Positive Excess Volumes Research Articles

Molecular interactions in ethyl caprate and 2-alcohol: Extended hard sphere framework

BackgroundThe study investigates the liquid densities and viscosities of Ethyl caprate (EC) combined with various 2-alkanols across a temperature spectrum of 293.15 to 323.15 K, aiming to understand the intermolecular interactions and deviations from ideal behavior. MethodsExperimental density and viscosity for the mixtures were measured with the SVM Stabinger viscometer. A modified rough hard-sphere theory was employed to model the viscosity of pure substances and binary liquids, incorporating temperature-dependent parameters. Significant Findings: All examined mixtures exhibited positive excess molar volumes. The modified rough hard-sphere model demonstrated a maximum viscosity error of 4.12 % for 2-hexanol in the temperature range of 293 to 323 K. For binary mixtures, the calculated values closely matched experimental data, with a maximum deviation of 3.51 % observed for the EC + 2-butanol mixture, highlighting the model's predictive accuracy.

Exploring the thermodynamic properties of 2-Methyl-1-butanol and C7-C10 alcohols through CPA modeling and experimental analysis

This paper presents an investigation into the thermodynamic and transport characteristics of 2-methyl-1-butanol and C7-C10 normal alcohols (1-heptanol to 1-decanol), with a specific focus on their binary mixtures. The experimental analysis encompassed a temperature range of 293.15 to 323.15 K, during which the density and viscosity of these mixtures were measured. The study reveals that all the binary mixtures exhibit positive excess molar volumes, which progressively increase as the alkyl chain length in the alcohols increases. Simultaneously, the observed viscosity deviations consistently display negative values across all the mixtures, becoming more pronounced as the alkyl chain lengthens. This behavior of the mixtures highlights the weak molecular interactions between 2-methyl-1-butanol and alcohols. In conjunction with the experimental work, this study utilizes the Cubic-Plus-Association (CPA) model to establish a correlation between the densities of these binary mixtures. The model demonstrates a satisfactory agreement with the experimental densities, signifying its efficacy in correlating the density behavior of such mixtures. The largest discrepancy between the experimental data and the correlated values from the CPA model was observed in the mixture of 2-methyl-1-butanol with 1-heptanol, amounting to a mere 0.29 %. This minor deviation underscores the correlation of the CPA model in reproducing experimental results.

Integrated exploration of intermolecular interactions in 3-methyl-1-butanol and C5-C8 1-alkanol mixtures via density functional theory and experimental approaches

The investigation provides a study on the thermophysical properties of 3-methyl-1-butanol with medium-chain alcohols (1-pentanol to 1-octanol) within the temperatures 293.15 K to 333.15 K. Findings indicate positive excess molar volumes that escalate with the lengthening of the carbon chain in the alcohols. Viscosity measurements demonstrate negative deviations from ideality, which are accentuated with longer alkyl chains. The analysis suggests that intermolecular forces between 3-methyl-1-butanol and alcohols are weak. Furthermore, the study uses the Cubic Plus Association (CPA) model to establish a relationship between the densities of the mixtures, demonstrating a close match with data obtained through experimentation. The CPA model deviates by a maximum of 0.53 % and indicates the model's reliability in portraying real-world data. Furthermore, this study entails a density functional theory (DFT) investigation of hydrogen bonding among 3-methyl-1-buthanol + 1-alkanol. The analysis encompasses properties including interaction energies, geometrical parameters, nuclear magnetic resonance (NMR) analyses, atoms in molecules analysis (AIM), natural bond orbital analysis (NBO), and excess volume. Our calculations reveal the strongest hydrogen bonding occurs in mixtures of 3-methyl-1-butanol and 1-pentanol, while the weakest interactions form in mixtures of 3-methyl-1-butanol and 1-octanol. Notably, calculated data on hydrogen bonding between 3-methyl-1-buthanol and 1-alkanols align with experimental findings, underscoring the agreement between computational and empirical approaches.

