Thermodynamic Properties Of Solutions Research Articles

A Method for Efficiently Predicting the Radial Distribution Function and Osmotic Coefficients of Aqueous Electrolyte Solutions.

The prediction of the structural and thermodynamic properties of electrolyte solutions is critical for a huge range of practical situations where these solutions play a vital role. Theoretical models, such as the continuum solvent model, attempt to explain the behavior of solutions using a coarse-grained description of the interactions of species in the solution, whereas molecular simulations aim to directly compute the behavior of the solution, including the interactions between all ions and molecules in the system. Both methods have limitations: theoretical models are generally less accurate because they rely on assumptions, while molecular simulations require significant computational resources, particularly if higher accuracy is desired. To address these issues, we propose an affordable and effective method that combines the advantages of the modified Poisson-Boltzmann equation (MPBE) with classical molecular dynamics (MD) simulations to predict the radial distribution functions and thermodynamic properties of electrolyte solutions. We demonstrate a method of using the MPBE to compute the short-range potential of mean force (PMF) from the radial distribution functions (RDFs) and vice versa. Furthermore, we provide insights into the relationship between the RDFs and the short-range PMF based on the MPBE. Our analysis reveals that the effective short-range PMFs can be approximately calculated using low concentration simulations but the short-range PMFs are slightly concentration-dependent in simulations at higher concentrations. Additionally, we demonstrate that for concentrated solutions, osmotic coefficients can be calculated in agreement with experiment using a virial approach. This is based on the effective short-range PMFs and RDFs obtained from the MPBE method. Our proposed MPBE can therefore accelerate the calculation of the structural and thermodynamic properties of electrolyte solutions.

A Unified Extrapolation thermodynamic model for multicomponent solutions based on binary data

Predicting the thermodynamic properties of multicomponent solution based on binary data is highly desirable. However, traditional methods face many challenges in practical applications due to the unclear mechanisms for obtaining the molar composition of sub-binary terms. In this article, a new extrapolation model is suggested, which derived from the assumption of the Kohler model. It determines the molar composition points of each sub-binary system through a clear mechanism by introducing the contribution coefficient, defined by the property differences between two components. Moreover, the new model can mathematically obtain all potential molar composition points of sub-binary systems. Additionally, a simple and effective method for calculating the property difference between two components is recommended. The performance of this new extrapolation model is demonstrated in several multicomponent alloy systems with different properties.

Energetic processes and thermodynamic analysis of the spinning Kiselev black hole with cloud of strings

Here we study the impact of the string clouds, the quintessence dark energy and other spacetime parameters on the center-of-mass energy, Penrose-process and thermodynamic properties of a stationary black hole solution of the Einstein field equations. We observe that the three distinct horizons i.e the Cauchy horizon, the event horizon and the cosmological horizon exist when the spin parameter a of the black hole is less than its extremal value aE. Interestingly we see that the infinite redshift surface of the black hole is not much sensitive to the quintessence parameter γ. It is sensitive to the parameter a and it increases as the parameter a increases. Further, we notice that an increase in the string cloud parameters b, quintessence parameter γ and a make the radius of the ergosphere of the black hole larger. We also notice that a rise in the parameter a makes the innermost stable circular orbits (ISCO) smaller and for an increase in the parameter b and γ the ISCO becomes larger than that for the Kerr spacetime. For the center-of-mass energy of the spinning black hole with quintessence and cloud of strings we observe that it can be arbitrarily high only for the extremal case of the black hole for a specific range of values of the angular momentum of the colliding particles. We notice that the Penrose-process is more efficient for smaller values of the string cloud parameter b and the parameter γ has no significant impact on this process. Moreover we see that an increase in the parameters b, γ and a cause the Helmholtz free energy to increase and opposite is true for the temperature of this type of rotating black hole. We learn that the area and entropy of the black hole are also depend on the parameters b, γ and a, and their effect make the entropy smaller. Interestingly we find a range of the horizon radius for the thermodynamic stability of the black hole. To get more information about the thermodynamic quantities of the rotating black hole with quintessence and cloud of strings, we plot them for different ranges of the spacetime parameters.

