Improved Force Field Model for the Deep Eutectic Solvent Ethaline: Reliable Physicochemical Properties (original) (raw)
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Frontiers in Chemistry
The addition of molecular liquid cosolvents to choline chloride (ChCl)-based deep eutectic solvents (DESs) is increasingly investigated for reducing the inherently high bulk viscosities of the latter, which represent a major obstacle for potential industrial applications. The molar enthalpy of mixing, often referred to as excess molar enthalpy HE—a property reflecting changes in intermolecular interactions upon mixing—of the well-known ChCl/ethylene glycol (1:2 molar ratio) DES mixed with either water or methanol was recently found to be of opposite sign at 308.15 K: Mixing of the DES with water is strongly exothermic, while methanol mixtures are endothermic over the entire mixture composition range. Knowledge of molecular-level liquid structural changes in the DES following cosolvent addition is expected to be important when selecting such “pseudo-binary” mixtures for specific applications, e.g., solvents. With the aim of understanding the reason for the different behavior of selec...
Journal of Physical Chemistry B, 2020
In recent years molecular dynamic simulations on Choline Chloride based Deep Eutectic Solvents (DES) have flourished. Most of these studies point to the fact that in order to accurately reproduce dynamical properties of the latter using a fixed-charge atomistic Force Fields (FF) one has to resort to charge scaling. In this work, we propose an alternative to charge scaling and show that the sole refinement of the LENNARD-JONES parameters of the oxygen and hydrogen of the hydroxyl function in the GAFF v2.11 FF, enables for an accurate description of static, dynamical and structural properties of two commonly used DES, namely ETHALINE (1:2 mixture of Choline Chloride and Ethylene Glycol) and GLYCELINE (1:2 mixture of Choline Chloride and Glycerol). Various computed physicochemical properties for both mixtures with our modified version of the GAFF v2.11 FF are found in good agreement with experimental data. Most importantly however, is the fact that self-diffusion coefficients for the various components of both ETHALINE and GLYCELINE are found within a maximum deviation of 33% from experimental values, which is at least as good if not better as current scaled-charge FF. Finally, computed radial distribution functions match with those reported in the literature.
2022
In our work, we have studied the formation of choline chloride based NADESs using DFT calculations, and all-atom classical Molecular Dynamics (MD) simulations. In our DFT calculations, the ground state geometry optimizations were performed in the gas phase using DFT B3LYP 6-31+G(d) level of theory. Moreover, all-atom classical Molecular Dynamics simulations were implemented using Gromos force eld. The DFT calculation results revealed the formation of NADESs via formation (creation) of binding between chlorine and choline, and chlorine and glucose. Next, the results of all-atom classical Molecular Dynamics simulations, based on the time average of the equilibrated production run of MD simulations, stated that the nitrogen atom of choline ion, and chloride ion have greater interactions, while chloride ion have also greater interaction with glucose during formation of NADES. Highlights Intermolecular interactions of NADES were studied by DFT calculations and all-atom classical Molecular Dynamics simulations.
Journal of Molecular Liquids, 2021
In the current study, molecular dynamics simulations were conducted to investigate the structural and dynamical properties of glucose-based Deep Eutectic Solvents (DESs) at different molar ratios (the mixture of glucose and choline chloride with the molar ratios of 1:3, 1:1 and 3:1). Accordingly, the interaction energies of different species and structural properties such as atom-atom radial distribution functions (RDFs), the hydrogen-bonding network between species, and spatial distribution functions (SDFs) were computed to understand effective interactions in the eutectic mixture formation. It was found that the insertion of glucose molecules reduced the accumulation of chloride anions around choline cations, eventually decreasing the interaction between the choline chloride ion pairs. Moreover, the possible explanations for the thermos-physical properties of DESs, such as the shear viscosity and density, have been provided. Dynamical properties of DES were evaluated by calculating the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of the mass of the ions and glucose molecules. MSD analysis results were then used to calculate the self-diffusion parameter by applying the Einstein relation. The simulation results indicated that increasing the temperature led to easing the migration of the molecules and decreasing the dependence of the movement of the molecules on each other. This growing trend of migration may lead to an increase in the self-diffusion coefficient of molecules. Structural analysis revealed that a ratio of 1:1 of glucose: choline chloride could provide the best condition to maintain the low melting point of the mixture due to the strong hydrogen-bonded network between the two species.
