Strong Ion-solvent Interactions Research Articles

Improving the reliability of classical molecular dynamics simulations in battery electrolyte design

Explorations into new electrolytes have highlighted the critical impact of solvation structure on battery performance. Classical molecular dynamics (CMD) using semi-empirical force fields has become an essential tool for simulating solvation structures. However, mainstream force fields often lack accuracy in describing strong ion-solvent interactions, causing disparities between CMD simulations and experimental observations. Although some empirical methods have been employed in some of the studies to address this issue, their effectiveness has been limited. Our CMD research, supported by quantum chemical calculations and experimental data, reveals that the solvation structure is influenced not only by the charge model but also by the polarization description. Previous empirical approaches that focused solely on adjusting ion-solvent interaction strengths overlooked the importance of polarization effects. Building on this insight, we propose integrating the Drude polarization model into mainstream force fields and verify its feasibility in carbonate, ether, and nitrile electrolytes. Our experimental results demonstrate that this approach significantly enhances the accuracy of CMD-simulated solvation structures. This work is expected to provide a more reliable CMD method for electrolyte design, shielding researchers from the pitfalls of erroneous simulation outcomes.

Studies on the interference of citrate salts on the ion–solvent interactions of ionic liquid with water at different temperatures through volumetric, viscometric, and acoustic methods

The density, viscosity, and ultrasonic velocity of solutions of imidazolium-based ionic liquid, 1-ethyl-3-methyl imidazolium ethyl sulphate ([EMIm][EtSO4]) with aqueous solutions of sodium and potassium salts of citrate have been measured at five different temperatures i.e., T = (298.15–318.15) K and 0.1 MPa pressure. The experimentally found density (ρ) data have been utilized to compute the different volumetric properties such as apparent molar volume (Vϕ), partial molar volume (Vϕ0), partial molar expansivity (Eϕ0), Hepler’s constant (∂Eϕ0/∂T)p and volume transfer (ΔtrVϕ0). Similarly, the Jones-Dole equation, viscosity B-coefficient, transfer properties of B-Coefficient, (ΔtrB) and thermodynamics of viscous flow were calculated from viscosity consequences. The compression properties such as apparent molar isentropic compressibility (Kϕ,S), partial molar compressibility (Kϕ,S0) and transfer partial molar compressibility (ΔtrKϕ,S0) of IL have been deduced from the ultrasonic velocity. All the derived properties have been used to investigate the impact of citrate salts on the ion–solvent interactions of [EMIm][EtSO4] with water. The positive value of each of Hepler’s constants, and ΔtrKϕ,S0 and the negative sign of (dB/dT) indicates the existence of strong ion–solvent interactions and the cosmotrope nature of [EMIm][EtSO4] in the studied systems at the studied temperature ranges. The ion–solvent interactions of the present IL are found to be more in the solutions of potassium citrate (K3Cit) than sodium citrate (Na3Cit).

Insights into the volumetric properties, conductive property, and interaction behaviors of two nitrile functionalized ionic liquids mixture systems with γ-butyrolactone

Two functionalized ionic liquids, 1-cyanopropyl-3-methylimidazolium bistrifluoromethanesulfonimide ([C3CNmim][TFSI]) and 1-cyanopropyl-3-methylimidazolium trifluoromethanesulfonate ([C3CNmim][OTF]) were blended with γ-butyrolactone (GBL) under the full concentration range (molar fraction from 0 to 1) to form mixture systems, respectively. The densities and conductivities of pure ILs and their mixture systems were measured in the temperature range 288.15–343.15 K under normal pressure. The Vogel–Fulcher–Tammann (VFT) equation is employed to investigate the temperature dependence of conductivity. The volumetric properties of the mixture systems, excess molar volumes (VE) and apparent molar volumes (Vϕ), were calculated from the density data. The Redlich–Kister (R–K) polynomial equation and Redlich–Rosenfeld–Meyer (RRM) equation were used for the fittings of the VE and Vϕ, respectively. Further, the behaviors of intermolecular interactions in the mixture systems were explained by a combined analysis method composing of the assessment of the volumetric properties changes, the differential scanning calorimetry (DSC) analysis, the infrared (IR) spectrum shifts, and COSMO-RS methodology based on density functional theory (DFT) calculations. The stable optimized structures, H-bonding information, interaction energies, and charge distributions were consequently obtained. It can be found that the addition of the GBL weakened the hydrogen bonding interactions between the IL cations and anions. The [C3CNmim][TFSI] + GBL mixture system shows the lowest energy difference and it may give strong ion-solvent interactions when compare to [C3CNmim][OTF] mixture system.

