Gibbs Free Energy Of Mixing Research Articles

Multi-technique approach to explore the mixed micellization behavior of promazine hydrochloride drug and cetyltrimethylammonium bromide surfactant in aqueous glycine, glycylglycine (dipeptide) and glycylglycylglycine (tripeptide) solutions

The aggregation properties of amphiphiles and their mixtures are of theoretical and applied importance. Therefore, mixed micellization behavior of promazine hydrochloride (PMZ) drug and cetyltrimethylammonium bromide (CTAB) surfactant at different mole fractions, α PMZ = (0.2, 0.4, 0.6 and 0.8) has been scrutinized in water and (0.025, 0.050 and 0.100) mol·kg −1 aqueous solutions of glycine, glycylglycine (dipeptide) and glycylglycylglycine (tripeptide) at T = (298.15 to 318.15) K, by means of multiple techniques. Thermodynamic parameters of micellization (ΔG°m, ΔH°m, and ΔS°m) along with excess Gibbs free energy of mixing (ΔG m ex), the molecular interaction parameter (β int), and the degree of ionization (α), have been attained from the conductivity measurements. The partial specific volumes (φ v), partial specific isentropic compression (φ κ) as well as isentropic compressibilities (κ s) were computed from the measured density and speed of sound data. UV-Visible absorption, fluorescence emission and proton (1H) NMR spectra were recorded for the pure PMZ and mixed (PMZ + CTAB) system in the presence of glycine(aq), glycylglycine(aq) and glycylglycylglycine(aq) solutions. Dynamic light scattering (DLS) study was carried out to measure the hydrodynamic diameters (D H) of mixed micellar systems. The prevalence of hydrophobic-hydrophobic interactions amid the hydrophobic groups of PMZ drug (tricyclic scaffolding), CTAB (–C16H33), glycine, di- and tri-peptides (–CH2), and electrostatic interactions amid the hydrophilic/ionic groups of PMZ{tertiary amine part and +NH (CH3)2, Cl−}, CTAB (–N (CH3)3 +, Br‒) and glycine, di- and tri-peptides {zwitterion (NH3 +, COO−} have been depicted from the aforementioned studies.

Experimental Method to Distinguish between a Solution and a Suspension

AbstractDispersion of objects in a fluid phase can be classified as solutions (Gibbs free energy of mixing, ΔGmix < 0) or suspensions (ΔGmix > 0) depending on their thermodynamic stability. Small objects tend to form solutions, larger ones suspensions, e.g., molecules versus micrometer‐sized colloids. Proteins and nanomaterials fall between these two size regimes. The long‐standing issue of whether proteins and nanoparticles are dissolved or suspended remains an important research question. Here, a simple, versatile, and experimentally robust method, based on sedimentation equilibrium analytical ultracentrifugation (SE‐AUC), which can determine whether proteins, nanoparticles, or polymers form solutions or suspensions, is presented. SE‐AUC determines the osmotic pressure profile for a dispersion. Such a profile for solutions (equilibrium one‐phase systems) is independent of the initial and the operating conditions. The opposite is true for suspensions that are nonequilibrium two‐phase systems. This study proves that bovine serum albumin and lysozyme form solutions while ferritin and apoferritin form suspensions.

Energetics of hydroxylbastnäsite solid solutions, La1−xNdxCO3OH

Bastnäsites (LnCO3(F,OH)) are a group of common rare earth elements (REE)-bearing minerals and are one of the primary global sources of REE. Due to the chemical similarities among REE, bastnӓsites tend to occur as solid solutions instead of end members in REE containing ores. To better understand the processes and the mechanisms of formation of such deposits, it is essential to determine the thermodynamic properties of bastnӓsites, including hydroxylbastnӓsite (LnCO3OH) solid solutions. In this work, we performed detailed structural and calorimetric investigations on synthetic hexagonal La–Nd hydroxylbastnӓsite (La1–xNdxCO3OH, x = 0, 0.25, 0.5, 0.75, 1) solid solutions. X-ray diffraction confirms the crystal structure of the solid solution series in the P6¯ space group, and pair distribution function (PDF) analysis reveals local bonding environments characterized by three different types of 9-coordinated metal-oxygen polyhedra. Unit cell parameters of La1–xNdxCO3OH exhibit a nearly linear relation with the Nd content x, suggesting a random distribution of La and Nd in the structure. Their standard enthalpies of formation (ΔH°f) were determined by high temperature oxide melt drop solution calorimetry, from which the enthalpies of mixing (ΔHmix) were derived. The ΔHmix can be fitted by a regular solution model with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting enthalpic metastability of La1–xNdxCO3OH relative to the two endmembers. Combining entropy and enthalpy, we further estimated the Gibbs free energies of mixing (ΔGmix) at relevant temperatures, revealing favorable temperatures under which the intermediate La1–xNdxCO3OH phases can be stabilized. Such entropy-driven stabilization, as is consistent with our geochemical modeling results, may explain the enhancement of thermal stability of the solid solutions in nature. Additionally, the temperature range constrained from this study may be used to estimate the thermal history of REE bastnӓsite deposit.

