Molar Entropy Change Research Articles

Deciphering the spectroscopic and thermodynamic aspects of binding of biologically important antioxidants with the alkali induced state of human serum albumin.

Protein-ligand interactions are crucial for developing and identifying novel therapeutic targets. In this study, we investigate the interaction of the alkali induced state of human serum albumin (pH 11.2) with three hydroxycinnamic acid derivatives (HCDs), ferulic acid (FA), sinapic acid (SA) and trans-o-coumaric acid, which are biologically important antioxidants, and compare the outcomes with the results obtained at physiological pH (7.4). This study aims to explore the interaction of altered protein conformation with small molecules. Spectroscopic characterization methods show that the conformation of HSA and the ionic properties of HCDs are pH-dependent. Fluorescence, FRET and lifetime measurements reveal that the binding of HCDs with HSA is different at both pH 7.4 and 11.2. Despite the moderate binding of HCDs to HSA, circular dichroism and thermal denaturation studies report no conformational changes in HSA in the presence of HCDs. Isothermal titration calorimetry is employed to assess their binding based on structure and energetics using thermodynamic parameters. Standard molar enthalpy change (ΔH0m) and standard molar entropy change (ΔS0m) values vary with the change of pH from 7.4 to 11.2 with the contributions from the exothermicity and hydrophobicity of functional and aromatic groups of HCDs. Ferulic acid (FA) and sinapic acid (SA) binding to HSA is entropically driven, whereas trans-o-coumaric acid (CA) acid binding is enthalpically favourable. Our ITC studies also reveal that the involvement of -OH functional groups present in CA in binding with HSA is greater than that present in FA and SA at pH 11.2. Overall, this experimental study shows the comparable binding strength of HCDs to both the alkali-induced state of HSA and native HSA (pH 7.4). However, the mechanism of their binding is different.

Experimental and Computational Characterisation of the Molecular Interactions between 1‐Butyl‐1‐methyl‐pyrrolidin‐1‐ium bis(trifluoromethanesulphonyl)imide and Human Serum Albumin

AbstractRecently, ionic liquids (ILs) have emerged as a therapeutic agent for industrial‐based pharmacology. In this regard, the current study highlights the key aspects of IL, (1‐butyl‐1‐methyl‐pyrrolidine‐1‐ium bis(trifluoromethanesulphonyl)imide), [Pyr C4 NTf3−] such as pharmacodynamics and pharmacokinetics. We performed a detailed experimental and computational analysis of [Pyr C4 NTf3−] with human serum albumin (HSA) using various spectroscopic techniques viz. UV‐vis, steady‐state fluorescence, synchronous fluorescence, time‐resolved fluorescence, steady‐state anisotropy and tensiometry study along with molecular docking. Absorption and emission spectral studies revealed the complex formation between [Pyr C4 NTf3−] and HSA where the binding constant (Kb) was found to be 5.5×103 Lmol−1. Thermodynamic parameters, Gibb's free energy change (ΔG), molar enthalpy change (ΔH), and molar entropy change (ΔS) revealed that the complex formation process is spontaneous, and enthalpy driven where involvement of hydrogen bond and van der Waal forces play a major role. Further, CD spectroscopy and ANS experiment showed the stability of HSA in presence of [Pyr C4 NTf3−]. A site marker study suggested that the binding of [Pyr C4 NTf3−] occurred at site II in HSA which is well supported by a molecular docking study. Also, MD simulation was done which revealed the stability of the complex formed between HSA and [Pyr C4 NTf3−]. The study might help in utilizing [Pyr C4 NTf3−], IL as a therapeutic agent in the pharmaceutical industries.

