Entropy Of Formation Research Articles

Термодинамічні властивості і фазові рівноваги в сплавах системи Al—Се

The thermochemical properties of melts of the Al—Ce system at temperatures of (1380—1490)  3 K in range of compositions 0 < xAl < 0,38 were determined by the method of isoperibolic calorimetry. It was established that the minimum value of the enthalpy of mixing of these melts is −40,9  4.1 kJ/mol and corresponds to the melt with xAl = 0,67, and =−83,3 ± 4,8; = −200 ± 26,0 kJ/mol. Using our own and literature thermochemical data for melts and intermediate phases of the Al—Ce system, as well as its diagram state according to the ideal associated solution (IAS) model, all thermodynamic properties of melts and associates in melts and intermetallics were calculated and optimized. It was established that the calculated activities of the components in the melts of this system show large negative deviations from ideal solutions. which correlates with their thermochemical properties. The maximum mole fraction of associates CeAl2, CeAl reaches values of 0,4 and 0,24, and the other three (Ce2Al, CeAl3, CeAl5) — 0,16; 0,08, and 0,11, respectively. The minimum values of Gibbs energies and entropies of melt formation are equal to -28,2 kJ/mol and -7,6 J/mol∙K. The temperature-concentration dependences of Gibbs energies, enthalpies and entropies of melt formation and temperature for intermetallics were also calculated using the IAS model, and from them, the liquidus curve of the phase diagram of this system. As a result, complete information on the thermodynamic properties of all phases and the liquidus curve of the phase diagram of the Al—Ce system was obtained. In order to confirm the reliability of the obtained data and search for general regularities of the thermodynamic characteristics of alloying of the Al—Ce system, it was considered as a member of the series of Al—Ln(Ln-lanthanide) systems. For this, the enthalpies of formation were analyzed. intermetallics LnAl2, as well as the minimum values of thermochemical properties of melts, relative differences in molar radii and differences in electronegativities of the components of the Al—Ln systems and their dependence on the lanthanide serial number. It is shown that all dependences, except for the electronegativity differences of the components, are compatible with each other. This indicates that the thermodynamic properties of compounds and melts of Al—Ln systems are determined by the size factor. Keywords:: method calorimetry, mixing enthalpy, activity, aluminum, cerium, melts, intermetallics, thermodynamic properties, ideal associated solution model.

Entropy-driven formation of a self-assembled molecular capsule through release of amine from ammonium carboxylate salt

Abstract In this study, we investigated the formation of a self-assembling hetero-porphyrin capsule, stabilized through aminoquinolinium/carboxylate salt bridge interactions, in the presence of amines. The formation of the capsule, accompanied by the release of 4 amine molecules from the carboxylate salt, is driven by entropy when excess amines are present, and entropy and enthalpy of the capsule formation can be regulated with varying amounts of amine. Notably, increasing the size of the added amines enhanced the entropy.

Destinezite: physicochemical and calorimetric study

Destinezite (Fe3+ Al0.02)(PO4)0.99(SO4)0.90(OH)1.20 ⋅ 5.97H2O (Czech Republic) has been studied by thermal and electron-microprobe analyses, X-ray powder diffraction, IR, Raman, and Mössbauer spectroscopy. The enthalpy of formation of destinezite Fe3 +(PO4)(SO4)(OH)⋅6H2O from the elements ∆fH0(298.15 K) = −4258 ± 12 kJ/mol was determined by the method of solution calorimetry in melt lead borate 2PbO ⋅ B2O3 on a Calvet microcalorimeter Setaram (France). The value of its absolute entropy S0(298.15 K) = 462.0 J/(mol⋅K) was estimated, the entropy of formation ∆fS0(298.15 K) = −2054 J/(mol⋅K) and the Gibbs energy of formation from the elements ∆fG0(298.15 K) = −3646 kJ/mol.