Enthalpy driving force and chemical bond weakening: The solid-solution formation mechanism and densification behavior of high-entropy diborides (Hf1−x/4Zr1−x/4Nb1−x/4Ta1−x/4Scx)B2

(Hf0.2Zr0.2Nb0.2Ta0.2Sc0.2)B2 was designed to improve the densification and solid-solution formation of high-entropy transition metal diborides, and its phase stability was predicted using the energy distribution of the local mixing enthalpy of all possible configurations. It was found that (Hf0.2Zr0.2Nb0.2Ta0.2Sc0.2)B2 are enthalpy-stabilized materials. The two-component metal diborides formed by transition metal diborides (HfB2, ZrB2, TaB2 and NbB2) with ScB2 are thermodynamically favorable, based on the mixing enthalpy. Therefore, the introduction of ScB2 in high-entropy metal diborides is beneficial to reduce the mixing Gibbs free energy during the boro/carbothermal reduction process, which enables the formation of single-phase solid solution at low temperatures. Even high-entropy metal diboride powders with large particle sizes, 25–57 µm, can achieve sintered density up to ~97% due to the introduction of ScB2 in high-entropy metal diborides, owing to its weakening action on the TM d - B p and the TM dd bonding.

1,3 Dialkylated Imidazolium Ionic Liquid Causes Interdigitated Domains in a Phospholipid Membrane.

Amphiphilic imidazolium-based ionic liquids (ILs) have proven their efficacy in altering the membrane integrity and dynamics. The present article investigates the phase-separated domains in a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membrane induced by 1,3 dialkylated imidazolium IL. Isotherm measurements on DPPC monolayers formed at the air-water interface have shown a decrease in the mean molecular area with the addition of this IL. The positive value of the excess Gibbs free energy of mixing indicates an unfavorable mixing of the IL into the lipid. This leads to IL-induced phase-separated domains in the multilayer of the lipid confirmed by the occurrence of two sets of equidistance peaks in the X-ray reflectivity data. The electron density profile along the surface normal obtained by the swelling method shows the bilayer thickness of the newly formed IL-rich phase to be substantially lower (∼34 Å) than the DPPC phase (∼45.8 Å). This IL-rich phase has been confirmed to be interdigitated, showing an enhanced electron density in the tail region due to the overlapping hydrocarbon chains. Differential scanning calorimetry measurements showed that the incorporation of IL enhances the fluidity of the lipid bilayer. Therefore, the study indicates the formation of an interdigitated phase with a lower order compared to the gel phase in the DPPC membrane supplemented with the IL.

Entropy determination for mixtures in the adiabatic grand-isobaric ensemble.

The entropy change that occurs upon mixing two fluids has remained an intriguing topic since the dawn of statistical mechanics. In this work, we generalize the grand-isobaric ensemble to mixtures and develop a Monte Carlo algorithm for the rapid determination of entropy in these systems. A key advantage of adiabatic ensembles is the direct connection they provide with entropy. Here, we show how the entropy of a binary mixture A-B can be readily obtained in the adiabatic grand-isobaric (μA, μB, P, R) ensemble, in which μA and μB denote the chemical potential of components A and B, respectively, P is the pressure, and R is the heat (Ray) function, that corresponds to the total energy of the system. This, in turn, allows for the evaluation of the entropy of mixing and the Gibbs free energy of mixing. We also demonstrate that our approach performs very well both on systems modeled with simple potentials and with complex many-body force fields. Finally, this approach provides a direct route to the determination of the thermodynamic properties of mixing and allows for the efficient detection of departures from ideal behavior in mixtures.