Solubility measurement, correlation, and dissolution thermodynamics of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane · 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (2HNIW·HMX) co-crystal in two binary solvent mixtures

The solubility of 2HNIW·HMX co-crystal in two binary solvent mixtures (ethanol + methyl acetate, and 1,2-dichloroethane + methyl acetate) was measured by gravimetric method at various temperatures (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15 K) under atmospheric pressure (0.1 MPa). The experimental results revealed that the solubility for co-crystal in binary solvent mixtures is a simple function of ethanol (or 1,2-dichloroethane) mass fraction and temperature, which decreased with increasing temperature and mass fraction of ethanol (or 1,2-dichloroethane) in the binary solvent mixtures. The solubility of 2HNIW·HMX co-crystal was correlated with the modified Apelblat equation, CNIBS/R-K model, Jouyban-Acree-van't Hoff model, and Jouyban-Acree-Apelblat model. The fitting results demonstrate that the modified Apelblat model and CNIBS/R-K model provided a better correlation with the experimental results than the other models. Furthermore, the van’t Hoff equation was used to study the thermodynamic properties of the 2HNIW·HMX co-crystal dissolution process, including the apparent molar enthalpy change (ΔdisH°), the apparent molar entropy change (ΔdisS°), and the apparent molar Gibbs free energy change (ΔdisG°). The results show that the dissolution of the co-crystal in the selected binary solvent mixture is an exothermic process. The experimental and calculated solubility data and thermodynamic properties of the 2HNIW·HMX co-crystal would be helpful for selecting the appropriate solvent system for the reaction, crystallization, and purification of the 2HNIW·HMX co-crystal.

Frequency Responses of Molar Electrochemical Peltier Heat and Entropy Changes Analyzed as Thermometric Transfer Functions

In honor of Prof. Dr. Fritz Scholz in his recent retirement.This work proposes a theoretical framework to obtain the frequency response of molar electrochemical Peltier heat and entropy changes induced by a modulated electrical signal. This is based on an internal energy balance developed for a working electrode thermistor in ac regime. Then, from an analysis that correlates the electrochemical impedance and the interfacial temperature variation, two new transfer functions that depend on the frequency named as entropy changes and molar electrochemical Peltier heat, are obtained. This strategy is tested in two electrochemical systems: the ferrocyanide/ferricyanide couple and the copper ions in an acid sulphate-chloride medium. Both systems are analyzed by dc thermometric measurements, electrochemical impedance spectroscopy and ac-thermometric experiments namely variation of interfacial temperature. As a result, and are obtained and their values are correlated to the relaxation processes involved in the electrochemical reaction. Additionally, a brief discussion is included concerning the differences between the classical dc thermoelectrochemical methodology and the proposed approach here.

Computational design and screening of promising energetic materials: The coplanar family of novel heterocycle‐based explosives

AbstractA series of coplanar compounds based on triazine ring and triazole ring are proposed for the design of new energetic materials. The molecular structure, electronic structure, stability and detonation properties of these 40 compounds have been calculated by the density functional theory method. With the participation of hydroxyl, amino and nitro groups, these nitrogen‐rich fused ring compounds have the characteristics of aromaticity and hydrogen bonding. At the same time, the standard molar heat capacity, standard molar entropy and standard molar enthalpy change trends of some representative compounds in the temperature range of 200–800 K were calculated. The detonation performance, stability and density of these coplanar compounds were compared. There are 25 compounds with high density (ρ = 1.80–1.94 g·cm−3), of which A3‐2 exhibits excellent detonation performance (ρ = 1.93 g·cm−3, D = 8.86 km·s−1, P = 36.27 GPa), it is a potential candidate for high energy density materials. These research results provide a theoretical basis for the future design and screening of new energetic materials.

Solubility Measurements and Thermodynamic Properties of Sorbic Acid in Binary Solvent Mixtures of (Ethanol, 1-Propanol or 2-Propanol + Water) from 283.15 to 323.15 K