Experimental research of a novel binary solution for diffusion absorption cooling systems

AbstractThe diffusion absorption refrigeration (DAR) systems are driven by heat and utilize a binary solution along with an inert gas as the working fluid. In commercial applications, the choice of binary solutions operating with an auxiliary gas is typically limited to ammonia‐water or water‐lithium bromide combinations. The focus of this study is to explore the viability of using tetrafluoropropene (R‐1234yf, an HFO refrigerant) as the refrigerant, dimethylacetamide (DMAC) as the absorbent, and helium as the auxiliary gas. As the thermodynamic properties of this specific binary solution are yet to be studied, experimental investigations are conducted to obtain these properties. The results allow the establishment of the pressure‐temperature and concentration relationships and determine the mixture‘s enthalpy for various temperatures. Subsequently, both numerical and experimental analyses of the diffusion absorption system are performed. The experimental findings show that, under certain concentrations of the components and with appropriate heat input, temperatures in the evaporator reached below 0 °C. However, the system exhibits low coefficient of performance values, high generation temperatures, and overall inefficiency, suggesting that this particular binary solution may not be well‐suited for diffusion absorption cooling systems.

Insight into the solution thermodynamic properties of cimetidine form A and form B based on experiments and molecular simulations

Cimetidine (CIM) is an antagonist of the type II histamine receptors, and act as a significant agent in the treatment of stomach ulcers. In this work, the effect of polymorphism and solvent type on the thermodynamic properties of CIM was investigated based on experimental results and molecular simulations. The solubility data of two polymorphs for CIM (forms A and B) in organic solvents were measured and correlated with four thermodynamic models. It could be found that the solubility of CIM form A is higher compared to form B. In addition, molecular simulations were adopted to investigate the mechanism of the solubility and stability of the two forms. Hirshfeld surface analysis shows that strong H···N interaction contributes to better stability of form B. Meanwhile, molecular electrostatic potential surface and radial distribution function results indicate that the solubility behavior is significantly influenced by the intensity of the solute–solvent interactions. Finally, the dissolution thermodynamic properties, including the enthalpy change, the Gibbs energy change, and the entropy change, were calculated and the results show that the dissolution process of CIM is endothermic, entropy-driven and spontaneous.

Theoretical and practical investigation of ion-ion association in electrolyte solutions.

In this study, we present a new equation of state for electrolyte solutions, integrating the statistical associating fluid theory for variable range interactions utilizing the generic Mie form and binding Debye-Hückel theories. This equation of state underscores the pivotal role of ion-ion association in determining the properties of electrolyte solutions. We propose a unified framework that simultaneously examines the thermodynamic properties of electrolyte solutions and their electrical conductivity, given the profound impact of ion pairing on this transport property. Using this equation of state, we predict the liquid density, mean ionic activity coefficient, and osmotic coefficient for binary NaCl, Na2SO4, and MgSO4 aqueous solutions at 298.15K. Additionally, we evaluate the molar conductivity of these systems by considering the fraction of free ions derived from our equation of state in conjunction with two advanced electrical conductivity models. Our results reveal that, while ion-ion association has a minimal influence on the modification of the predicted properties of sodium chloride solutions, their impact on sodium and magnesium sulfate solutions is considerably more noticeable.

BTZ black hole in [formula omitted] gravity and thermodynamic properties

In this study, we aim to investigate the rotating Banados-Teitelboim-Zanelli (BTZ) black hole (BH) solution within the framework of modified gravity theories. Notably, our investigation reveals that the BTZ BH space–time serves as a solution within the framework of Ricci-inverse (RI) gravity, particularly within Class-I models defined by f(R,A)=(R+αA). Here, R=gμνRμν and A=gμνAμν denote the Ricci and anti-curvature scalars, respectively, while α represents the coupling parameter. We show that this new modified theory induces modifications to the cosmological constant, demonstrating the influence of the coupling parameter α when analyzed in a vacuum as matter content. Additionally, we study the thermodynamic properties of this BTZ BH solution obtained within the RI-gravity framework and analyze the associated physical quantities. It is evident that the thermodynamic parameters, including BH horizons, Hawking temperature, entropy, free energy, internal energy, and specific heat capacity, undergo alterations due to the coupling constant α. Specifically, when α=0, our findings align with the outcomes documented in existing literature obtained in the general relativity (GR) context using the BTZ BH solution.