Clarification of origin of positive excess volume of Pd–Fe binary alloys by using first-principles calculations and HAXPES

Disordered Pd–Fe alloys show a positive excess-volume effect, contrary to the predictions of the Iida–Guthrie model. The effect becomes larger at a composition of approximately Pd0.5Fe0.5. The origin of the positive excess-volume effect was investigated by using first-principles calculations to study the electronic structures in the ordered and disordered states of Pd–Fe alloys with two different compositions, i.e., Pd0.53Fe0.47 and Pd0.75Fe0.25. The calculated partial density of states for the disordered state in Pd0.53Fe0.47 indicates weakening of Pd metallic bonds because of fully occupied 4d majority-spin states with enhanced anti-bonding characteristics, which cause an increase in the volume. In addition, the magneto-volume effect, which minimizes the increase in the electronic kinetic energy caused by exchange splitting, contributes to the positive excess volume. The calculated electronic states and those obtained from hard X-ray photoelectron spectra were consistent with each other.

Experimental and in silico insights: interaction of dimethyl sulphoxide with 1-hexyl-2-methyl imidazolium bromide/1-octyl-2-methyl imidazolium bromide at different temperatures.

Ionic liquids have gained attention as 'designer solvents' since they offer a broad spectrum of properties that can be tuned by altering the constituent ions. In this work, 1-alkyl-2-methyl imidazolium-based ionic liquids with two different alkyl chains (alkyl = hexyl and octyl) have been synthesized and characterized. Since the binary mixture of ionic liquids with molecular solvents can give rise to striking physicochemical properties, the interaction of the synthesized room temperature ionic liquids, 1-hexyl-2-methyl imidazolium bromide [HMIM][Br]/1-octyl-2-methyl imidazolium bromide [OMIM][Br] with DMSO has been examined through density and specific conductance at T = (303.15, 308.15, 313.15 and 318.15) K under atmospheric pressure. The obtained molar volume and excess molar volume are fitted to the Redlich-Kister polynomial equation, and the standard deviation is noted. The positive excess molar volume at elevated temperatures indicates volume expansion due to the mutual loss of dipolar association and differences in the sizes and shapes of the constituent molecules. To have a better understanding of the reactivity and efficacy of 1-hexyl-2-methyl imidazolium bromide and 1-octyl-2-methyl imidazolium bromide with DMSO, the Becke, 3-parameter, Lee-Yang-Parr (B3LYP) correlation function of density functional theory (DFT) has been used. The ORCA Program version 4.0 calculates the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy. The effective reactivities of both the compounds that showed an energy band gap (ΔE), i.e., the difference between ELUMO and EHOMO, are 7.147 and 8.037 kcal mol-1.

Volumetric Behaviour of Binary Mixture of Dual Purpose Kerosene (DPK) and Automotive Gas Oil (AGO) at 303K

The study of volume changes in binary mixtures is attracting considerable interest from researchers due to the degree of molecular interaction between the mixed solvent molecules and their importance in many chemical industries and engineering disciplines. The experimental values of densities (ρ) and viscosities (η) of pure and binary mixtures of dual-purpose kerosene (DPK) and automotive gas oil (AGO) were obtained over the whole range of mixture composition at a temperature of 303 K. The experimental data obtained were employed to determine the excess molar volume (V_m^E), excess viscosity (VE), and excess Gibb’s free energy of activation (ΔGE) based on the molecular interactions arising due to the structural effect of the mixture. The measured viscosity values were correlated with Grunberg and Nissan, Kendel and Monroe, and Frenkel’s semi-empirical models to evaluate the best fit for the system. The results acquired were explained according to their structural differences, strength, and nature of intermolecular interactions in the binary mixture. The experimental result revealed that the binary mixture of DPK and AGO shows positive excess molar volume and negative excess viscosity. Weak, specific interactions were responsible for the dispersion force in the binary mixtures.

