Standard Thermodynamic Functions Research Articles

Solid-phase Relationships in the Tl2Te-Tl2Te3-TlTbTe2 System and Thermodynamic Properties of Thallium–Terbium Tellurides

This work presents new data on the solid-phase equilibria of the Tl-Tb-Te ternary system in the Tl2Te-Tl2Te3-TlTbTe2 composition region and the thermodynamic functions of the TlTbTe2, and Tl9TbTe6 ternary compounds. Studies were carried out by using the electromotive forces method (EFM) and the powder x-ray diffraction technique. From the EMF measurements of the concentration cells of the type (−) TbTe (s) | glycerol + KCl + TbCl3 | (Tb in Tl-Tb-Te alloys) (s) (+) in the 300-450 K temperature interval, the relative partial thermodynamic functions of TbTe and Tb in alloys of the Tl2Te3-TlTe-TlTbTe2, and TlTe-TlTbTe2-Tl9TbTe6 three-phase regions were determined. Based on the solid-phase equilibria diagram, the potential-forming reactions responsible for the indicated partial molar quantities were determined and the standard thermodynamic functions of formation and standard entropies of the TlTbTe2 and Tl9TbTe6 ternary compounds were calculated.

Refinement of the Phase Diagram of the Bi-Te System and the Thermodynamic Properties of Lower Bismuth Tellurides

Alloys of the system Bi-Te obtained by long-term thermal annealing of samples quenched from 1000 K were studied by differential thermal analysis, x-ray phase diffraction, and scanning electron microscopy methods, as well as by electromotive forces measurements (EMF) of concentration cells relative to a bismuth electrode. A new refined version of the phase diagram which reflects the compounds Bi2Te3, Bi4Te5, Bi8Te9, BiTe, Bi4Te3, Bi2Te, and Bi7Te3 with practically constant compositions was constructed. It was found that all of these compounds, except for Bi2Te3, melt with decomposition by peritectic reactions. Based on powder diffraction patterns, the types and parameters of the crystal lattices of these compounds were determined. The EMF measurements were used to determine the partial molar functions of bismuth in the alloys and the standard integral thermodynamic functions of bismuth tellurides.

Thermodynamic study of a synthetic analog of the famatinite mineral - Cu3SbS4

Fundamental thermodynamic properties of the synthetic analog of the famatinite mineral - Cu3SbS4 were studied on the basis of electromotive force (EMF) measurements. The EMF of the concentration chains relative to the Cu electrode with a solid electrolyte was measured for the alloys from the Cu3SbS4 + Sb2S3 + S phase region at 300-380K temperature interval. Based on measurement data, the relative partial thermodynamic functions of copper in alloys, the standard thermodynamic functions of formation, as well as, the standard entropy of the Cu3SbS4 ternary compound were calculated for the first time.

Thermodynamics of transfer and partition of 3,5-diamino-1-phenyl-1,2,4-triazole in the 1-octanol/water biphasic system

In this paper, we focus for the first time on thermodynamics of transfer of 3,5-diamino-1-phenyl-1,2,4-triazole (DAPT) from water to liquid 1-octanol which is considered in pharmaceutical chemistry as an appropriate model of a lipid-like environment for studying a passive membrane transport of various drugs. The enthalpies of solution of DAPT have been determined calorimetrically in both solvents at 298.15, 308.15 and 328.15 K. The partition coefficients (P) have been obtained in the 1-octanol/water biphasic system at 298.15 and 328.15 K using a classical isothermic saturation method. Standard thermodynamic functions of DAPT transfer from water to a lipid-like phase have been calculated via the Gibbs–Helmholtz equation using the temperature dependence of the standard enthalpies of solution and the partition coefficient at the reference temperature of 298.15 K. We have found that the enthalpic term favours the solute transfer both at lower and elevated temperatures, whereas the entropic one contributes in the opposite manner. The free energy of transfer remains negative for all the temperature range studied indicating rather appreciable affinity of a potential drug towards a lipid-like environment. The comparison of the experimental and calculated P values indicates that our approach is able to predict with a good accuracy the behaviour of the 1,2,4-triazole derivatives for the physiological temperature range.

Heat Capacity and Thermodynamic Functions of Neodymium Orthoniobate

The heat capacity of polycrystalline neodymium orthoniobate NdNbO4 in the range 2–1370 K is studied by relaxation, adiabatic, and differential scanning calorimetry. The existence of a magnetic transformation with a Neel temperature below 2 K in the low-temperature region is verified. The reversible phase transition at 987 K is shown to be a second-order transition. The contribution of the Schottky anomaly (Schottky contribution) to neodymium orthoniobate heat capacity is estimated. The gained data are used to calculate temperature-dependent standard thermodynamic functions in the range from 0 to 1400 K. Their values at 298.15 K are $$C_{p}^{^\circ }$$ (298.15 K) = 121.4 ± 0.4 J/(K mol), S°(298.15 K) = 134.7 ± 0.5 J/(K mol), H°(298.15 K) – H°(0 K) = 21.24 ± 0.17 kJ/mol, Ф°(298.15 K) = 63.43 ± 0.21 J/(K mol).

A combined experimental and theoretical study of miconazole salts and cocrystals: crystal structures, DFT computations, formation thermodynamics and solubility improvement.

