This paper presents, for ternary lysozyme-Na$_2$SO$_4$-water system, the thermodynamic data extracted from the measured values of four ternary diffusion coefficients and the Onsager reciprocal relations. The calculation for derivatives of solute chemical potentials with respect to solute molar concentrations was made using the method presented in \cite{1}. This method is applicable to systems in which the molar concentration of one solute is very small compared to that of the other, like in our case. The approach is illustrated for the lysozyme chloride-Na$_2$SO$_4$-water system at 25$^o$ C, pH 4.5 and at 0.6 mM (8.6 mg/mL) lysozyme chloride and 0.1, 0.25, 0.5, 0.65, and 0.8 M Na$_2$SO$_4$ concentrations. The calculated solute chemical potential derivatives were used to compute the protein cation charge approximately. We also compute the diffusion Onsager coefficients $(L_{ij})_o$ for each composition at pH 4.5.
We use the conductimetric method, adequate to electrolytes, to determine the lysozyme charge in lys-water and ternary lys-salt-water systems. We measured also the viscosities for the above binary and ternary systems in the same conditions at pH$=4.5$ and T$=298$ K, measurements that allow us to see any effect of viscosity on cations mobilities and implicitly on the lysozyme charge. The method is illustrated for the lysozyme chloride aqueous solution system at 25$^o$ C, using the data reported here for pH$=4.5$ at 0.15, 0.6, 0.8, 1., 1.5, 2., 2.5, 3., 3.5 mM (mg/mL) lysozyme chloride concentrat…
This paper presents a diffusion experimental study for ternary lysozyme-Na$_2$SO$_4$-water system, from moderate precipitant concentrations into the supersaturated region and provides a complete set of four diffusion coefficients. These data are important in order to provide accurate models of protein diffusion with applications in growth of protein crystals for X-ray diffraction studies. All three-component mutual-diffusion experiments reported here were performed by Rayleigh interferometry at pH$=4.5$, T$=25^o$ C and at a mean lysozyme concentration (average of top and bottom solution concen…
This paper presents a combined theoretical and experimental investigation of aqueous near-neutral electrolytes based on chloride salts for rechargeable zinc-air batteries (ZABs). The resilience of near-neutral chloride electrolytes in air could extend ZAB lifetime, but theory-based simulations predict that such electrolytes are vulnerable to other challenges including pH instability and the unwanted precipitation of mixed zinc hydroxide chloride products. In this work, we combine theory-based simulations with experimental methods such as full cell cycling, operando pH measurements, ex-situ XRD…
Inorganic salts are a natural component of biomass which have a significant effect on the product yields from a variety of biomass conversion processes. Understanding their effect on biomass at the microscopic level can help discover their mechanistic role. We present a study of the effect of aqueous sodium chloride (NaCl) on the largest component of biomass, cellulose, focused on the thermodynamic and structural effect of a sodium ion on the cellulose tetramer, and fibril. Replica exchange molecular dynamics simulations of a cellulose tetramer reveal a number of preferred cellulose-Na contact…
The structure of an aqueous solution of sodium chloride at a planar electrode is investigated by integral equation techniques. With the central force water model the aqueous electrolyte is modelled as a mixture of sodium and chloride ions and partially charged hydrogen and oxygen atoms interacting via effective spherically symmetric pair potentials. The bulk correlation functions are obtained from the Ornstein-Zernike equation. With the Wertheim-Lovett-Mou-Buff equation we have calculated the density profiles at the uncharged and charged electrode. Steric interactions between the differently s…
Photoelectron spectroscopy experiments in ionic solutions reveal important electronic structure information, in which the interaction between hydrated ions and water solvent can be inferred. Based on many-body perturbation theory with GW approximation, we theoretically compute the quasiparticle electronic structure of chloride anion solution, which is modeled by path-integral $ab$ $initio$ molecular dynamics simulation by taking account the nuclear quantum effects (NQEs). The electronic levels of hydrated anion as well as water are determined and compared to the recent experimental photoelectr…