Understanding the Role of Entropy in Promoting Electrocatalytic CO2 Reduction

A global push towards increased sustainability requires technologies that enable the long-term storage of renewable electricity and the sustainable synthesis of chemicals. The electrochemical reduction of CO2 to fuels and chemicals represents a promising avenue to meet these goals. Yet, despite extensive research, many fundamental aspects of the interfacial interactions that enable this reaction remain unclear. One simple question that has not been addressed to date is the mechanism through which the applied potential controls the rate of CO2 reduction. To provide insight, we measured CO2 reduction activation energies on Ag electrodes in the presence of different cations. Building on our earlier work (J. Am. Chem. Soc. 2016, 138, 25, 7820–7823), where some of us demonstrated the important role of structural modifications to imidazolium cations in controlling the rate of CO2 reduction reactions, we expected that these structural modifications impact the reaction rate through changes to the activation energy. However, our findings revealed a much more fascinating picture of the impact of imidazolium cations on CO2 reduction rates.By measuring the activation energy in the presence of imidazolium cations with different structural features, we find that introducing 1-ethly-3-methylimidazolium (EMIM) results in an apparent activation energy of zero. Under these conditions, the applied potential modifies the reaction rate solely through changes to the pre-exponential factor of the Arrhenius equation.Based on literature on homogeneous catalysis, we suggest that our finding indicates that the rate of CO2 reduction in the presence of EMIM is entirely controlled by the formation entropy of the CO2 reduction transition state, with the potential likely influencing the rate by modifying the degree of ordering of imidazolium cations at the electrode surface. We further show that proton abstraction from EMIM forms a neutral compound, resulting in the elimination of the rate enhancement. Our results provide important new insight into the mechanism through which the applied potential controls the rate of electrocatalytic reactions and we expect them to be of broad importance to a better understanding of the connection between interface structure and electrocatalytic rates.

Additive single atom values for thermodynamics III: Formation entropies and Gibbs energies for ionic solids – Hydrate and anhydrate data, and a correction

In the initial two publications in this series we established predictive additive Atom Sum thermochemical quantities for inorganic solids for each of the chemical elements. With the chemical elements being a finite set, these data cover the whole of the domain of inorganic solids so far as reference data is currently available.We here introduce a dataset augmented in hydrates, and divide our analysis between the hydrates and anhydrates. The Atom Sum terms are better directed independently to these disparate inorganic groups thus providing improved estimates of the corresponding predicted thermochemical quantities. In this paper we provide both updated formation reaction entropies and previously unpublished Gibbs energies.

Quantum chemical modeling of alkane 2D monolayer formation on graphene

The paper presents a quantum chemical approach for assessment of the thermodynamic parameters of association for alkanes CnH2n+2 (n = 6–14) and polyaromatic hydrocarbons (PAH) of the coronene series as model structures of the graphene surface within the framework of semiempirical methods. The enthalpy, entropy and Gibbs energy of formation and binding for alkanes with PAH were calculated using the PM3 and PM6-DH2 methods. It is shown that an adequate description of the interactions in the regarded complexes requires the use of PM6-DH2 method, since it contains corrections for dispersion interactions and hydrogen bonds. The parallel orientation of the alkane molecule relative to the coronene plane is proved to be more energetically preferable than perpendicular one, which is consistent with experimental data.Intermolecular C–H/π interactions are revealed to be crucial in the 2D film formation of alkanes on graphene/graphite. While interactions between alkane molecules make a destabilizing contribution due to the implementation of energetically unfavorable types of intermolecular CH/HC interactions. This stipulates a threshold chain length of alkanes capable of film formation on the graphene/graphite surface at standard temperature: 14 and 19 carbon atoms for parallel and perpendicular oriented alkanes, respectively. The obtained threshold values of the alkane chain length, as well as the geometric parameters of their orientation in 2D monolayers on the graphene/graphite surface are consistent with available experimental data.

Physical Analysis and Mathematical Modeling of the Hydrogen Storage Process in the MmNi4.2Mn0.8 Compound.