A revised model for activity–composition relations in solid and molten FePt alloys and a preliminary model for characterization of oxygen fugacity in high-pressure experiments

Abstract. We present new models for the activity of iron (γFe) in solid face-centered cubic (fcc) and liquid FePt alloy at high temperature and pressure to facilitate their use as sliding buffer redox sensors under extreme conditions. Numerous experimental studies of γFe in FePt alloy at 100 kPa have produced a wide spread of values. By favoring high-temperature studies that are more likely to have produced equilibrium measurement and excluding experiments for compositions and temperatures that probably encountered ordered or unmixed low-temperature phases, we regress an asymmetric Margules activity–composition model with parameters WFePtfcc=-121.5±2.1 kJ mol−1 and WPtFefcc=-93.3±4.3 kJ mol−1. These values are close to the widely used model of Kessel et al. (2001), but for Pt-rich compositions they predict larger Fe activities and correspondingly more reduced oxygen fugacities. Activity–composition relations in liquid FePt are calibrated from direct measurements of activities and, most sensitively, from the trace of the Fe–Pt liquidus. Together, these yield asymmetric Margules parameters of WFePtliq=-124.5 kJ mol−1 and WPtFeliq=-94.0 kJ mol−1. The effects of pressure on both fcc and liquid FePt alloy are considered from excess-volume relations. Both solid and liquid alloy display significant positive excess volumes of mixing. Extraction of the excess volume of mixing for fcc FePt alloy requires filtering data for ordered low-temperature phases and corrections for the effects of magnetostriction on Fe-rich compositions which exhibit “Invar” behavior. Applied at high temperatures and pressures, both solid and liquid FePt alloys have strongly negative deviations from ideality at low pressure, which become closer to ideal at high pressure. These models provide a provisional basis for the calculation of aFe in high-temperature, high-pressure experiments that, when combined with estimates of aFeO, allow characterization of fO2 under conditions relevant to magma oceans, core formation, and differentiation processes in the lower mantle of Earth or on other terrestrial planets. Improvements in these models require new constraints on the equation of state of FePt fcc alloy and documentation of the high-pressure melting relations in the system Fe–Pt.

Density, Excess Molar Volume and Vapor–Liquid Equilibrium Measurements at 101.3 kPa for Binary Mixtures Containing Ethyl Acetate and a Branched Alkane: Experimental Data and Modeling

Vapor–liquid equilibrium (VLE) and density data for binary systems of branched alkanes + ethyl acetate are scarce in the literature. In this study, the binary mixtures 3-methylpentane + ethyl acetate and 2,3-dimethylbutane + ethyl acetate were investigated. Density measurements at atmospheric pressure were performed using a vibrating tube density meter at 293.15, 298.15 and 303.15 K. Large and positive excess molar volumes were calculated and correlated using a Redlich–Kister-type equation. Isobaric VLE data at 101.3 kPa were obtained using a Gillespie-type recirculation ebulliometer. Equilibrium compositions were determined indirectly from density measurements. The experimental data were checked for consistency by means of the Fredenslund test and the Wisniak (L-W) test and were then successfully correlated using the NRTL model. The newly studied binary systems display high deviations from ideality and minimum boiling azeotropes, the coordinates of which are reported in this work.

Relationship of the atomic dynamics and excess volume of a copper rich Cu76Ti24 alloy melt

We investigate the atomic dynamics of a Cu-rich Cu76Ti24 alloy between 1223 K and 1453 K using the quasi-elastic neutron scattering technique. The obtained mean Cu/Ti self-diffusion coefficient D exhibits an Arrhenius-like temperature dependence with an activation energy of 0.46�0.02 eV per atom. Compared with those of the pure elements at a given temperature, D is slower than that for pure Cu, but similar to pure Ti. This slowing down of the liquid dynamics upon alloying has been observed for most binary alloy systems. However, in this study, the packing fraction of the Cu-Ti alloy is lower than that of the pure elements, which can be explained by the positive excess volume of the Cu-Ti system. Therefore, the compositional dependence of the atomic dynamics cannot be linked to a macroscopic packing argument. Only, the atomic dynamics is not correlated with an increase of the average packing fraction of the melt.