Evaluation of thermophysical properties of the LiCl-KCl system via ab initio and experimental methods

Molten Salt Reactors (MSRs) are envisioned as a potential pathway to safer, more economical nuclear electricity generation and supply of industrial heat. MSRs under consideration today are either solid-fueled salt-cooled designs or liquid-salt-fueled designs with chloride or fluoride based salts. A significant knowledge gap exists in the data for the fundamental properties relevant to fuels and coolants for MSRs that needs to be addressed in order to expedite the technical readiness level of the MSR design concepts. With the rapid development and improvement of computational materials science, computational methods such as Density Functional Theory (DFT) calculations and ab initio Molecular Dynamics (AIMD) simulations are widely used as an effective and reliable tool to investigate the atomic interaction in materials. In this article, the density of the LiCl-KCl system was determined via AIMD calculations and verified using new experimental analyses. AIMD was further utilized to calculate the compressibility , heat capacity, enthalpy of mixing, and Gibbs free energy of mixing. This work spans a wider range of compositions and temperatures than have previously been explored computationally for this pseudo-binary system and provides the basis for further advanced thermophysical property evaluation utilizing AIMD methods.

Reliable estimate of minimum miscibility pressure from multiple possible EOS models for a reservoir oil under data constraint

Multiple Equation of State (EOS) models are possible for a reservoir oil if limited laboratory data is used in the EOS model development; each EOS model has its own predicted minimum miscibility pressure (MMP) value with unknown reliability. This article presents a novel approach to estimate a reliable MMP value using the multiple MMP values calculated from multiple EOS models developed with limited laboratory data such as bubble point and density at bubble point. MMP predicted using the proposed approach has better accuracy than the estimated MMP from an EOS model developed using a large set of data at the regression stage. Each possible EOS model for a reservoir oil has a specific set of values of total Gibbs free energy of mixing (g) at bubble point and predicted MMP for a given injection gas. The MMP estimate is developed using the trend of g versus MMP (predicted) from multiple EOS models in the proposed approach. The AARD in MMP prediction for 22 oils is 5.21% using SRK EOS and 6.65% using PR EOS, which is lower than the earlier approach (7.6%) that uses all PVT, swelling test, and multi-contact test data in EOS model development.

Machine Learning-Driven High-Throughput Screening of Alloy-Based Catalysts for Selective CO2 Hydrogenation to Methanol

The revolutionary development of machine learning and data science and exploration of its application in material science are huge achievements of the scientific community in the past decade. In this work, we have reported an efficient approach of machine learning-aided high-throughput screening for finding selective earth-abundant high-entropy alloy-based catalysts for CO2 to methanol formation using a machine learning algorithm and microstructure model. For this, we have chosen earth-abundant Cu, Co, Ni, Zn, and Mg metals to form various alloy-based compositions (bimetallic, trimetallic, tetrametallic, and high-entropy alloys) for selective CO2 reduction reaction toward CH3OH. Since there are several possible surface microstructures for different alloys, we have used machine learning along with DFT calculations for high-throughput screening of the catalysts. In this study, the stability of various 8-atom fcc periodic (111) surface unit cells has been calculated using the atomic-size difference factor (δ) as well as the ratio taken from Gibbs free energy of mixing (Ω). Thinking about the simplicity and accuracy, microstructure models by considering the neighboring atoms of the adsorption sites and others as Cu atoms have been considered for different adsorption sites (on-top, bridge, and hollow-hcp). Moreover, the adsorption energies of the *H, *O, *CO, *HCO, *H2CO, and *H3CO intermediates have been predicted using the best fitted algorithm of the training set. The predicted adsorption energies have been screened based on the pure Cu adsorption energy. Furthermore, the screened catalysts have been correlated among different adsorption site microstructures. At the end, we were able to find seven active catalysts, among which two catalysts are CuCoNiZn-based tetrametallic, three catalysts are CuNiZn-based trimetallic, and two catalysts are CuCoZn-based trimetallic alloys. Hence, this work demonstrates not an ultimate but an efficient approach for finding new product-selective catalysts, and we expect that it can be convenient for other similar types of reactions in forthcoming days.