Mutual Comparison Studies of Mono and Di Cations in Binary and Ternary Aqueous Electrolytes Solution at 298.15 K

Densities and viscosities of binary and ternary electrolytes solution have been determined experimentally at 298.15 K. The results obtained from density and viscosity measurement have been used to calculate apparent molar volume φv partial molar volume φov at infinite dilution, relative viscosities hrel, A and B coefficients, and free energies of activation of viscous flow of solvent Δ µ10# and solute Δ µ20. The results are discussed in terms of the dehydration effect of the weak ion-ion and strong ion-solvent interactions. The properties of these systems are discussed in terms of the charge, size, and hydrogen bonding effect.

Study of Viscous Behavior for Amino Acid L- Glutamine Aqueous N,N Dimethyl Formamide Solution at Different Temperatures

The densities () and kinematic viscosities (ν) which was converted to the absolute viscosity () from the product of the kinematic viscosity and the density of L-Glutamine have been measured at different temperatures 298.15, 303.15 and 313.15K in aqueous 20% (w/w) dimethyl formamide (DMF) under atmospheric pressure. The value of apparent molar volume (v), limiting apparent molar volume (v ) and viscosity data have been analyzed by using Jones-Dole equation, the Jones-Dole coefficients (A and B) were calculated and excess Gibbs free energy of activation of viscous flow (〖〗^) has been obtained to throw light on the mechanism of viscous flow. The results were interpreted strong ion-solvent interactions in these systems and also structure-maker in 20% DMF + 80% water mixed solvents.

Understanding Nontraditional Differential Mobility Behavior: A Case Study of the Tricarbastannatrane Cation, N(CH2CH2CH2)3Sn.

The effect of strong ion-solvent interactions on the differential mobility behavior of the tricarbastannatrane cation, N(CH2CH2CH2)3Sn+, has been investigated. Exotic "type D" dispersion behavior, which is intermediate to the more common types C and A behavior, is observed for gaseous N2 environments that are seeded with acetone and acetonitrile vapor. Quantum chemical calculations and first-principles modeling show that under low-field conditions [N(CH2CH2CH2)3Sn + solvent]+ complexes containing a single solvent molecule survive the entire separation waveform duty cycle and interact weakly with the chemically modified environment. However, at high separation voltages, the ion-solvent bond dissociates and dynamic clustering ensues.

Volumetric properties of binary mixtures of 1-butyl-3-methylimidazolium halides with water, methanol or ethanol at 293.15 to 318.15 K

Densities of nine binary solutions made of one of three 1-butyl-3-methylimidazolium ([bmim]) halides with water, methanol, or ethanol were measured at atmospheric pressure. The compositions of an ionic liquid ([bmim]Cl, [bmim]Br, or [bmim]I) were increased up to 0.4 as a mole fraction at a given temperature within a range of 293.15 to 318.15 K. The measured values were correlated by a quadratic equation to obtain a temperature dependency of the respective systems. Furthermore, the equation was used to obtain the volume expansivity, which would be used for a pressure-volume-temperature behavior of a condensed phase. The apparent molar volumes were also calculated from the experimental data. The remarkable distinction of the volumetric property behavior between aqueous and nonaqueous solutions was found and attributed to strong ion–solvent interactions in the aqueous systems.

Solvation structure and transport properties of alkali cations in dimethyl sulfoxide under exogenous static electric fields.

A combination of molecular dynamics simulations and pulsed field gradient nuclear magnetic resonance spectroscopy is used to investigate the role of exogenous electric fields on the solvation structure and dynamics of alkali ions in dimethyl sulfoxide (DMSO) and as a function of temperature. Good agreement was obtained, for select alkali ions in the absence of an electric field, between calculated and experimentally determined diffusion coefficients normalized to that of pure DMSO. Our results indicate that temperatures of up to 400 K and external electric fields of up to 1 V nm(-1) have minimal effects on the solvation structure of the smaller alkali cations (Li(+) and Na(+)) due to their relatively strong ion-solvent interactions, whereas the solvation structures of the larger alkali cations (K(+), Rb(+), and Cs(+)) are significantly affected. In addition, although the DMSO exchange dynamics in the first solvation shell differ markedly for the two groups, the drift velocities and mobilities are not significantly affected by the nature of the alkali ion. Overall, although exogenous electric fields induce a drift displacement, their presence does not significantly affect the random diffusive displacement of the alkali ions in DMSO. System temperature is found to have generally a stronger influence on dynamical properties, such as the DMSO exchange dynamics and the ion mobilities, than the presence of electric fields.