Difference in aqueous solution structure at 293.2 and 473.2 K between ethanol and ethylene glycol via molecular dynamics

Our recent experimental study found that ethylene glycol–water mixture at 473.2 K and 10 MPa has a positive excess molar volume in water-rich region in contrast to the negative one at 293.2 K and 0.1 MPa and that in ethanol–water mixture [1]. The present study performed molecular dynamics simulation to clarify the difference in the solution structure between the two aqueous mixtures at the two temperatures. Radial distribution functions, coordination (hydration) numbers, numbers of hydrogen bonding and spatial distribution functions were calculated around the hydroxyl groups of alcohol and water molecules. In both mixtures, hydrogen bonds between alcohol and water molecules and between water molecules were shown to remain even at 473.2 K although the number of hydrogen bond decreased upon the temperature increase. In addition, at the high temperatures, it was indicated that tetrahedral-like hydrogen bonding network among water molecules was lost in ethylene glycol–water mixture whereas it remained in ethanol–water one.

Investigation of physicochemical properties of NADES based on choline chloride and ascorbic acid and its binary solutions with DMSO from (298.15 to 353.15) K

There is growing environmental concern created by large scale use of organic solvents. The quest to replace them with benign solvents led to the synthesis of ionic liquids (ILs) and later deep eutectic solvents (DES) as green replacements for volatile organic compounds. Although ILs and DES have similar physicochemical properties, DES are preferred because their toxicity is low compared to ILs and because they are easily synthesized from inexpensive and readily available precursors. Among DES, natural deep eutectic solvents (NADES) are gaining more attention due to their several naturally abundant precursors. Due to higher benefits of NADES, it is desirable to explore their physicochemical properties. The present study investigates the physicochemical properties of ChCl/AA NADES and its mixtures with dimethyl sulfoxide (DMSO). The effect of composition and temperature in the range (298.15–353.15) K on these properties is also investigated. The ChCl/AA NADES and DMSO mixtures demonstrate positive excess molar volume, with maximum centered close to x1=0.7 (x1 is mole fraction of ChCl/AA NADES) which became more prominent with increasing temperature. In contrast, a relatively broad minimum is observed for excess molar viscosity and the obtained information is further used to explain the molecular interactions in the NADES - DMSO system. The temperature dependence of viscosity and electrical conductivity is explained satisfactorily using Vogel-Fulcher- Tammann (VFT) equation.

Molar Volume and Surface Tension of Liquid Bi\u2013Cu Alloys

Bi–Cu alloys may potentially be used for thermal energy storage or as a catalyst for methane pyrolysis. For application research and simulations, it is necessary to know the reliable thermophysical properties of liquid alloys. Density of liquid Bi–Cu alloys (25, 50, 75 at. pct Cu) was measured with dilatometric method over the 971 K to 1500 K range. Density decreases linearly with temperature for all compositions. The molar volume calculated from measured densities shows positive excess molar volume. Surface tension was measured with maximum bubble pressure method over the 1125 K to 1500 K range. The data fitted with linear equations show that while the surface tension of 25 at. pct Cu decreases and that of 50 at. pct Cu alloy does not vary with temperature, the surface tension of 75 at. pct Cu alloy increases with temperature. The present results are confronted with literature data and several model calculations, part of which were performed in Pandat, and the reasons for positive excess molar volume and surface tension temperature coefficient are explained in terms of thermodynamics of Bi–Cu solutions.

Density and excess volume of liquid copper, nickel, iron, and their binary alloys

Abstract The densities of liquid copper, nickel and iron and their binary alloys have been measured over a wide temperature range, including the undercooled regime. A non-contact technique was used, consisting of electromagnetic levitation and optical dilatometry. In all cases the density was a linear function of temperature. On the other hand, the concentration dependence was only linear for Fe –Ni, whereas Fe –Cu and Cu–Ni are characterized by a positive or negative excess volume respectively.

Association effect on the density, viscosity and excess properties of fatty acid ester + alcohol mixtures: Experiment and modeling

The mixtures of fatty acid ester + alcohol are promising substitution fuels in engines. Due to their strong self- and cross-hydrogen bonds, the properties of these kinds of mixtures may show different characteristics from the fossil fuels composed of non-associating substances. In this work, the association effects on density and viscosity of fatty acid ester + alcohol are investigated from both experimental and theoretical aspects. The ethyl laurate + ethanol mixtures with 9 M fraction compositions are chosen, and the two properties are measured using a capillary viscometer system at temperatures from 313 K to 343 K and pressures up to 15 MPa. The positive excess volume and viscosity deviation of the mixtures are obtained, and the former is negligible compared to the experimental uncertainty. The Cubic-Plus-Association equation of state (CPA EoS) and the friction theory model are used to model the mixtures of ethyl laurate + ethanol. The relations of their self- and cross-associations to density, viscosity, and two excess properties (excess volume and viscosity deviation) are summarized. Different saturated fatty acid ester + 1-alcohol mixtures are also modeled with the CPA EoS. The variation characteristics of their viscosity deviations are analyzed and explained by their different association strength and the mole number of associated molecules.