The solubility data of sorbic acid in binary systems of (ethanol + water), (1-propanol + water) and (2-propanol + water) were measured from 283.15 to 323.15 K using the static equilibrium method under atmospheric pressure. It was found that the solubility of sorbic acid in the three binary solvent systems increased with increasing temperature as well as increasing initial mole fraction of organic solvent in these systems. The van’t Hoff–Jouyban–Acree model, the modified Apelblat–Jouyban–Acree model and the CNIBS/R-K model were proposed for correlating the experimental solubility values in various solution systems. Furthermore, the dissolution thermodynamic properties of Gibbs energy change (ΔsolGo), molar enthalpy change (ΔsolHo) and molar entropy change (ΔsolSo) were calculated from the experimental solubility data, using the van’t Hoff equation. The positive values of ΔsolGo, ΔsolHo and ΔsolSo indicate that these dissolution processes of sorbic acid in the solvents studied were all endothermic and entropically favorable. In addition, the change of dissolution enthalpy was the main contributor to the positive value of the molar Gibbs energy of the dissolution process. The experimental solubility and the models used in this work would be conducive to purifying sorbic acid from its crude mixtures.

Thermodynamic modelling, Hansen solubility parameter and solvent effect of oxaprozin in thirteen pure solvents at different temperatures

The solubility of oxaprozin in thirteen organic solvents (methanol (MeOH), ethanol (EtOH), n-propanol (n-PrOH), n-butanol (n-BuOH), n-pentanol (n-PeOH), methyl acetate (MeAC), ethyl acetate (EtAC), n-propyl acetate (n-PrAC), n-butyl acetate (n-BuAC), n-amyl acetate (n-AmAC), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO)) was determined using a laser monitoring method at atmospheric pressure in this work. The measured temperature range for all selected solvents is 278.15 K to 323.15 K except DMSO 293.15 K to 323.15 K. Through the entire studied temperature range, the results turned out that oxaprozin solubility in selected solvents has a positive correlation with temperature variation. Four mathematical models were employed to correlate the solubility data including two empirical models (modified Apelblat model, λh model) and two activity coefficient models (UNIQUAC model, NRTL model), with the modified Apelblat model giving the best regression. Solubility order of oxaprozin in thirteen solvents was analysed by using the Hansen solubility parameter (HSP) and the solvent effect (solvent interaction) was investigated through correlating oxaprozin solubility in selected solvents based on KAT-LSER model. Moreover, according to van’t Hoff equation, thermodynamic properties including apparent standard molar enthalpy change (ΔsolH °), apparent standard molar Gibbs energy change (ΔsolG°) and apparent standard molar entropy change (ΔsolS) of the dissolution process of oxaprozin were also calculated and discussed.

Low-temperature heat capacity of d-glucose and d-fructose

The thermodynamics data of crystalline states of two representative components in blood sugar, d-glucose and d-fructose, are significant in researching artificial synthesis and composition transformation in vivo. The heat capacities of d-glucose and d-fructose over a temperature range of 1.9–300 K were measured and calculated by the heat capacity measurement module of physical property measurement system (PPMS). The heat capacities of two compounds increased steadily with temperature, showing a smooth curve without any thermal anomalies. The heat capacity of d-glucose is greater than that of d-fructose in the range of 0 K < T < 80 K, which is smaller than that of d-fructose between 80 and 300 K. Based on the lattice vibration mode, factors of generating the difference heat capacity data between the two isomers were investigated. Additionally, the heat capacity data were fitted by low-temperature heat capacity theoretical model. The thermodynamic data that molar entropy change and molar enthalpy change over the temperature range of 0–300 K were calculated. The standard molar entropy of d-glucose and d-fructose at 298.15 K was calculated by heat capacity fitting to be 214.64 and 217.56 J K−1 mol−1, all with an error of 0.21.