Evolution of microscopic heterogeneity and dynamics in choline chloride-based deep eutectic solvents
Nature Communications
Deep eutectic solvents (DESs) are an emerging class of non-aqueous solvents that are potentially scalable, easy to prepare and functionalize for many applications ranging from biomass processing to energy storage technologies. Predictive understanding of the fundamental correlations between local structure and macroscopic properties is needed to exploit the large design space and tunability of DESs for specific applications. Here, we employ a range of computational and experimental techniques that span length-scales from molecular to macroscopic and timescales from picoseconds to seconds to study the evolution of structure and dynamics in model DESs, namely Glyceline and Ethaline, starting from the parent compounds. We show that systematic addition of choline chloride leads to microscopic heterogeneities that alter the primary structural relaxation in glycerol and ethylene glycol and result in new dynamic modes that are strongly correlated to the macroscopic properties of the DES fo...
This paper reports the physicochemical (density, dynamic viscosity, electrical conductivity and refractive index) and the thermodynamic (thermal expansion coefficient, molecular volume, lattice energy and heat capacity) properties of several choline chloride (ChCl) based deep eutectic solvents (DESs), with 1:2 mole ratio, respectively: ChCl:propylene glycol, ChCl:1,3-dimethyl-urea and ChCl:thiourea, at atmospheric pressure as a function of temperature over the range of 293.15–363.15 K. Their properties were also compared with those of some already characterized ChCl-based DESs, namely ChCl:ethylene glycol, ChCl:glycerol and ChCl:urea (1:2 mole ratio). Density, viscosity and refractive index of all DESs decrease with the increasing temperature while the electrical conductivity increases. Viscosity and conductivity of the tested DESs were fitted by both Arrhenius-type and Vogel–Tamman–Fulcher equations. The changes of molar enthalpy, entropy and Gibbs energy of activation, determined using the Eyring theory, demonstrated the interactional factor as predominant over the structural factor for all DES systems. The fractional Walden rule, used to correlate molar conductivity and viscosity, showed an excellent linear behaviour. It was shown that ChCl:propylene glycol DES had properties similar to ChCl:ethylene glycol and ChCl:glycerol DESs. However, the properties (density, viscosity and electrical conductivity) of ChCl:1,3-dimethyl-urea and ChCl: :thiourea DESs were inferior to those of the ChCl:urea DES.
Fluid Phase Equilibria, 2019
The three steps systematic parameterization procedure, 3SSPP, to develop force fields of polar liquids proposed by our group (J. Chem. Theory Comput. 2015, 11, 683) is reviewed. The method allows obtaining independently the charge distribution and Lennard-Jones parameters of pure components if the experimental dielectric constant, surface tension and liquid density are used as target properties. Different methods to determine the partial atomic charges from electronic structure calculations of isolated polar molecules are analyzed. It is shown that the charge distribution plays an important role in several properties of pure components and binary mixtures, including solubility. Molecular dynamics simulations of 12 typical polar liquids in aqueous solutions show that the TraPPE-UA force field, in general, underestimates the experimental solubility in a liquid-liquid equilibrium at room conditions. The 3SSPP is used to reparameterize the TraPPE-UA non-bonding parameters of liquid 1-propanol, 2-pentanone and methyl acetate using scaled atomic charges from the Hirshfeld partition scheme. The new parameters predict the correct solubility of 1-propanol in water but fail to reproduce that of the other two molecules. The new parameterization procedure, 4SSPP, is extended to include the solubility as a target property. The solubility is reproduced by modifying the charge distribution obtained for the pure components keeping constant the molecular dipole moment and Lennard-Jones parameters. The method is applied to 2-pentanone and methyl acetate as pure components and their mixtures with water. The target properties of the pure components are almost unaffected after the refining process of the charge distribution. The liquid-vapor phase diagram is also determined for a single component. The results show that the use of an explicit solvent, water in this case, in a simulation is a good way to improve, with a small additional computational cost, the force field parameters of pure components to be used in computer simulations in multicomponent systems. The new parameters are used to obtain the liquid density of 1-propanol/methanol and methyl acetate/methanol mixtures and excellent agreement with experimental data is found.
Journal of Chemical Theory and Computation, 2012
The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys. 2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed expos e of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats, treatment of electrostatic interactions, and system size (1000 molecules). The densities and enthalpy of vaporization from an independent data set based on simulations using the CHARMM General Force Field (CGenFF) presented by Vanommeslaeghe et al. (J. Comput. Chem. 2010, 31, 671) are included for comparison. We find that, overall, the OPLS/AA force field performs somewhat better than GAFF, but there are significant issues with reproduction of the surface tension and dielectric constants for both force fields.