The solid state of anti-inflammatory morniflumate diniflumate: A cocrystalline salt

Morniflumate diniflumate, a molecular compound involving niflumic acid and its β-morpholino ethyl ester (morniflumate) in the mole ratio 2:1, is found to crystallize in a triclinic P − 1 space group with a unit-cell volume of 2203.4(5) Å3. It is a cocrystal between a morniflumate+ niflumate− salt and a neutral niflumic acid molecule. The co-crystalline salt forms endothermically with a positive excess volume and it melts incongruently at 382.3(8) K. Differential scanning calorimetry executed at heating rates above 20 K⋅min−1, leads to congruent melting at 387.8(9)K with an enthalpy change of ΔfusH = 80(2) J g−1. The rare occurrence that incongruent and congruent melting can be observed for the same cocrystal may be due to the conformational versatility of the niflumic acid molecule and its slow conversion between the different conformations due to weak intramolecular hydrogen bonding.

Effect of phosphorus P-π bonding on the volumetric properties and vapor-liquid equilibrium of phosphorus trichloride-benzene liquid mixtures

New density and vapor–liquid equilibrium data of PCl3-benzene binary system at atmospheric pressure (99.7–101.3 kPa) were carefully measured to provide crucial information for their industrial reaction and separation. The experimental mixture densities show excellent linear dependence on both solution composition and temperature and a generalized empirical correlation is proposed with an average relative deviation of 0.13%. The specific attractive P-π interaction between the phosphorus atom of PCl3 and the π cloud of benzene seems to be quite strong in solution, leading to large negative excess volumes. But the π-π antibonding effect from benzene dimers are predominant in PCl3 highly dilute solution, where positive excess volume and excess partial molar volumes of PCl3 were observed. Experimental bubble points of the binary mixture were corrected to those under 101.325 kPa. Two distinctive methods of coexistence equation and activity coefficient models of Wilson and NRTL equations were applied to model the VLE data, and they yielded very consistent results. Although no azeotrope were found, this mixture exhibited quite low relative volatility.

Phase equilibria and thermophysical properties of aqueous solutions of two bis(fluorosulfonyl)imide-based ionic liquids

Ionic liquids comprising bis(fluorosulfonyl)imide (FSI) anion have been recognized to be well suited for technological applications as solvent and electrolyte media. In this work, we thoroughly investigated the thermodynamic and transport behavior of binary aqueous systems of two hydrophobic FSI-based ionic liquids, namely [EMIM][FSI] and [BMPYR][FSI]. Systematic measurements of phase equilibria, density, viscosity, and electric conductivity were conducted, our aim being to provide truly reliable information that would substantially upgrade that existing in the literature. Employing DSC measurements on the neat ILs and dynamic measurements of freezing or cloud point temperatures as well as static solubility measurements for aqueous ILs, phase diagrams for both these systems over a 100 K window were established. Rather large solubilities of water in these ILs allow for measurements of various other properties in the homogeneous IL-rich region. Extensive data thus obtained on water activity in this region were correlated for each system simultaneously with the mutual liquid-liquid solubilities, using an extended SSF (Sum of Symmetrical Functions) equation. This global excess Gibbs energy model not only accurately captures all the VLE, LLE, and SLE data we determined experimentally, but also discloses an enthalpy-driven system energetics with hydrophobic hydration effects that are more pronounced in the case of [BMPYR][FSI]. The measurements of density, viscosity, and conductivity covering the systems from the neat ILs to those almost saturated with water gave positive excess volumes and negative viscosity deviations that rise and diminish, respectively, as T increases. The conductivity increases monotonously with increasing water content and temperature. Accurate functional representations were also established for the volumetric, viscosity, and conductivity data, capturing simultaneously their composition and temperature dependence. The linkage between conductivity and viscosity was further analyzed by means of the fractional Walden rule which provided excellent fits for both isopleths and isotherms and indicated comparatively weaker coupling for the [BMPYR][FSI] system and the direction of the isothermal composition changes. Finally, comparing the FSI ILs with their TFSI analogs, the former were found to be clearly less hydrophobic.