The Highly Efficient Absorption of CO2 by a Novel DBU Based Ionic Liquid

A novel anion-functionalized protic ionic liquid (IL), [DBUH][Triz], has been synthesized from 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (Triz). Density (ρ) and viscosity (η) of [DBUH][Triz] at different temperatures have been measured and the influence of temperature has been analyzed quantitatively. Then, the applications of [DBUH][Triz] in CO2 absorption have been investigated. It has been detected that this ionic liquid, which was easily prepared, shows excellent reversibility and a high absorption capacity, about 1.5 mol CO2 per 1 mol of IL (about 0.3 g CO2 per 1 g of IL). In addition, the influence of temperature, pressure and moisture on the absorption performance of [DBUH][Triz] has been studied separately, indicating that absorption is promoted by lower temperature and higher CO2 pressure. In addition, the mechanism of chemical absorption at two active sites has been deduced based on quantum-chemical calculations and 13C NMR spectra coupled with IR spectra. Furthermore, the equilibrium constant of chemical absorption (K) was calculated from the CO2 capacity at different temperatures (T) and a good linear relationship between the natural logarithm of the equilibrium constant ln K and 1/T was obtained with R2 of 0.996. From the slope and intercept of the fitted straight line, the molar reaction enthalpy change (ΔrHm) and molar reaction entropy change (ΔrSm) were analyzed, indicating that the capture of CO2 is an exothermic process and the IL–CO2 complex is less ordered than the pure ionic liquid.

Adsorption selectivity of cubic nano-CeO2 and effect of particle size on adsorption thermodynamics

Nanoparticles can effectively remove organic dyes from wastewater due to their excellent adsorption performances which are closely related to particle size. Herein, the relations between the thermodynamic properties and the particle size were deduced, and the influence mechanisms were also discussed. Then the adsorptions of four dyes on cubic nano-CeO2 were investigated. We found that cubic nano-CeO2 has strong adsorption selectivity for four dyes and the size dependence of the adsorption thermodynamic properties. This strong selectivity is attributed to electrostatic interaction and hydrogen bonding. Furthermore, with the particle size decreasing, the logarithm of standard adsorption equilibrium constant (lnKo) increase, while the standard molar Gibbs energy change of adsorption (ΔadsGmθ), the standard molar adsorption enthalpy change (ΔadsHmθ) and the standard molar adsorption entropy change (ΔadsSmθ) decrease, and there are good linear relationships between this thermodynamic properties and the reciprocal of the particle size. The essences of effect of particle size on adsorption thermodynamics are that lnKθ and ΔadsGmθ are influenced by both the molar surface area and the difference in surface tensions after adsorption, ΔadsHmθ by the molar surface area, the differences in surface tensions and in temperature coefficients of surface tensions, ΔadsSmθ by the molar surface area and the difference in temperature coefficients of the surface tensions.

Solid Film Formation at the Tetradecane/Aqueous Hexadecyltrimethylammonium Bromide Solution Interface Studied by Interfacial Tensiometry and X-ray Reflectometry.

The effect of oil on condensed film formation in the adsorbed film of hexadecyltrimethylammonium bromide (C16TAB) at the tetradecane (C14)/water (W) interface was examined by interfacial tension and X-ray reflectivity measurements. The interfacial tension vs temperature curves have break point due to the expanded?condensed phase transition of the adsorbed film. The partial molar entropy of C16TAB at the interface changes discontinuously, whereas the interfacial density changes almost continuously at the phase transition point. The electron density profile normal to the interface manifested that the condensed film is regarded as a two-dimensional (2D) solid rotator phase in which C16TAB and C14 molecules are densely packed with perpendicular orientation. Combining the interfacial tension and X-ray reflectivity data, the mixing ratio of C16TAB to C14 in the solid film was determined to be 2:3 and thus the film is enriched in oil molecules than surfactant ones. Furthermore, the partial molar entropy change of C14 associated with solid film formation was found to be largely negative and very close to that of surface freezing of liquid alkane, manifesting that C14 molecules are well ordered to form a 2D solid film by mixing with C16TAB molecules at the interface. The solid film formation of the present system is driven by effective vdW interactions between adsorbed C16TAB and intercalated C14 molecules. The morphology of the condensed domain observed during phase transition suggested that the contact energy is more predominant than the dipole repulsion at the domain boundary, which promotes coalescence of small domains into large ones during phase transition.