Influence of atomic-scale structure on the transport, ordering, and thermodynamics of partially ordered Cu-In alloys

We demonstrate the atomic-level structural properties of liquid Cu-In alloy as a function of In concentration using Square-Well (SW) model potential function under random phase approximation. It was found that the concentration-dependent structure factor S(k) and its Fourier transform, radial distribution function g(r) are in good agreement with the results obtained by the X-ray diffraction technique. Transport coefficients like diffusion coefficient and shear viscosity of liquid Cu-In alloys were estimated through computed structural functions and SW potential function. Interdiffusion coefficients in the melts were computed by solving the well-known Einstein's equation for Brownian particles with SW pair potential under linear trajectory principal. The composition-dependent shear viscosity is calculated using computed diffusion data in modified Stokes-Einstein (SE) relation. Specifically, we demonstrate a breakdown of SE relation at low In concentration in liquid Cu-In alloy. Using model calculations, we investigate the thermodynamic properties of alloy such as enthalpy of mixing, Gibbs free energy of mixing, and entropy of mixing. The concentration-concentration fluctuation at the zero momentum vector SCC(0)shows that there is a strong chemical bond between hetero-atoms in the Cu-rich region of liquid Cu-In alloys. It is worth mentioning here that the computed values of SCC(0), without using any adjusting or experimental parameter are in excellent agreement with experimental values measured by activity data.

Theoretical assessment for the mixing properties of AlMg liquid alloys at 1073K

The alloying behavior of AlMg alloy in the liquid form at 1073 K has been theoretically investigated in the framework of four-parameter model which is based on Maclaurin series. The analytical expressions for thermodynamic functions such as excess free mixing energy, free mixing energy, enthalpy of mixing and entropy of mixing and microscopic functions such as concentration fluctuations at the long wavelength limit and Warren-Cowley chemical short range order parameter have been derived. These expressions have been used to compute the excess Gibbs free energy of mixing, Gibbs free energy of mixing, activity, enthalpy(heat) of mixing, excess entropy of mixing, entropy of mixing, concentration fluctuations in long wavelength limit and Warren-Cowley short range order parameters of AlMg liquid alloys at 1073 K. The investigation shows the excellent concurrence between the experimental and theoretical measurements of the mixing properties of AlMg liquid alloys at 1073 K. Interaction parameters of energy depends on temperature.

High entropy alloys and thermodynamically derived high stability alloys; a compositional comparative study of all 3–7 element systems composed of ten 3d metals at 1273 K

Studies of high entropy or multi-principal element alloys are focused mainly on equimolar or near-equimolar compositions for which configurational entropy is maximized. Negligence of interactions between elements forming such alloys, namely enthalpy of mixing, may detract these studies from a desirable target, which is a stabilization of single-phases instead of intermetallic compounds. In this work, both entropy and enthalpy terms are taken into account for the determination of the high stability compositions, for which the Gibbs free energy of mixing is minimized. For the ten 3d metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Al) all possible combinations forming 3- (120 compositions), 4- (210), 5- (252), 6- (210) and 7-component systems (120) are analyzed. Two numerical methods: a genetic algorithm (GA) and a hybrid one (a combination of GA with the gradient method) give convergent results regarding the high stability compositions at 1273 K (a typical temperature used on HEAs synthesis). It is found surprisingly that such compositions are dominated by the Ti and Al or Ni contents with minor ones of the seven remaining elements, especially for 6 and 7-component systems. These numbers can be related to average parameters of interaction (of a given element with the remaining ones) giving almost monotonic dependence; the lower the average value of the interaction parameter of a given element − the higher its content in the alloys of the high stability. Such selective preferences in compositions are reflected by high deviations between the high stability compositions and equimolar ones, with an average reaching 48% for ternary systems to 105% for 7-component alloys (expressed as normalized root mean square errors).

Effect of fluorocarbon surfactants on the adsorption of hydrocarbon surfactants mixture at the water-air interface

Taking into account the great practical importance of the surface tension of the aqueous solution of multicomponent surfactant mixtures their adsorption at the water-air interface and the composition of the adsorbed monolayer were considered. For this consideration the mixture of the p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycol) Triton X-165 (TX165) and hexadecyltrimethylammonium bromide (CTAB) with FC6EO14 as well as with FC5EO10 was applied. The surface tension of the studied solution at the constant CTAB and TX165 binary mixture concentration corresponding to its solution surface tension equal to 60 and 50 mN/m and changing fluorocarbon surfactant concentration was measured. The obtained results were described by the exponential function of the second order and predicted by the modified Fainerman and Miller equation. To solve the Fainerman and Miller equation the fraction of adsorbed mixed monolayer at the water-air interface occupied by particular surfactants was determined. For its determination, the contribution of particular surfactants in the mixture to reduction of water surface tension was taken into account. The fraction occupied by the given surfactant in the mixed monolayer was compared to that determined using the Hua and Rosen equation obtaining good agreement between them. The fraction of the mixed monolayer occupied by a given surfactant was also successfully used to solve the Gibbs and Frumkin equations for determination of surface concentration of a particular surfactant in the mixed monolayer. Based on the isotherms of the surface excess concentration as well as the Hua and Rosen theory the packing of the mixed monolayer and the presence of the synergetic effect in the reduction of water surface tension were deduced. This effect was also reflected in the standard Gibbs free energy of adsorption of surfactant mixtures at the water-air interface. It was found that this energy can be predicted based on this energy for particular surfactants of the mixture and Gibbs free energy of mixing.