Stock market reactions to social media: Evidence from WeChat recommendations

This paper examines the market behavior of stocks that are favorably mentioned on official WeChat account (OWA). To the best of our knowledge, we are the first to investigate market reactions to recommendations on WeChat. The empirical results show that there is a significantly positive abnormal return and excess trading volume on the publication day. Moreover, the cumulative average abnormal return for OWA completely reverses in a short time, which supports the price pressure hypothesis. Additional analyses reveal that market reactions in the smaller firms are significantly greater than those in the largest firms on the publication day. Finally, we preclude possibilities that market reactions on the event day are induced by the secondary dissemination of analyst recommendations, firm-specific news releases, media coverage, and previous positive significant abnormal returns.

Do Mutual Funds Flows Lead to Fire-sales and Pose Systemic Risk?

Assessing systemic risk of mutual funds as a result of liquidity transformation is difficult because the frequency of flow and holdings data available is too low to properly isolate the price impact of redemption-driven sales of portfolio assets. Exchange-traded funds (ETFs) offer the advantage of daily observations of redemptions as well as the exact assets which might be sold in the underlying market. Exploiting this advantage, we show for extreme redemptions from individual corporate bond ETFs during normal times and stressed markets as well as for the largest aggregate redemptions from all corporate bond ETFs that the concern of systemic risk is not supported by the data. For the most extreme daily redemptions between 2009 and 2017, we find that for many bonds received in-kind for ETF shares, customer sell volumes in excess of average past daily customer sell volumes are either negative or large multiples of the maximum potential redemption implied sale of bonds. Further, we show that among the bonds with positive excess customer sell volumes, the extreme redemption implied sale of bonds relative to the standard deviations of past daily customer sell volumes was large for only very few of them. Corroborating the results, using regression analyses we find no evidence that extreme redemption implied sales of bonds led to abnormal negative price impacts in the underlying bond market. These findings imply that extreme redemption implied asset sales in the corporate bond market have not triggered wide-spread fire sales.

Selection and characterization of non-ideal ionic liquids mixtures to be used in CO2 capture

Due to the costs involved, the capture of CO2 in post-combustion is not currently seen as economically viable. Aiming at changing the perception of post-combustion CO2 from a costly and non-profitable process to a valuable commodity and fostering the development of the next-generation of technologies, novel solvents and their mixtures have been investigated. In this work, mixtures of non-volatile ionic liquids were screened by COSMO-RS aiming to find mixtures with positive excess volumes that could present an increased CO2 capture by physical sorption. The most promising mixtures identified by COSMO-RS, [C4C1im][DMP] or [C4C1im][NTf2] + carboxylate-based protic ILs were characterized through the measurement of their thermophysical properties, namely density and viscosity. Both properties were measured for pure ILs and their binary mixtures at different temperatures and compositions. The temperature dependence of density of pure ILs was described using the Gardas and Coutinho model while viscosity was accurately described using the Vogel−Tammann−Fulcher equation. The Redlich-Kister equation was used to predict the excess molar volumes and the non-ideality of the mixtures’ viscosity was assessed using the Grunberg and Nissan mixing law. The excess molar volumes for mixtures containing [C4C1im][DMP] show large positive values all over the range of compositions and temperatures, making them good candidates for CO2 capture. To the best of our knowledge, the excess molar volumes obtained in this work were the highest reported so far. COSMO-RS was able to correctly predict the trend of the experimental excess molar volumes for these mixtures. Regarding viscosity, mixtures of [C4C1im][DMP] with the carboxylate-based protic ILs led to the desired viscosity decrease compared to the pure aprotic IL, and large deviations from ideality were observed. The mixing of ILs is thus an efficient way to fine-tune the properties, in this case decreasing the viscosity while increasing the sorption capacity.