Temperature effect on the distribution of lanthanides(III) in the perchlorate-malonamide-methyl isobutyl ketone systems

Distribution ratios of trivalent lanthanide ions in extraction reactions may be affected by the denticity of a solvent extraction ligand for entropic reasons. This hypothesis was tested by studying the reactions of extraction of the lanthanides(III) (La, Nd, Eu, Dy, Er and Yb) from perchlorate media into methyl isobutyl ketone (MIBK) with three structurally related malonamide ligands (I – III): 2,2′-[1,2-phenylenebis(methylene)]bis(N,N,N’,N’-tetrabutylmalonamide) (I), 2,2′-[1,4-phenylenebis(methylene)]bis(N,N,N’,N’-tetrabutylmalonamide) (II), and 2-benzyl-N,N,N’,N’-tetrabutylmalonamide (III), the molecules of which contain either two (III) or four (I and II) carbonyl oxygen donor atoms. Ligands I and II are the structural isomers. The extracted species in the reactions with all these ligands have the (1:2) metal-to-ligand stoichiometric ratios. All the extraction reactions are enthalpy-driven and have negative values of the standard molar entropy changes at T = (298–313) K. Since the least exothermic standard molar enthalpy changes of the extraction reactions (ΔrH°T) and the least negative standard molar entropy changes of the reactions (ΔrS°T) were observed for ligand I, it was concluded, that the distribution ratios of the lanthanide(III) ions were the highest in the reactions with I due to the entropic effect, presumably resulting from the difference in the coordination of the extraction ligands with the lanthanide(III) ions.

Measurement and modelling of solubility data for bosentan in 1-propanol + water mixtures at various temperatures

ABSTRACTThe experimental solubility determination of bosentan (BST) in 1-propanol + water mixtures within temperature range, T = (293.15–313.15) K were performed by applying the shake-flask method. The solubility data were correlated by four cosolvency models, which are the Jouyban-Acree, Jouyban-Acree-van’t Hoff, modified Wilson, and Yalkowsky equations. The back-calculated solubility using the Jouyban-Acree-van’t Hoff equation presents better compatibility with the experimental data than those by the other models. Thermodynamic properties such as apparent molar enthalpy, entropy, and Gibbs free energy change of BST dissolution process in the binary (1-propanol + water) mixtures were also calculated which indicative of the inspontaneous process of dissolution.

INFLUENCE OF PRESSURE ON EXCESS THERMODYNAMIC CHARACTERISTICS OF WATER + ETHYLENEDIAMINE MIXTURE

The variations of excessmolarthermodynamic characteristics: Gibbs energyΔP0→PGmE, entropy ΔP0→PSmE and enthalpy ΔP0→PHmE forthe mixture of water +ethylenediamine in the temperature range of 288.15-323.15K and pressures increase up to 100 MPa were calculated. Concentration dependences ofΔP0→PGmE, ΔP0→PSmE иΔP0→PHmE versus mole fractionof ethylenediamine (x2) at all values ofpressure studied were characterized by the presenceof maxima. A correlation of the mixture melting diagramand change in excess molar entropy from concentration (D Po→pSmE=f(x2))was found.

Adsorption and thermodynamic studies of pure and binary CO2 and N2 gas components on nitrogen enriched nanostructured carbon adsorbents

Abstract Adsorption isotherms of pure components (CO2 and N2) on nitrogen enriched nanostructured carbon (UFZ-700) were evaluated at four different adsorption temperatures ranging from 303 to 373 K using a static volumetric analyzer. They were then correlated with the three pure component adsorption isotherm models namely Langmuir, Sips, and dual-site Langmuir (DSL) models. Binary components (CO2-N2) adsorption equilibria were then predicted by extending Sips and DSL equations empirically along with usage of ideal adsorbed solution theory. Further, it was compared with experimental data obtained from the breakthrough curves by various phase diagrams. Binary system breakthrough data were obtained at four different CO2 feed concentration and four adsorption temperatures (303–373 K) using a fixed-bed column. Sips and DSL adsorption isotherm models fitted well among three pure component adsorption isotherm models indicating energetically heterogeneous adsorbent surface. Because of the difference in adsorptive strengths of CO2 and N2 molecules, the models extended forms highly under-predicted the amount of CO2 adsorbed over the whole temperature and feed concentration range. Also, ideal adsorbed solution theory failed to describe the mixed-gas adsorption equilibria. With the increase in CO2 gas phase molar fraction, total adsorbed amounts were found to increase, deviation indicating positive from Raoult’s law with asymmetric x-y diagrams. Thermodynamic functions such as molar Gibbs free energy change, entropy change, and enthalpy change for the pure component system were numerically evaluated. They indicated the formation of more ordered configuration of CO2 molecules on the adsorbent surface and confirmed the feasibility of adsorption process.