The results of an experimental and mathematical study into the MmNi4.2Mn0.8 compound's hydrogen storage properties are presented in the present research. Plotting and discussion of the experimental isotherms (P-C-T) for different starting temperatures (288 K, 298 K, 308 K, and 318 K) were carried out first. Then, the enthalpy and entropy of formation (ΔH0, ΔS0) were deduced from the plot of van't Hoff. Following that, the P-C-T were contrasted with a mathematical model developed via statistical physics modeling. The steric and energetic parameters, such as the number of the receiving sites (n1, n2), their densities (Nm1, Nm2), and the energy parameters (P1, P2) of the system, were calculated thanks to the excellent agreement between the numerical and experimental results. Therefore, plotting and discussing these parameters in relation to temperature preceded their application in determining the amount of hydrogen in each type of site per unit of metal ([H/M]1, [H/M]2) as well as for the entire system [H/M] versus temperature and pressure besides the absorption energies associated with each kind of site (ΔE1, ΔE2) and the thermodynamic functions (free energy, Gibbs energy, and entropy) that control the absorption reaction.

The metal-poor atmosphere of a potential sub-Neptune progenitor

Young transiting exoplanets offer a unique opportunity to characterize the atmospheres of freshly formed and evolving planets. We present the transmission spectrum of V1298 Tau b, a 23-Myr-old warm Jupiter-sized (0.91 ± 0.05 RJ, where RJ is the radius of Jupiter) planet orbiting a pre-main-sequence star. We detect a mostly clear primordial atmosphere with an exceptionally large atmospheric scale height, and a water vapour absorption at a 5σ level of significance, from which we estimate a planetary mass upper limit (23 Earth masses, 0.12 g cm−3 at a 3σ level). This is one of the lowest-density planets discovered so far. We retrieve a low atmospheric metallicity (logZ=−0.7−0.7+0.8solar\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\log{Z}=-0.{7}_{-0.7}^{+0.8}\\,{\\mathrm{solar}}$$\\end{document}), consistent with solar/sub-solar values. Our findings challenge the expected mass–metallicity relation from core-accretion theory. Our observations can instead be explained by in situ formation via pebble accretion together with ongoing evolutionary mechanisms. We do not detect methane, which hints at a hotter-than-expected interior from just the formation entropy of this planet. Our observations suggest that V1298 Tau b is likely to evolve into a sub-Neptune.

Study of the solid-phase equilibria in the GeTe-Bi2Te3-Te system and thermodynamic properties of GeTe-rich germanium bismuth tellurides

A set of self-consistent thermodynamic parameters of the GeTe-rich germanium-bismuth tellurides were determined using an electromotive force (EMF) method with a glycerol electrolyte in a temperature range from 300 to 450 K. The solid-phase equilibrium diagram of the GeTe-Bi2Te3-Te system at 400 K was constructed using X-ray diffraction (XRD) and scanning electron miscroscope (SEM) techniques of synthesized electrode alloys, as well as available literature data. It is found that all telluride phases in GeTe-Bi2Te3 pseudo-binary section have a tie-line connection with elemental tellurium. The relative partial thermodynamic functions of GeTe in alloys were calculated using data from EMF measurements of concentration cells relative to the GeTe electrode. These findings together with the corresponding thermodynamic functions of GeTe and Bi2Te3 were used to calculate the relative partial molar functions of germanium in alloys, and also the standard thermodynamic functions of formation and standard entropies of the ternary compounds, namely Ge2Bi2Te5, Ge3Bi2Te6 and Ge4Bi2Te7.

Experimental and numerical study of temperature evolution and hydrogen desorption process on an amorphous alloy Mg50Ni50

In the present study, we explored the temperature evolution and hydrogen desorption properties of the Mg50Ni50 alloy through both numerical simulation and experimental analyses. Desorption kinetics characterization was carried out using the volumetric method, specifically employing a Sievert's-type apparatus to investigate solid-gas reactions. The experiments covered a temperature range from 313 K to 353 K, with an initial hydrogen pressure of 12 bar. Simultaneously, a mathematical approach was employed to numerically investigate the temperature evolution within the hydride bed. Using COMSOL Multiphysics as a simulator, a numerical simulation was conducted based on experimental data. The study examined the impact of cooling temperature on hydride temperature evolution. Results revealed that hydrogen desorption kinetics of the amorphous Mg50Ni50 alloy are more significant compared to those of Mg2Ni compounds. Moreover, the effect of the warming temperature on the equilibrium pressure can also be observed in the hydrogen desorption isotherm curves. The experimental study of the Mg50Ni50 alloy provided activation energy data, along with determination of hydride formation enthalpy and entropy. On the other hand, we showed that the hydride temperature is maximum at the hydride-hydrogen interface within the hydride center.