Physicochemical properties and ion-solvent interactions in aqueous sodium, ammonium, and lead acetate solution

Densities (ρ), viscosities (η) and refractive indices (nD) of aqueous sodium acetate (SA), ammonium acetate (AA), and lead acetate (LA) solutions have been measured for different concentrations of salts at 302.15 K. Apparent molar volumes (φv) for studied solutions were calculated from density data, and fitted to Masson’s relation and partial molar volume (φvo) was determined. Viscosity data were fitted to Jones-Dole equation and viscosity A- and B-coefficients were determined. Refractive index and density data were fitted to Lorentz and Lorenz equation and specific refraction (RD) were calculated. Behavior of various physicochemical properties indicated presence of strong ion-solvent interactions in present systems and the acetate salts structure maker in water.

Volumetric, rheological, and optical properties of Na-alkylsulfonates aqueous solutions at 29°C

Present paper reports density, relative viscosity and refractive index of sodium salt of 1-heptanesulfonic acid and 1-octanesulfonic acid at 29°C. Density data has been fitted to Masson empirical relation and limiting apparent molar volumes were evaluated. Viscosity A and B coefficients characterizing ion-ion and ion-solvent interactions have been evaluated by fitting viscosity data in Jone-Doles equation. Experimental and calculated properties support the strong ion-solvent interactions in solution.

Effect of Solvents on the Corrosion Inhibition of Copper by 1,2,3-Benzotriazole

Electromotive force (E) measurements have been made at 303.15 K on the cell, CuxHg/CuCl2 (m) in solvent S′ [S′=W or FD or DMF each containing 15 ppm of 1,2,3-benzotriazole (BTA)] /AgCl/Ag (where W, FD and DMF represent the solvents water, formamide and N,N-dimethylformamide, respectively). The Emf data have been compared with the corresponding data under the same conditions in pure W, FD and DMF; the Emf values change from negative to very positive in the presence of BTA in these solutions and suggest the possibility that the presence of BTA in W, FD and DMF helps to bind copper ions with solvent molecules through formation of new complex structures of the film formed on the metal surface. We have suggested the probable mechanism of formation of a protective film through complex formation. The higher Emf values in the presence of BTA indicate strong ion-solvent interactions and the order of interactions was found to be as: FD≥DMF>W. Further iterative procedures were employed to evaluate K1,K2 (dissociation constants), α1,α2 (degrees of dissociation), γ± (mean activity coefficient) and Eo (standard cell potential) making use of the measured E values. The standard molar Gibbs energy of transfer, ΔGtro, of CuCl2 from the pure S to S′ were calculated using the computed standard cell potentials. The calculated ΔGtro values were found to be negative which was indicative of strong ion-solvent interactions and reasonably supported the trend of ion-solvent interactions. From these studies we concluded that BTA acts as a better corrosion inhibitor towards copper in FD and DMF than water.

Ion-Solvent Interactions Investigated by Isentropic Compressibility Measurements of Tetraalkylammonium, Copper(I) and Sodium Salts in Binary Mixtures of Acetonitrile and n-Butyronitrile at 298.15 K