Dark energy and dark matter configurations for wormholes and solitionic hierarchies of nonmetric Ricci flows and F(R,T,Q,Tm)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$F(R,T,Q,T_{m})$$\\end{document} gravity

We extend the anholonomic frame and connection deformation method, AFCDM, for constructing exact and parametric solutions in general relativity, GR, to geometric flow models and modified gravity theories, MGTs, with nontrivial torsion and nonmetricity fields. Following abstract geometric or variational methods, we can derive corresponding systems of nonmetric gravitational and matter field equations which consist of very sophisticate systems of coupled nonlinear PDEs. Using nonholonomic frames with dyadic spacetime splitting and applying the AFCDM, we prove that such systems of PDEs can be decoupled and integrated in general forms for generic off-diagonal metric structures and generalized affine connections. We generate new classes of quasi-stationary solutions (which do not depend on time like coordinates) and study the physical properties of some physically important examples. Such exact or parametric solutions are determined by nonmetric solitonic distributions and/or ellipsoidal deformations of wormhole hole configurations. It is not possible to describe the thermodynamic properties of such solutions in the framework of the Bekenstein–Hawking paradigm because such metrics do not involve, in general, certain horizons, duality, or holographic configurations. Nevertheless, we can always elaborate on associated Grigori Perelman thermodynamic models elaborated for nonmetric geometric flows. In explicit form, applying the AFCDM, we construct and study the physical implications of new classes of traversable wormhole solutions describing solitonic deformation and dissipation of non-Riemannian geometric objects. Such models with nontrivial gravitational off-diagonal vacuum are important for elaborating models of dark energy and dark matter involving wormhole configurations and solitonic-type structure formation.

Application of CALPHAD Method for Predicting of Concentration Range of Amorphization of Transition Metals Melts

Early, the efficiency of the CALPHAD (Calculation of Phase Diagrams) method to a targeted search for compositions of amorphous alloys has been shown. The method for predicting the ranges of amorphization is based on the calculation of diagrams of metastable phase transformations between supercooled melts and boundary solid solutions on the base of pure elements. In this work, the model parameters for thermodynamic properties of liquid alloys and boundary solid solutions were summarized in a self-consistent database for the multicomponent Cu–Fe–Ni–Ti–Zr–Hf system. Such database for the multicomponent system is based on a common set of model parameters for boundary binary and ternary systems. This database was used to predict the concentration ranges of amorphization for the quinary Cu–Fe–Ni–Ti–Zr, Cu–Fe–Ni–Ti–Hf and boundary ternary and quaternary systems. The results of calculations are presented along sections in quaternary and quinary systems. The ternary and quaternary equiatomic alloys along with high entropy CuFeNiTiZr and CuFeNiTiHf alloys are trapped into prognosed composition ranges of amorphization. Predicted composition space of amorphization for melts of the Fe–Ni–Ti–Zr system is shown on the concentration tetrahedron. Based on the obtained results, a new criterion for predicting the concentration regions of amorphization of multicomponent melts is proposed, according to which the presence of a sufficient content of metals that are electron acceptors and donors is a chemical factor that affects the thermodynamic stability of melts and determines their glass-forming ability. For multicomponent melts of the Cu–Fe–Ni–Ti–Zr–Hf system the concentration ranges of amorphization correspond to the simultaneous fulfillment of the conditions xFe + xNi + xCu > 0.25 and xTi + xZr + xHf > 0.15, where Fe, Ni, and Cu are electron acceptors and Ti, Zr, and Hf are electron donors.