Thermodynamic insights of ternary compounds of NiO - V2O5 system

We present the first experimental investigation on thermochemical stability of three ternary nickel vanadates, namely, NiV2O6(s), Ni2V2O7(s) and Ni3V2O8(s) in the NiO-V2O5 system. The standard molar entropies of formation of the compounds were determined by low temperature heat capacity measurements from 2 to 300 K using relaxation calorimetry. The standard molar enthalpy of formation and molar heat capacities were determined employing high temperature oxide melt solution calorimetry in conjunction with differential scanning calorimetry. Using the experimentally obtained thermochemical data, the standard molar Gibbs energy of formation of these compounds were derived and the corresponding expressions are given as follows:∆Gf,m°<NiV2O6>±1.4kJmol−1=−1839.4+0.5132(T/K)(T:298.15−1000K)∆Gf,m°<Ni2V2O7>±1.4kJmol−1=−2101.8+0.5971(T/K)(T:298.15−1000K)∆Gf,m°<Ni3V2O8>±3.2kJmol−1=−2360.5+0.6538(T/K)(T:298.15−1000K)

Thermodynamic analysis of cellulose nitration

In this study, the standard formation enthalpies and entropies of cellulose and nitrocellulose samples were determined. These characteristics were used for thermodynamic analysis of bulk nitration of the entire cellulose sample and local nitration only of amorphous domains (ADs) of cellulose. It was found that the reaction of bulk nitration of cellulose up to a substitution degree (DS) of 1.5 is endothermic and determined primarily by the contribution of the temperature-entropy component to the negative Gibbs potential. However, if DS is higher than 1.5, the bulk nitration becomes exothermic and its feasibility is determined by the impact of enthalpy on the Gibbs potential. In the case of local nitration of cellulose ADs, the main contribution to the Gibbs potential is made by the reaction enthalpy that determines the feasibility of this process. It was shown that with the enhancement in DS of nitrocellulose, the negative value of the Gibbs potential of the reaction increases. Thus, the cellulose nitration to higher DS is thermodynamically favorable. Since the locally nitrated samples are copolymers of amorphous nitrocellulose and crystalline cellulose, they should be significantly less hydrophilic than cellulose. Therefore, it can be expected that the local nitration method will find a wide practical application for inexpensive hydrophobization of cellulose materials.

Investigating entangled photons to quantify quantum correlations in dual optomechanical cavities.

Quantum correlations that go beyond quantum entanglement have a significant role in the fields of quantum information processing and quantum computation. In essence, when we describe a quantum system using pure states, quantum entanglement and quantum correlation are essentially indistinguishable. However, this equivalence breaks down when dealing with general mixed states. To contribute to understanding this distinction, we have considered a straightforward model for both generating and measuring these quantum correlations. We focus on two macroscopic mechanical resonators situated in separate Fabry–Perot cavities and coupled through the photon hopping process. Our model allows us to conduct a comprehensive examination and quantification of quantum correlations that extend beyond entanglement between these mechanical modes. Our approach begins with the determination of the global covariance matrix, serving as the foundation for calculating two key metrics: the Entropy of Formation and the Gaussian quantum Discord. These metrics enable us to quantify the extent of quantum entanglement and quantum correlations, respectively. Our analysis, based on these quantifiers, reveals that quantum discord serves as a more appropriate metric for characterizing the quantum correlations between the mechanical modes in an optomechanical quantum system, especially in the presence of robust photon hopping.

