, the carbonyl index values decreased for all composites and the hydroxyl index values increased for LIG/PLA and a reverse trend was observed for oLIG/PLA composites. The first heating scan from DSC results showed that the melting peak and the cold crystallization peak disappeared after the degradation process. Microscopic analysis revealed that LIG/PLA exhibited higher roughness than oLIG/PLA. Molecular docking simulations were carried out using guaiacylglycerol-β-guaiacyl ether (GGE) and lactic acid (LA) as model compounds for lignin and PLA, respectively, with laccase (Lac) enzyme for Trametes versicolor. The docking results showed that GGE had the strongest binding interaction and affinity with Lac than lactic acid and oxypropylated GGE. The oxypropylated GGE formed a shorter hydrogen bonding with the Lac enzyme than GGE and LA. The trend associated with the degradation of composites from experimental and molecular docking findings was consistent. This combined approach provided insights into the degradation process using fungi and had the potential to be applied to different polymeric composites.
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•The strength of the interaction of binders with graphene is investigated.•The possible orientation of each binder on the graphene surface was evaluated.•Biomass-based binders exhibit ...higher interaction energy than unsustainable binders.•Face-to-face interaction is predominant with each binder case with graphene.
Electrodes are the fundamental components in lithium-ion batteries to develop high-performance device systems. The fabrication process of electrodes involves a mixing of active materials, a nonconductive polymeric binder material, and an electrically conductive additive. Binders play a critical role during the electrochemical process, which tightly holds the active materials together within the electrode to provide a long-cycle life. The present study investigates the strength of the interaction for different binders such as vinylidene fluoride (VDF), pyrrole (PY), styrene-butadiene (SB), acrylonitrile (AN), tetrafluoroethylene (TFE), carboxymethylcellulose (CMC), and lignin monomers, coumarylalcohol (LCmA), coniferylalcohol (LCnA), and sinapylalcohol (LSiA), using density functional theory calculations. The result reveals that sustainable binders (CMC, LCmA, LiCnA, and LSiA) exhibit higher interaction energy than unsustainable binders (VDF, PY, SB, AN, and TFE). The highest interaction energy is obtained for the graphene-LiSiA system, followed by graphene-LCnA and graphene-LCmA. Comparing the orientation of the binders on the graphene surface, all binders make a face-to-face arrangement with graphene. This interaction is greatly enhanced for those binders that possess aromatic rings with functional groups (methoxy and hydroxyl). These results provide significant insights for the use of lignocellulosic biomass materials such as lignin and cellulose as binders in energy devices toward more sustainability.
Refining of industrial lignin to produce homogeneous fractions is essential for high-value applications. However, the understanding of key interactions between a variety of solvents with lignin ...polymer is still uncertain. In this work, single-step fractionation of industrial hardwood kraft lignin (HKL) using organic solvents of different polarities – ethanol, acetone, diethyl ether and hexane – was investigated by combining an experimental and theoretical approach. Experimental results revealed that higher polarity solvents (ethanol and acetone) exhibited higher solubility yield compared to moderate and low polarity solvents. The chemical differences between lignin fractions were proven by pyrolysis gas chromatography mass spectrometry and near infrared spectroscopy. Density functional theory (DFT) results indicated that ethanol presented higher interaction energy followed by acetone, diethyl ether and hexane, which was consistent with experimental findings. Hydrogen bond and non-covalent interaction results from DFT demonstrated that the predominant interaction was found for high polarity of ethanol over other solvents and γ-OH in the lignin model is the key site.
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•Single-step fractionation was carried out for hardwood kraft lignin using 4 solvents.•Higher polarity solvents exhibited higher solubility yield.•Fractionation with diethyl ether leaded to homogeneous low molecular weight fraction.•Quantum chemical calculations showed that ethanol exhibited higher interaction energy.•γ-OH in the lignin model is the key site for strong hydrogen bonding.
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