Химико-термодинамические свойства чистых и многокомпонентных растворов сахарозы

To select an optimal mode of evaporation and crystallization, sugar producers need comprehensive databases of chemical and thermodynamic properties of sucrose solutions. This article introduces refined experimental estimates of the chemical and thermodynamic properties of pure and technical multicomponent sucrose solutions. 
 The study involved a modernized ebulliometer with two circulation tubes that measured the true boiling points of concentrated and supersaturated homogeneous solutions, as well as heterogeneous crystallizing systems. The boiling points of pure and multicomponent sucrose solutions were observed for the following variables: 5–93% dry solids, 60–100% purity, 20–100 kPa.
 In this study, the sucrose solutions did not obey Raoult’s laws for ideal mixtures, while the Ramsay-Young’s equation and Dühring’s rule were approximate. The thermodynamic properties of these solutions fit in the Lewis theory of activity. The study yielded a new thermodynamic equation for the boiling point in pure and technical multicomponent sucrose solutions. The authors revealed the correlation between the constants of Ramsay-Young and Dühring and the concentration and supersaturation of sucrose solutions, as well as the change in the entropy of these solutions. The error of estimate was 2–3%. The supersaturation coefficient was measured by the ratio of the boiling points of the solution and water. 
 The authors used differential and relative ebulliometric criteria to develop some practical methods for monitoring and controlling the process of isobaric evaporative crystallization. The new method can improve the commercial mass sucrose crystallization from boiling solutions.

MD Simulation of Water Using a Rigid Body Description Requires a Small Time Step to Ensure Equipartition.

In simulations of aqueous systems, it is common to freeze the bond vibration and angle bending modes in water to allow for a longer time step δt for integrating the equations of motion. Thus, δt = 2 fs is often used in simulating rigid models of water. We simulate the SPC/E model of water using δt from 0.5 to 3.0 fs and up to 4 fs using hydrogen mass repartitioning. In these simulations, we find that for all but δt = 0.5 fs, equipartition is not obtained between translational and rotational modes, with the rotational modes exhibiting a lower temperature than the translation modes. To probe the reasons for the lack of equipartition, we study the autocorrelation of the translational velocity of the center of mass and the angular velocity of the rigid water molecule, respectively. We find that the rotational relaxation occurs on a timescale comparable to vibrational periods, calling into question the original motivations for freezing the vibrations. Furthermore, a time step with δt ≥ 1 fs is not able to capture accurately the fast rotational relaxation, which reveals its impact as an effective slowing-down of rotational relaxation. The fluctuation-dissipation relation then leads to the conclusion that the rotational temperature should be cooler for δt greater than the reference value of 0.5 fs. Consideration of fluctuation-dissipation in equilibrium molecular dynamics simulations also emphasizes the need to capture the temporal evolution of fluctuations with fidelity and the role of δt in this regard. The time step also influences the solution thermodynamic properties: both the mean system potential energies and the excess entropy of hydration of a soft repulsive cavity are sensitive to δt.

Effect of Lactate-Based Protic Ionic Liquids on the Thermodynamic and Transport Properties of Aqueous Lithium Bromide Solutions at Different Temperatures

Effect of Lactate-Based Protic Ionic Liquids on the Thermodynamic and Transport Properties of Aqueous Lithium Bromide Solutions at Different Temperatures

DFT Model of Elemental Sulfur in Sulfolane Solutions.