Hydrogen bonding to chloride ions has been frequently discussed over the past 5 decades. Still, the possible role of such secondary intermolecular bonding interactions in hydrogen bonded networks has not been investigated in any detail. Here we consider computer models of concentrated aqueous LiCl solutions and compute usual hydrogen bond network characteristics, such as distributions of cluster sizes and of cyclic entities, both for models that take and do not take chloride ions into account. During the analysis of hydrogen bonded rings, a significant amount of 'solvent separated anion pairs'…
Electrochemistry experiments have established that the capacitance of electrode-electrolyte interfaces is much larger for good metals such as gold and platinum than for carbon-based materials. Despite the development of elaborate electrode interaction potentials, to date molecular dynamics simulations were not able to capture this effect. Here we show that changing the width of the Gaussian charge distribution used to represent the atomic charges in gold is an effective way to tune its metallicity. Larger Gaussian widths lead to a capacitance of aqueous solutions (pure water and 1 molar NaCl) …
Highly concentrated aqueous lithium chloride solutions were investigated by classical molecular dynamics (MD) and reverse Monte Carlo (RMC) simulations. At first MD calculations were carried out applying twenty-nine combinations of ion-water interaction models at four salt concentrations. The structural predictions of the different models were compared, the contributions of different structural motifs to the partial pair correlation functions (PPCF) were determined. Particle configurations obtained from MD simulations were further refined using the RMC method to get better agreement with exper…
Aqueous lithium chloride solutions up to very high concentrations were investigated in classical molecular dynamics simulations. Various force fields based on the 12-6 Lennard-Jones model, parametrized for non-polarizable water solvent molecules (SPC/E, TIP4P, TIP4PEw), were inspected. Twenty-nine combinations of ion-water interaction models were examined at four different salt concentrations. Densities, static dielectric constants and self-diffusion coefficients were calculated. Results derived from the different force fields scatter over a wide range of values. Neutron and X-ray weighted str…
A molecular level understanding of the properties of electroactive vanadium species in aqueous solution is crucial for enhancing the performance of vanadium redox flow batteries (RFB). Here, we employ Car-Parrinello molecular dynamics (CPMD) simulations based on density functional theory to investigate the hydration structures, first hydrolysis reaction and diffusion of aqueous V$^{2+}$, V$^{3+}$, VO$^{2+}$, and VO$_2^+$ ions at 300 K. The results indicate that the first hydration shell of both V$^{2+}$ and V$^{3+}$ contains six water molecules, while VO$^{2+}$ is coordinated to five and VO$_2…
We study the solvation free energy of two different conformations (helix and extended) of two different peptides (deca-alanine and deca-glycine) in two different solvents (water and aqueous guanidinium chloride, GdmCl). The free energies are obtained using the quasichemical organization of the potential distribution theorem, an approach that naturally provides the repulsive (solvophobic or cavity) and attractive (solvophilic) contributions to solvation. The solvophilic contribution is further parsed into a chemistry contribution arising from solute interaction with the solvent in the first sol…
In this paper we compare different force fields that are widely used (Gromacs, Charmm-22/x-Plor, Charmm-27, Amber-1999, OPLS-AA) in biophysical simulations containing aqueous NaCl. We show that the uncertainties of the microscopic parameters of, in particular, sodium and, to a lesser extent, chloride translate into large differences in the computed radial-distribution functions. This uncertainty reflects the incomplete experimental knowledge of the structural properties of ionic aqueous solutions at finite molarity.We discuss possible implications on the computation of potential of mean force …
Electrical measurements were performed in dilute aqueous NdCl3 solutions from 298 to 523 K along the 25 MPa isobar to obtain limiting conductances and association constants. The specific conductance data were estimated using a continuous flow cell and a Markov Chain Monte Carlo (MCMC) correction algorithm. The limiting conductances for the salts in water were derived by regressing the mean spherical approximation (MSA) conductance model and speciation analyses based on the MCMC algorithm and the Deep Earth Water (DEW) model. The limiting conductances derived from the experimental data agree we…