P21/c-C2/c phase transition and mixing properties of the (Li,Na)FeGe2O6 solid solution: A calorimetric and thermodynamic study

Abstract A calorimetric and thermodynamic study of the (Li1-xNax)FeGe2O6 solid solution with the pyroxene structure was undertaken. The molar heat capacity at constant pressure (Cp,m) for compositions with x = (0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) was measured using a Physical Properties Measurement System at temperatures from 2 K to 300 K and by differential scanning calorimetry between 282 and 870 K (these measurements were performed upon heating as well as upon cooling). Magnetic transitions below 20 K and structural P21/c ↔ C2/c phase transitions at higher temperatures were observed that decrease in temperature with increasing Na/(Na + Li). The P21/c ↔ C2/c transition showed a considerable temperature hysteresis that is largest for LiFeGe2O6 (∼30 K) and decreases with increasing Na/(Na + Li) in the pyroxene. The molar enthalpy and entropy changes associated with the P21/c ↔ C2/c phase transitions, ΔHtr,m and ΔStr,m, were determined. They can be described by quadratic and linear functions across the solid solution. A linear correlation between ΔHtr,m and the square of the volume strain at the transition temperature was established. The P21/c ↔ C2/c phase transition of LiFeGe2O6 is compared to that of α-β quartz, whose Cp,m was also measured. The molar enthalpy of order, ΔHord,m, was calculated from the calorimetric data. It has a maximum of ΔHord,m = (−11.6 ± 1.5)kJ·mol−1 for the P21/c ↔ C2/c phase transition of LiFeGe2O6, which is in reasonable agreement with a maximum ΔHord,m = −9.9 kJ·mol−1 calculated using density functional theory. ΔHord,m vs. T behavior was described using a tricritical Landau model with an a parameter of a = (41.8 ± 1.0)J·K−1·mol−1. All properties associated with the P21/c ↔ C2/c phase transition in LiFeGe2O6 can be calculated using this value. The Cp,m behavior at T 0.4 have the P21/c ↔ C2/c phase transition below 298.15 K, this results in a discontinuity in Scal,m298.15 behavior as function of composition at Na/(Na + Li) = 0.5. DQF was applied to model this behavior and the corresponding parameters were retrieved. The entropy of mixing behavior of the (Li,Na)FeGe2O6 solid solution at 298.15 K is characterized by positive excess molar magnetic entropies of mixing onto which entropy changes due to the structural P21/c ↔ C2/c phase transitions are superimposed in the Na-rich part of the binary system. Excess volumes of mixing for the (Li,Na)FeGe2O6 solid solution were calculated from published data and DQF parameters were derived that allow volume as function of temperature and composition to be calculated. The molar third law entropies at T = 298.15 K are Som = (188.3 ± 2)J·K−1·mol−1 and Som = (203.1 ± 2)J·K−1·mol−1 and the molar enthalpies of formation from the elements at T = 298.15 K are ΔfHom = (−1817.2 ± 9)kJ·mol−1 and ΔfHom = (−1834.0 ± 9)kJ·mol−1 for the end members LiFeGe2O6 and NaFeGe2O6, respectively. ΔfHom was calculated using density functional theory (DFT). Values for ΔfHom, Som, and molar volume, for the coefficients of Cp,m polynomials, for thermal expansion and for the bulk modulus of the end members were compiled and can be used, in combination with the derived volumetric and entropic mixing properties, for phase diagram calculations involving the (Li,Na)FeGe2O6 solid solution.