The structure and the thermodynamic and optical (UV) properties of elemental sulfur solution in sulfolane (Sl) have been studied using density functional theory methods. The cyclic molecular form of sulfur (S8 "crown") was found using PBE1PBE/6-311+G(d,p) approximation in combination with a polarizable continuum model (the integral equation formalism variant) to exist in sulfolane medium as a Sl-S8-Sl solvate. It has been theoretically established that sulfur can form stable (S8)n clusters in concentrated solutions. An increase in the extent of association (n) of the sulfur cluster leads to a decrease in the extinction coefficient [TD-DFT(TPSSTPSS/6-311+G(d,p))] of the most intense absorption maximum lying at about 50,000 cm-1 while maintaining the shape of the remaining part of the spectrum. The observed pattern qualitatively expresses the spectral regularities of solutions with different concentrations of sulfur in sulfolane. It has been proposed that a model of the absorption spectrum of elemental sulfur suggests a minor contribution of the S12 molecular form (G298°((S12)2) - G298°((S8)3) ≈ -15.5 kJ mol-1). The findings of the study will provide deeper insights into the transformation of molecular forms of sulfur and more precisely analyze processes involving sulfur as an acting species using electronic spectroscopy.

Gauss-Bonnet solution with a cloud of strings in de Sitter and anti-de Sitter space* *Supported by the National Natural Science Foundation of China (12275087) and the Fundamental Research Funds for the Central Universities.

In this study, we investigate exact spherically symmetric Gauss-Bonnet black hole solutions surrounded by a cloud of string fluid with the cosmological constant in dimensions. Both charged and uncharged cases are considered. We focus on the de Sitter solutions in the main text and provide the anti-de Sitter solutions in the appendix. We analyze the features of event horizons and thermodynamic properties of the black hole solutions. The mass, Hawking temperature, thermal stability, and phase transitions are discussed. Moreover, the equation of state and critical phenomena associated with these solutions are explored.

Modeling the effects of salt concentration on aqueous and organic electrolytes

Understanding the thermodynamic properties of electrolyte solutions is of vital importance for a myriad of physiological and technological applications. The mean activity coefficient γ± is associated with the deviation of an electrolyte solution from its ideal behavior and may be obtained by combining the Debye-Hückel (DH) and Born (B) equations. However, the DH and B equations depend on the concentration and temperature-dependent static permittivity of the solution εr(c, T) and the size of the solvated ions ri, whose experimental data is often not available. Here, we use a combination of molecular dynamics and density functional theory to predict εr(c, T) and ri, which enables us to apply the DH and B equations to any technologically relevant aqueous and nonaqueous electrolyte at any concentration and temperature of interest.

The new solid solution of double transition metal MXenes: Atomistic modeling of two-dimensional YScX (X= C and N)

In this paper, the structural and dynamical stability, electronic, optical, and thermodynamic properties of a new solid solution of two transition metals YScX (X = C and N) MXenes have been studied. The calculation is carried out based on density functional theory (DFT) and the pseudopotential technique. The results obtained from the structural, thermodynamical, and dynamical stability have shown that 2D YScC and YScN MXenes are structurally stable and their experimental synthesis is possible. Total density of states and band structure calculations show that YScX (X = C and N) MXene exhibits metallic behavior using LDA, GGA, and GGA + HSE06 approximations. According to the total density of states results, it can be concluded that the YScX MXenes have a pseudogap close to the Fermi level and at the left side, which justifies the structural stability of the studied monolayers. The plots of electron charge density distribution and electron localization function justify the metallic nature of the mentioned structures. The large negative values of the real part of the dielectric function indicate that 2D YScX (X = C and N) MXenes have a metallic Drude-like behavior. The saturation of the surface of 2D monolayers with various F, O, OH, and H functional groups does not change the metallic properties, the only exception that reveals the semiconductor property in the HSE06 method is YScCH2 Mxene where no atomic orbital intersects the Fermi level. In addition, the onset of the absorption spectrum of YScX (X = C and N) MXenes corresponds to zero photon energy, which is a confirmation of the metallic properties of the investigated structures. The GGA + HSE06 method enables faster electromagnetic beam propagation through the 2D materials, particularly in the x-direction of the hexagonal structure, resulting in a lower absorption coefficient and optical conductivity of 2D monolayers compared to the GGA method. The rising trend of entropy with temperature provides evidence for the endothermic behavior of YScC and YScN monolayers. Unlike heat capacity, the Debye temperature of YScX (X = C and N) MXenes decreases with respect to temperature T, according to the inverse relationship between the Debye temperature and the heat capacity. Due to structural and dynamic stability and layered structure with the nature of covalent and metallic bonds, YScX MXenes are a suitable choice for use in electrical connections and as a protective coating with a low friction level.