Thermodynamics of complex formation of silver(I) with substituted pyridines and cyclic amines in non-aqueous solvents

The understanding of the thermodynamic stability and speciation of metal complexes in solution requires access to their enthalpy and entropy of formation. In this work, we specifically focus our investigation on the complexation process of silver(I) ion in acetonitrile (AN) with substituted mono pyridines and cyclic monoamines. The aim of this study is to provide reliable thermodynamic data to obtain insights on metal complex formation, focusing on ligands donor properties and solvation effects. Carefully designed potentiometric and calorimetric experiments allowed to define the species present at different ligand/metal ratios and to obtain the complex formation constants and enthalpies. In general, the enthalpy terms associated with the complex formation are highly exothermic, while the entropy values are always unfavorable. The formation constants of AgLj species for the ligands investigated in AN are compared with those previously obtained in dimethyl sulfoxide (DMSO) and water. The trends in stability constants and enthalpy values are discussed in relation to the pKa data available in the different solvents. Higher pKa values correspond to greater ligand basicity and result in more stable and more enthalpy stabilized complexes.

A first-principles investigation of internal energy and entropy of formation of charged defects in Th1−xUxO2 (x ≤ 0.5)

Mixed thorium/uranium dioxide, (Th,U)O2, is under consideration for advanced nuclear fuel applications. Investigating the point defect structure and energy in this oxide is important for predicting its behavior as fuel. In this work, we use first-principles calculations based on the generalized gradient approximation (GGA)+Hubbard U approach to investigate the internal energy and entropy of the formation of point defects in Th1−xUxO2 at various compositions below x ≤ 0.5. Point defects including O vacancies, O interstitials, Th vacancies, Th interstitials, U vacancies, and U interstitials have all been considered with their charges ranging from neutral to the maximum nominal values. The observed trends have been explained in terms of electronic density of states. The valence band maxima of crystals that contain defects play a crucial role and exhibit variations depending on the U content and the applied charge. The temperature dependence of internal energy and entropy of formation of defects have also been examined. The internal energy of formation of defects was found to exhibit slowly varying or constant values with respect to changes in the U content, except at low values of x and low temperatures. The entropy of formation of defects was observed to decrease with increasing U content. It was additionally observed that the entropy of formation of vacancies increases with temperature, while that of interstitials decreases. This investigation further revealed that at 0 K, the cation vacancies and anion interstitials become increasingly favorable with increasing U content, while cation interstitials and anion vacancies become less favorable.

Thermodynamic and kinetic study of the thermal dehydrogenation of Sr(AlH4)2 taking into account the by-products NaCl and LiCl

The presented work sets out to investigate the influence of LiCl and NaCl, the typical by-products of the mechanochemical synthesis of complex metal hydrides such as alanates and boranates, on the kinetics and thermodynamics of the dehydrogenation of Sr(AlH4)2. We found no effect of NaCl on the decomposition pathway of Sr(AlH4)2. Although LiCl does not affect the first dehydrogenation to SrAlH5, it does alter the further decomposition to the final products. Thermodynamic properties such as the heat capacity functions, enthalpies of formation and absolute entropies were determined for Sr(AlH4)2 itself and its decomposition product SrAlH5 within this study.

Heat Capacity Function, Enthalpy of Formation and Absolute Entropy of Mg(AlH4 )2.

In this investigation, we set out first to characterize the thermodynamics of Mg(AlH4 )2 and secondly to use the determined data to reevaluate and update existing estimation procedures for heat capacity functions, enthalpies of formation and absolute entropies of alanates. Within this study, we report the heat capacity function of Mg(AlH4 )2 in the temperature range from 2 K to 370 K and its enthalpy of formation and absolute entropy at 298.15 K, being kJ mol-1 and 133.06 J (K mol)-1 , respectively. Using these values, we updated and expanded methods for the estimation of thermodynamic data of alanates.

Modeling the thermochemistry of nitrogen-containing compounds via group additivity.