Ultrasonic velocities and densities of binary mixtures of acetonitrile (AN) and n-butyronitrile (n-BTN) with Bu4NBPh4, Bu4 NClO4, Bu4 NI, Bu4NBr, Pr4NBr, Et4NI, Et4NBPh4, NaBPh4, NaClO4 and CuClO4 have been measured in the concentration range 0.0045 - 0.2 mol kg−1 over the entire composition range at 298.15 K. Isentropic compressibilities (Ks) and apparent molal isentropic compressibilities (Ks,ø ) have been calculated. Limiting apparent molal isentropic compressibilities (Ko s,ø ) have been evaluated and split into the contribution of individual ions, i. e. into (Ko s,ø )± values. (Ko s,ø )± for Cu+, Na+ and Br− in all cases is negative and large, for Bu4N+ and Ph4B− positive and large, and for I− and ClO4 − negative only in AN, and becomes positive in binary mixtures of AN and n-BTN for all compositions. The negative (Ko s,ø )± values for Cu+, Na+ and Br− indicate strong ionsolvent interactions involving electrostatic ion-dipole interactions. The large and positive (Ko s,ø )± values for Bu4N+ and Ph4B− show some special type of ion-solvent interactions (hydrophobic or dispersion interactions) with AN and n-BTN. The small negative value changing to a small positive value for I− and ClO4 − indicates the change of a weak electrostatic ion-solvent interaction to another weak special interaction. A comparison of (Ko s,ø )± for Cu+ in some solvent systems shows that the ion-solvent interaction behaviour of Cu+ in AN+ n-BTN is similar to that in AN+ NM, AN+ TEP, BN+ TEP and PY + TEP mixtures but differs from that observed in AN+DMF and AN+DMSO mixtures.

Density and viscosity of magnesium sulphate in formamide + ethylene glycol mixed solvents

Densities (ρ) and viscosities (η) of different strengths of magnesium sulphate (MgSO4) in varying proportions of formamide (FA) + ethylene glycol as mixed solvents were measured at room temperature. The experimental values of ρ and η were used to calculate the values of the apparent molar volume, (φ1,), partial molar volume, (φ1,ℴ) at infinite dilution,A- andB-coefficients of the Jones-Dole equation and free energies of activation of viscous flow, (Δμ 1 0* ) and (Δμ 2 0* ), per mole of solvent and solute respectively. The behaviour of these parameters suggests strong ion-solvent interactions in these systems and also that MgSO4 acts as structure-maker in FA + ethylene glycol mixed solvents.

Electrical conductivity, speeds of sound, and viscosity of aqueous ammonium nitrate solutions

Density, electrical conductivity, speeds of sound, and viscosity of aqueous ammonium nitrate solutions were measured as functions of concentration (m, mol kg–1) (0.1599 [Formula: see text] m [Formula: see text] 20.42) and temperature (T, K) (273.15 [Formula: see text] T [Formula: see text] 323.15). Experimental values are consistent with the reported data. Variation of isotherms of electrical conductivity, isentropic compressibility, and structural relaxation time with concentration evoke structural information on the ion solvation in aqueous ammonium nitrate solution at different concentration regions. The primary hydration numbers of ammonium nitrate were estimated at a particular concentration at which the isentropic compressibility isotherms converge. The existence of free hydrated ions, resulting from strong ion solvent interactions in dilute to 9.1 mol kg–1, the solvent-separated ion-pairs resulting from the relative competition between the ion–solvent and the ion–ion interactions in 9.1 to 12.0 mol kg–1, and the solvent-shared ion-pairs beyond 12.0 mol kg–1 resulting from a decrease in the number of solvent molecules, govern the transport process.Key words: electrical conductivity, speeds of sound, viscosity, ammonium nitrate, hydration number.

A Monte Carlo simulation study of solvent effect on Eu 3+ to Nd 3+ ion mutation

The solvent effects on the relative free energies of solvation of Eu 3+ to Nd 3+ ion mutation have been investigated using a Monte Carlo simulation of statistical perturbation theory. Comparing the relative free energies of Eu 3+ to Nd 3+ ion mutation, in H 2O (TIP4P) in this study with those of the published works, that in H 2O (TIP4P) is −19.11±0.36 kcal/mol in this study, that of the published work in H 2O (TIP3P) is −23.6 kcal/mol and that of experimental work is −19.2 kcal/mol, respectively. There is good agreement among the three studies, considering both methods of obtaining hydration free energies and the standard deviations. For the present Eu 3+ and Nd 3+ ions, the relative free energies of solvation vs. Born's function of bulk solvents decrease with increasing Born's function of bulk solvents except for CH 3OH, THF and MeOMe. The strong ion–solvent interactions in CH 3OH, THF and MeOMe solutions could be due to the electron pair donor properties of the solvents to ion, i.e., Donor number of CH 3OH, THF and MeOMe established by Gutmann. There is also good agreement between the calculated structural properties in this study and the published works obtained by computer simulations and experiments.