Solid-liquid phase equilibria and theoretical simulation of the quaternary system NaBr + KBr + MgBr2 + H2O and its subsystem NaBr + MgBr2 + H2O at 308.2 K and 1–500 bar

Solid-liquid phase equilibria of bromine salt can be indicative of Br evolution in Br-rich underground brines of Sichuan Basin in China. Consequently, the solid–liquid phase equilibria of the ternary subsystem NaBr + MgBr2 + H2O and quaternary system NaBr + KBr + MgBr2 + H2O at 308.2 K are determined by the isothermal dissolution equilibrium method. Then, Pitzer ion interaction model and particle swarm optimal algorithm are used to predict the phase equilibria of the systems listed above. The calculated solubilities are in good agreement with the experimental data.Considering the pressure conditions in deep strata, furthermore, we develop a thermodynamic prediction model of the phase equilibria for the systems changing with pressure. The thermodynamic volume properties of solution at 308.2 K with increasing pressure (1–500 bar) are evaluated. The unreported parameters of pressure dependency (Av,V¯MX(aq)0,βMX(0),v,βMX(1),v,CMXv) in Pitzer model at 308.2 K in the studied systems of this work are fitted accordingly. As a result, the effects of pressure on the phase equilibria are investigated in detail, and phase diagrams of the systems at 1–500 bar are also drawn and discussed. This work can provide important thermodynamic data for the salt mineral exploitation of the actual deep strata brines.

Equilibrium Solubility Behavior and Thermodynamic Properties of Potassium and Ammonium Di-Hydrogenophosphate Aqueous Solutions at T = 298.15 K

Equilibrium Solubility Behavior and Thermodynamic Properties of Potassium and Ammonium Di-Hydrogenophosphate Aqueous Solutions at <i>T</i> = 298.15 K

Speeds of Sound in Binary Mixtures of Water and Carbon Dioxide at Temperatures from 273 K to 313 K and at Pressures up to 50 MPa

Knowledge of thermodynamic properties of aqueous solutions of CO2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO2. We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO2 for mole fractions of CO2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO2. Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO2 gas.

Self-Consistent Implementation of a Solvation Free Energy Framework to Predict the Salt Solubilities of Six Alkali Halides.

To assess the salt solubilities of six alkali halides in aqueous systems, we proposed a thermodynamic cycle and an efficient molecular modeling methodology. The Gibbs free energy changes for vaporization, dissociation, and dissolution were calculated using the experimental data of ionic thermodynamic properties obtained from the NBS tables. Additionally, the Marcus' and Tissandier's solvation free energy data for Li+, Na+, K+, Cl-, and Br- ions were compared with the conventional solvation free energies by substituting into our self-consistent thermodynamic cycle. Furthermore, Tissandier's absolute solvation free energy data were used as the training set to refit the Lennard-Jones parameters of OPLS-AA force field for ions. To predict salt solubilities, an assumption of a pseudo-solvent was proposed to characterize the coupling work of a solute with its environment from infinitely diluted to saturated solutions, indicating that the Gibbs energy change of solvation process is a function of ionic strength. Following the self-consistency of the cycle, the newly derived formulas were used to determine the salt solubilities by interpolating the intersection of Gibbs free energy of dissolution and the zero free energy line. The refined ion parameters can also predict the structure and thermodynamic properties of aqueous electrolyte solutions, such as densities, pair correlation functions, hydration numbers, mean activity coefficients, vapor pressures, and the radial dependences of the net charge at 298.15 K and 1 bar. Our method can be used to characterize the solid-liquid equilibria of ions or charged particles in aqueous systems. Furthermore, for highly concentrated strong electrolyte systems, it is essential to introduce accurate water models and polarizable force fields.