Lithium chloride LiCl is widely used as a prototype system to study the strongly dissociated 1-1 electrolyte solution. Here, we combined experimental measurements and classical molecular dynamics simulations to study the ion conduction in this system. Ionic conductivities were reported at both 20$^\circ$C and 50$^\circ$C from experiments and compared to results from molecular dynamics simulations. The main finding of this work is that transference numbers of Li$^+$ and Cl$^-$ become comparable at high concentration. This phenomenon is independent of the force fields employed in the simulation …
We present a new polarizable force field for aqueous ions (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+ and Cl-) derived from condensed phase ab-initio calculations. We use Maximally Localized Wannier Functions together with a generalized force and dipole-matching procedure to determine the whole set of parameters. Experimental data is then used only for validation purposes and a good agreement is obtained for structural, dynamic and thermodynamic properties. The same procedure applied to crystalline phases allows to parametrize the interaction between cations and the chloride anion. Finally, we i…
In spite of a large number of papers published in the last twenty years in the literature, the basic model of liquid water is still controversial. We have measured the dielectric permittivity of pure water and aqueous chlorides solutions in the range 0.2 to 1.5 THz and we have found that the overall dielectric behavior can be satisfactorily described with the weighted average of two single time constant Debye functions. The weights of the two components have been obtained by infrared spectra analysis and are related to two populations of water molecules having a different long range organizati…
Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question bot…
In this work, the solvation and electronic structure of the aqueous chloride ion solution was investigated using Density Functional Theory (DFT) based \textit{ab initio} molecular dynamics (AIMD). From an analysis of radial distribution functions, coordination numbers, and solvation structures, we found that exact exchange ($E_{\rm xx}$) and non-local van der Waals (vdW) interactions effectively \textit{weaken} the interactions between the Cl$^-$ ion and the first solvation shell. With a Cl-O coordination number in excellent agreement with experiment, we found that most configurations generate…
We investigated isolated sodium/chloride aqueous droplets at the microscopic level, which comprise from about 5k to 1M water molecules and whose salt concentrations are 0.2$m$ (brackish water) and 0.6$m$ (sea water), by means of molecular dynamics simulations based on an \emph{ab initio}-based polarizable force field. The size of our largest droplets is at the submicron particle marine aerosol scale. From our simulations, we investigated ion spatial distributions, ion aggregates (size, composition, lifetime and distribution), droplet surface potentials and the densities of the water vapor surr…
Adding salt to water at ambient pressure affects its thermodynamic properties. At low salt concentration, anomalies such as the density maximum are shifted to lower temperature, while at large enough salt concentration they cannot be observed any more. Here we investigate the effect of salt on an anomaly recently observed in pure water at negative pressure: the existence of a sound velocity minimum along isochores. We compare experiments and simulations for an aqueous solution of sodium chloride with molality around $1.2\,\mathrm{mol\,kg^{-1}}$, reaching pressures beyond $-100\,\mathrm{MPa}$. …
Thermodynamic property calculations of mixtures containing carbon dioxide (CO$_2$) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data. In this report, we recommend two different models for enthalpy calculations: the CPA equation of …
Kosmotropic cosolvents added to an aqueous solution promote the aggregation of hydrophobic solute particles, while chaotropic cosolvents act to destabilise such aggregates. We discuss the mechanism for these phenomena within an adapted version of the two-state Muller-Lee-Graziano model for water, which provides a complete description of the ternary water/cosolvent/solute system for small solute particles. This model contains the dominant effect of a kosmotropic substance, which is to enhance the formation of water structure. The consequent preferential exclusion both of cosolvent molecules fro…