A Monte Carlo simulation study of solvent effect on Ca2+ to Mg2+ ion mutation

The solvent effects on the relative free energies of solvation for Ca2+ to Mg2+ ion mutation in several solvents have been investigated by the Monte Carlo simulations of statistical perturbation theory (SPT). We compared the relative free energies for interconversion of Ca2+ to Mg2+ in H2O (TIP3P) in this study with those of the computer simulations and experimental works: that in H2O (TIP3P) is −75.66±1.29kcal/mol in this study and those of the computer simulations in H2O are −75.3, −76.4 and −74.4kcal/mol and that of the experimental work is −74.7kcal/mol, respectively. There is good agreement among several studies if we consider both methods and the standard deviations. For the present Ca2+ and Mg2+ ions, the relative free energies of solvation vs. Born's function of solvents are decreased with increasing Born's function of solvents except for THF and MEOME. The trend of relative free energies of solvation of Ca2+ and Mg2+ ions in THF and MEOME solutions could be explained by the strong ion–solvent interactions existing in THF and MEOME solutions. There is also good agreement between the structural properties in this study and the published works by the ab initio, density function theory (DFT), computer simulation and experimental results.

Solvent effect on Sr 2+ to Ca 2+ ion mutation: Monte Carlo simulation study

We have investigated the solvent effects on the relative free energies of solvation and the difference in partition coefficients of Sr 2+/Ca 2+ mutated to each other in solvents using Monte Carlo simulations with statistical perturbation theory study. Comparing the relative free energies for interconversion of Sr 2+ to Ca 2+, in H 2O (TIP3P), in this study with those of the published works, that of H 2O (TIP3P) is −35.60±0.13 kcal/mol in this study, those of the published works in H 2O are −34.7, −37.5, and −38.8 kcal/mol and that of experimental is −34.9 kcal/mol, respectively. There is a good agreement among the several studies. For the present Sr 2+/Ca 2+ ion pair, the relative free energies of solvation vs. Born’s function of the solvents decreased with increasing Born’s function except for CH 3OH, THF and MEOME. The relative free energies of solvation Sr 2+/Ca 2+ pair in CH 3OH, THF and MEOME could be explained by the strong ion–solvent interactions existing in CH 3OH, THF and MEOME solutions. The strong ion–solvent interactions in CH 3OH, THF and MEOME solutions could be due to the electron pair donor properties of the solvents to ion, i.e., donor number of CH 3OH, THF and MEOME established by Gutmann. There is also a good agreement between the calculated structural properties in this study and the published results obtained by ab initio, computer simulations and experimental works.

A Monte Carlo simulation study of solvent effect on Ba2+ to Sr2+ ion mutation

We have investigated the solvent effects on the relative free energies of solvation for Ba2+ to Sr2+ ion mutation in the solvents using a Monte Carlo simulation of statistical perturbation theory (SPT) study. For the reliability of our computed results, we compared the relative free energies for interconversion of Ba2+ to Sr2+, in H2O (TIP4P) in this study with those of the published works, that in H2O (TIP4P) is −30.24±0.21 kcal mol−1 in this study, those of the published works in H2O are −31.3±3.7, −24.9, and −30.3±0.4 kcal mol−1 and that of experimental work is −30.8 kcal mol−1, respectively. There is good agreement among the several studies, taking into account both methods of obtaining hydration free energies and the standard deviations. For the present Ba2+ and Sr2+ ions, the relative free energies of solvation s. the Onsager dielectric function of bulk solvents decrease with increasing Onsager dielectric function of bulk solvents except for CH3OH, THF and MEOME. The relative free energies of solvation Ba2+ and Sr2+ ions in CH3OH, THF and MEOME could be explained by the strong ion–solvent interactions existing in CH3OH, THF and MEOME solutions. The strong ion–solvent interactions in CH3OH, THF and MEOME could be due to the electron pair donor properties of the solvents to the ion i.e., donor number (DN) of CH3OH, THF and MEOME established by Gutmann (in R. Christian, Solvents and Solvent Effects in Organic Chemistry, VCH, Weinheim, 2nd edn., 1988, p. 20). There is also good agreement between the calculated structural properties in this study and the published works obtained by density functional theory, computer simulations and experiment.

Supercooling phenomena in the binary systems: Acetamide-electrolytes

This paper presents a final discussion on studies of solutions of electrolytes in molten acetamide. These studies deal with cryoscopic and ultrasonic (by shear waves) techniques and reveal the complexity of the behaviour of these systems due to strong ion-solvent interactions.