Statistical mechanical modeling of the transition Stage II → Stage I of Li-ion storage in graphite. A priori vs induced heterogeneity

An improved model to analyze the partial molar entropy step between stage II and stage I for lithium intercalation in graphite, based in statistical mechanics, is presented. At difference with our previous formulation, which assumed a priori heterogeneities, the present model considers the more realistic case of induced heterogeneities. The present work shows that, similarly to considerations made in the literature with intercalation cathode materials, most of the partial molar entropy changes for Li insertion into graphite may be explained on a configurational basis.The interaction between ions intercalated in a same layer of graphite can be inferred to be strongly attractive, as was assumed in the literature for the simulation of voltammetric profiles.

The influence of point defects on the entropy profiles of Lithium Ion Battery cathodes: a lattice-gas Monte Carlo study

In-situ diagnostic tools have become established to as a means to understanding the aging processes that occur during charge/discharge cycles in Li-ion batteries (LIBs). One electrochemical thermodynamic technique that can be applied to this problem is known as entropy profiling. Entropy profiles are obtained by monitoring the variation in the open circuit potential as a function of temperature. The peaks in these profiles are related to phase transitions, such as order/disorder transitions, in the lattice. In battery aging studies of cathode materials, the peaks become suppressed but the mechanism by which this occurs is currently poorly understood. One suggested mechanism is the formation of point defects. Intentional modifications of LIB electrodes may also lead to the introduction of point defects. To gain quantitative understanding of the entropy profile changes that could be caused by point defects, we have performed Monte Carlo simulations on lattices of variable defect content. As a model cathode, we have chosen manganese spinel, which has a well-described order-disorder transition when it is half filled with Li. We assume, in the case of trivalent defect substitution (M=Cr,Co) that each defect M permanently pins one Li atom. This assumption is supported by Density Functional Theory (DFT) calculations. Assuming that the distribution of the pinned Li sites is completely random, we observe the same trend in the change in partial molar entropy with defect content as observed in experiment: the peak amplitudes become increasing suppressed as the defect fraction is increased. We also examine changes in the configurational entropy itself, rather than the entropy change, as a function of the defect fraction and analyse these results with respect to the ones expected for an ideal solid solution. We discuss the implications of the quantitative differences between some of the results obtained from the model and the experimentally observed ones.

Determination and correlation of solubility of linezolid form II in different pure and binary solvents

The solubility data of linezolid form II in five pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol) and a binary (water + methanol) solvent were determined among the temperature range from 283.15 K to 318.15 K under atmospheric pressure. The results indicated that the solubility increased with the temperature increasing. Seven thermodynamic models were used here to correlate the experimental solubility data. Through the comparison of the experimental data in pure solvents with the calculated results, we found that the modified Apelblat equation fit the experimental data best. Furthermore, the density functional theory (DFT) calculations showed that the solubility in different solvents related to the interaction strength between the linezolid and the solvent molecules. Finally, the molar enthalpy change, molar entropy change and molar Gibbs free energy change of dissolution of linezolid in the different solvents were also calculated by van't Hoff equation in this paper.

Correlation and prediction of the solubility of the racemic tartaric acid–ethanol–water system with the NRTL model

The solubility data on solid–liquid equilibria (SLE) of racemic tartaric acid in ethanol+water mixtures were measured in the temperature range of (293.15 to 318.15) K at 0.1MPa by acid–base titration method. In the binary solvent mixtures the solubility of racemic tartaric acid increases with rising temperature and decreases with increasing ethanol content. The modified Apelblat equation, λh equation and CNIBS/R–K equations were applied to describe and predict the change tendency of solubility. Computational results show that the modified Apelblat equation is superior to the others. Furthermore, a predictive version of the NRTL model was proposed for the description of the non-ideality of the racemic tartaric acid–ethanol–water system. The predicted values were compared with the experimental data. The agreements are good. By using the van't Hoff equation the molar enthalpy, entropy and Gibbs free energy changes of solution were calculated. A linear ∆solH versus ∆solS compensation plot with a positive slope was obtained by means of enthalpy–entropy compensation effect.