Design of Composites by Infiltration Process: A Case Study of Liquid Ir-Si Alloy/SiC Systems.

The design of processing routes involving the presence of the liquid phase is mainly associated with the knowledge of its surface and transport properties. Despite this need, due to experimental difficulties related to high temperature measurements of metallic melts, for many alloy systems neither thermodynamic nor thermophysical properties data are available. A good example of a system lacking these datasets is the Ir-Si system, although over the last fifty years, the structures and properties of its solid phases have been widely investigated. To compensate the missing data, the Gibbs free energy of mixing of the Ir-Si liquid phase was calculated combining the model predicted values for the enthalpy and entropy of mixing using Miedema’s model and the free volume theory, respectively. Subsequently, in the framework of statistical mechanics and thermodynamics, the surface properties were calculated using the quasi-chemical approximation (QCA) for the regular solution, while to obtain the viscosity, the Moelwyn-Hughes (MH) and Terzieff models were applied. Subsequently, the predicted values of the abovementioned thermophysical properties were used to model the non-reactive infiltration isotherm of Ir-Si (eutectic)/SiC system.

Estimation of lurasidone hydrochloride equilibrium solubility in a polymeric solid dispersion using thermal analysis and thermodynamic modeling

Information on drug equilibrium solubility is crucial in producing a stable drug product, prolonging its shelf-life and maintaining its reported properties. Such data regarding the antipsychotic drug lurasidone hydrochloride (LRS HCl), were non-existent up to this date. We have presented results that could facilitate the formation of stable LRS HCl solid dispersions using amorphous poly(vinyl-pyrrolidone) (PVP) as a carrier. For the purpose of drug solubility enhancement, solid dispersions with different drug loads were prepared by solvent evaporation method and characterized by thermogravimetric analysis, differential scanning calorimetry, and Fourier-transform infrared spectroscopy (FT-IR). Thermal analysis has been used to detect the changes in heat capacity (cp ) occuring upon formation of a binary drug-polymer solid dispersion. Thermodynamic model accounting for those cp changes is used to estimate the Gibbs free energy of mixing (G M) and thus the equilibrium solubility of LRS HCl in PVP solid dispersions.

Solubility measurement and thermodynamic correlation of (2,4-dichlorophenoxy)acetic acid in fifteen pure solvents

The solid-liquid equilibrium behavior of (2,4-dichlorophenoxy)acetic acid (2,4-D) was investigated. The solubility of 2,4-D in fifteen pure solvents were measured using the gravimetric method from 278.15 K to 323.15 K. The Hirshfeld surface analysis provided quantitative information about intermolecular interactions in 2,4-D crystal structure. The MEPs analysis showed that the carboxyl group of 2,4-D molecule was the main site for hydrogen bond formation. Besides, four thermodynamic models including the modified Apelblat equation, van’t Hoff equation, λh equation, and NRTL model were used to correlate the solubility data, and the results showed that the modified Apelblat equation has the best fitting. The calculation results of thermodynamic properties such as mixing enthalpy, mixing entropy and mixing Gibbs free energy showed that the dissolution process of 2,4-D was spontaneous. KAT-LSER model was used to investigate the solvent effect. The results revealed that solvent-solvent interaction had a significant unfavorable effect to the solubility of 2,4-D. Finally, solvation free energy analysis was performed to quantitatively explain the differences in solubility of 2,4-D in different solvents.

First-Principle Study on the Stability of Lightly Doped (Nb1-x Ti x )C Complex Carbides and Their Verification in 1045 Steel.