First-principles based kinetic modeling is essential to gain insight into the governing chemistry of nitrogen-containing compounds over a wide range of technologically important processes, e.g. pyrolysis, oxidation and combustion. It also enables the development of predictive, fundamental models key to improving understanding of the influence of nitrogen-containing compounds present as impurities or process additives, considering safety, operability and quality of the product streams. A prerequisite for the generation of detailed fundamental kinetic models is the availability of accurate thermodynamic properties. To address the scarcity of thermodynamic properties for nitrogen-containing compounds, a consistent set of 91 group additive values and three non-nearest-neighbor interactions has been determined from a dataset of CBS-QB3 calculations for 300 species, including 104 radicals. This dataset contains a wide range of nitrogen-containing functionalities, i.e. imine, nitrile, nitro, nitroso, nitrite, nitrate and azo functional groups. The group additivity model enables the approximation of the standard enthalpy of formation and standard entropy at 298 K as well as the standard heat capacities over a large temperature range, i.e. 300-1500 K. For a test set of 27 nitrogen-containing compounds, the group additivity model succeeds in approximating the ab initio calculated values for the standard enthalpy of formation with a MAD of 2.3 kJ mol-1. The MAD for the standard entropy and heat capacity is lower than 4 and 2 J mol-1 K-1, respectively. For a test set of 11 nitrogen-containing compounds, the MAD between experimental and group additivity approximated values for the standard enthalpy of formation amounts to 2.8 kJ mol-1.

Thermodynamic properties of chalcogenide and pnictide ternary tetrahedral semiconductors

In this paper, we present thermodynamic properties such as heat of formation, heat of fusion and entropy of fusion for chalcopyrite structured solids with the product of ionic charges and nearest neighbour distance d (Å). The heat of formation (∆Hf) of these compounds exhibit a linear relationship when plotted on a log-log scale against the nearest neighbour distance d (Å), but fall on different straight lines according to the ionic charge product of the compounds. On the basis of this result two simple heat of formation (∆Hf)heat of fusion (∆HF), and heat of formation (∆Hf)entropy of fusion (∆SF), relationship are proposed and used to estimate the heat of fusion (∆HF) and entropy of fusion (∆SF) of these semiconductors. We have applied the proposed relation to AIIBIVC2 V and AI BIIIC2 VI chalcopyrite semiconductor and found a better agreement with the experimental data than the values found by earlier researchers. The results for heat of formation differ from experimental values by the following amounts: 0.3% (CuGaSe2), 6.7% (CuInSe2), 5% (AgInSe2), 5% (ZnGeP2), 6% (ZnGeP2), 0.4% (ZnSnP2), 0.7% (ZnSiAs2), 2.6% (ZnGeAs2), 1.2% (ZnSnAs2), 3.8% (CdGeP2), 6.4% (CdGeAs2), the results for heat of fusion differ from experimental values by the following amounts: 2.6% (CuGaS2), 0.6% (CuInTe2), 6% (ZnGeAs2), 8.8% (ZnSiAs2) and the results for entropy of fusion differ from experimental values by the following amounts: 6% (CuInSe2), 8% (CdSiP2).

Potential of Knudsen Effusion Mass Spectrometry (KEMS) for Energy Materials Science

The determination of valuable thermodynamic data for materials at elevated temperatures is a very important issue in Materials Science. This can be achieved by the elucidation of vaporization processes with mass spectrometric techniques.Knudsen Effusion Mass Spectrometry provides the identification of gaseous species present above condensed phases and permits the determination of their partial pressures up to a total pressure of 200 Pa.The key for establishing model calculations using DG minimization tools like among others FactSage, Pandat or Thermocalc is the knowledge of the thermodynamic data of molecules and compounds. This includes the partial pressures of gaseous species, the standard enthalpies and entropies of formation of gaseous and condensed phases as well as their enthalpies and entropies of mixing and the knowledge of phases and chemical compounds which are formed upon reactions.The method will be described and examples and an insight will be given how basic thermodynamic data are derived with the above mentioned method for the incorporation into thermodynamic databases. Examples of investigations carried out in our lab will be given.The number of groups worldwide using this advanced technology has been shrinking during the last decades. Therefore, we are pleased to announce the setup of a completely new designed instrument in our laboratory which can determine data with higher precision and better resolution.The new set up will be presented as well.