The mixing Gibbs free energy and formation enthalpy difference of different Ti-doped (Nb1–xTix)C complex carbides were calculated using the Cambridge Serials Total Energy Package (CASTEP) module of Materials Studio 2019 software. The calculation results predict that (Nb1–xTix)C complex carbides have higher stability than pure NbC and TiC. Therefore, three lightly Ti-doped (Nb1–xTix)C complex carbides with theoretical densities close to that of the 1045 steel were designed for calculations. The calculation results show that the formation energy of (Nb1–xTix)C complex carbides decreases with an increase in the Ti content. These designed (Nb1–xTix)C complex carbides have mechanical stability, and their bulk modulus, shear modulus, Young’s modulus, and hardness are all lower than those of pure NbC. The electronic performance results show that these three structures show good conductivity, and the 3d orbitals of Ti atoms and the 4d orbitals of Nb atoms are strongly hybridized with the 2p orbitals of C atoms. The Nb–C and Ti–C bonds exhibit strong covalent bonds. To verify the stability of the (Nb1–xTix)C complex carbides, the prepared (Nb0.8Ti0.2)C complex carbide was added to the 1045 steel as a refiner. After observing under a transmission electron microscope (TEM), we found that the (Nb0.8Ti0.2)C complex carbide could exist stably as a face-centered cubic structure, which provided a method for the design and synthesis of complex carbides used for refiners.

Evaluations of adsorbents and salt-methanol solutions for low-grade heat driven osmotic heat engines

To recovery low temperature waste heat, a methanol-based adsorption-driven osmotic heat engine is investigated, which consists of an adsorption-based desalination system for producing concentrated and diluted solutions, and a pressure retarded osmosis system for extracting power from the Gibbs free energy of mixing. Salt-Methanol is used as working solution and the activated carbons and metal-organic frameworks are employed as the adsorbents. Impacts of desorption temperature, salt concentrations, salt types, and adsorbents on the system performance are numerically analyzed. Criteria for screening the adsorbents and salts are evaluated and discussed. Qualified adsorbents should have larger relative pressure where half of the maximum absorption uptake is achieved and moderate adsorption enthalpy. Salt-methanol solutions with larger solubility and osmotic coefficient are beneficial for improving the system energy efficiency. When operating between 60 °C and 20 °C, a maximum energy efficiency of 6.68% was achieved at 5 mol/kg LiBr-methanol solution for MAXSORB3 as the adsorbent with one-stage solid porous matrix regenerator employed. This study contributes to methanol-based adsorption-driven osmotic heat engines for efficient heat to electricity conversion, as well as providing criteria for selecting appropriate adsorbents.

Study of excess free energy of mixing and heat of mixing of liquid ternary Al–Li–Zn alloy by assessing the thermodynamic properties of sub-binary alloys

The exponential temperature-dependent interaction parameters of the Redlich-Kister (R–K) polynomial for the binary sub-systems of the liquid Al–Li–Zn ternary alloy were optimized using available literature data. The ternary interaction terms of the Redlich-Kister-Maggianu (R–K–M) polynomial were then optimized in order to determine the excess Gibbs free energy of mixing (GMxs) and the enthalpy of mixing (HM) of the system. These functions for the liquid ternary alloys were also computed at temperatures of 973 K, 1273 K and 1573 K. The calculated inverted miscibility gap that appeared in GMxs while using the linear temperature-dependent interaction parameters was suppressed in this work by the assumption of the interaction parameters to be exponential temperature dependent. The enthalpy of mixing of the alloy so calculated was found to be in good agreement with the available experimental data.

Study of artifacts in thermodynamic and structural properties of Li–Mg alloy in liquid state using linear and exponential models

Temperature-dependent interaction parameters of Redlich-Kister (R–K) polynomials for Li–Mg alloy in liquid phase have been optimized using experimental data in the framework of linear and exponential models. These parameters have then been used to compute the thermodynamic properties (excess Gibbs free energy of mixing, enthalpy of mixing and activity) and structural property (concentration fluctuations in the long-wavelength limit) of the alloy at temperatures 1000 K, 1300 K, 1600 K, 1900 K, and 2200 K. The negative values of excess Gibbs free energy of mixing computed using linear T-dependent parameters increases with the rise in the temperature of the system beyond 1000 K while the same physical quantity computed using the exponential T-dependent interaction parameters decreases with the rise in temperatures and does not show any unusual trends up to 2200 K. Similar behavior has been found in the case of other thermodynamic and structural functions. The unusual behavior that appears in the thermodynamic and structural functions computed using linear T-dependent parameters can be eliminated if these functions are computed using exponential T-dependent parameters.