Experimental and theoretical screening of multi-component crystal forms of miconazole (MCL), an antifungal drug, with ten aliphatic dicarboxylic acids was performed. Seven multi-component molecular crystals were isolated and identified by different analytical techniques, including the powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and solubility methods. The crystal structures of the MCL hemihydrate, two cocrystals with succinic ([MCL + SucAc] (2 : 1)) and fumaric acids ([MCL + FumAc] (2 : 1)) and one salt with maleic acid ([MCL + MleAc] (1 : 1)) were redetermined. The new cocrystal of MCL with adipic acid ([MCL + AdpAc] (2 : 1)) was investigated by single crystal X-ray diffractometry. It was found that the AdpAc molecule in the cocrystal has an unusual anticlinal conformation. The combination of periodic density functional theory (DFT) computations and quantum topology analysis confirmed the structure-directing role of the acid-imidazole heterosynthon for the considered crystals. The melting temperatures of all the studied multi-component crystals are between the values of the corresponding individual components except [MCL + MleAc] (1 : 1). A thermal analysis has shown that the thermodynamic and thermophysical characteristics of the considered two-component molecular crystals are strongly dependent both on specific interactions (presence of sites of donor-acceptor interactions and hydrogen bond formation) and on nonspecific interactions - molecule polarizability. Based on the sublimation thermodynamics database of molecular crystals, the standard sublimation thermodynamic functions of MCL were evaluated. The thermodynamic functions of multi-component crystal formation based on MCL were calculated and analyzed. Solubility experiments on the MCL multi-component crystals were carried out in isotonic aqueous buffer solutions at pH 1.2 and 6.8 and compared with the solubility of the MCL free base and its nitrate salt. It was found that the salt/cocrystal formation of MCL with dicarboxylic acids considerably increased the MCL solubility in pH 6.8 buffer. The biggest MCL solubility enhancement was observed in the [MCL + TartAc] (1 : 1) salt. The solubility value of MCL in the [MCL + TartAc] (1 : 1) salt is commensurate with the commercial MCL nitrate salt.

Thermodynamıc Propertıes of the BiTe and Bi8Te9 Compounds

Two-phase alloys Bi8Te9+Bi4Te5 and BiTe+Bi8Te9 were studied by the electromotive forces method (EMF) in the temperature range 300-450 K. From the EMF data, the relative partial molar functions of bismuth in the alloys were calculated. The potential-forming reactions responsible for these partial functions were compiled, the values of the standard thermodynamic functions of formation, and the standard entropies of Bi8Te9 and BiTe compounds were calculated. A comparative analysis of the data for BiTe with the literature data was carried out; for Bi8Te9, the thermodynamic functions were obtained for the first time.

Sorption and Isomerselective Properties of Binary Sorbent Based on Supramolecular 4-(3-Hydroxypropyloxy)-4'-Formylazobenzene Liquid Crystal and Partially Methylated β-Cyclodextrin

The sorption and selective properties of a composite sorbent based on the supramolecular liquid crystal 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and partially methylated β-cyclodextrin heptakis-(2,6-di-O-methyl)-β-cyclodextrin (Me2,6-β-CD) have been studied by inverse gas chromatography. The standard thermodynamic functions of sorption on the smectic A phase of the sorbent for 29 volatile organic compounds of different classes were determined and compared with similar functions obtained on a column with “pure” HPOFAB. The reasons for the increase in the retention of all studied compounds (except for the optical isomers of butanediol-2,3) when Me2,6-β-CD (10 wt. %) added to HPOFAB are discussed. It was found that the mixed SA phase of the binary sorbent in conditions of gas-liquid chromatography has moderate values of structural selectivity and enantioselectivity to both low-polar terpene hydrocarbons and polar optical isomers (butanediols-2,3).

Thermodynamic Properties of AuSb2

We have for the first time determined the temperature dependence of heat capacity for aurostibite, AuSb2, by adiabatic calorimetry and calculated its standard thermodynamic functions in a wide temperature range. At a temperature of 298.15 K, we have obtained $$C_{p}^{^\circ }$$ = 76.01 ± 0.15 J/(mol K), S° = 133.4 ± 0.3 J/(mol K), Н°(298.15 K) − Н°(0)= 17.39 ± 0.03 kJ/mol, and Ф° = 75.02 ± 0.15 J/(mol K). Using previously reported data and the present results, we have found ΔfG°(298.15) = −11.36 ± 0.90 kJ/mol.

The Relative Thermodynamic Stability of Diamond and Graphite.

Recent density-functional theory (DFT) calculations raised the possibility that diamond could be degenerate with graphite at very low temperatures. Through high-accuracy calorimetric experiments closing gaps in available data, we reinvestigate the relative thermodynamic stability of diamond and graphite. For T<400 K, graphite is always more stable than diamond at ambient pressure. At low temperatures, the stability is enthalpically driven, and entropy terms add to the stability at higher temperatures. We also carried out DFT calculations: B86bPBE-25X-XDM//B86bPBE-XDM and PBE0-XDM//PBE-XDM results overlap with the experimental -TΔS results and bracket the experimental values of ΔH and ΔG, displaced by only about 2× the experimental uncertainty. Revised values of the standard thermodynamic functions for diamond are Δf Ho =-2150±150 J mol-1 , Δf So =3.44±0.03 J K-1 mol-1 and Δf Go =-3170±150 J mol-1 .

The Relative Thermodynamic Stability of Diamond and Graphite

AbstractRecent density‐functional theory (DFT) calculations raised the possibility that diamond could be degenerate with graphite at very low temperatures. Through high‐accuracy calorimetric experiments closing gaps in available data, we reinvestigate the relative thermodynamic stability of diamond and graphite. For T&lt;400 K, graphite is always more stable than diamond at ambient pressure. At low temperatures, the stability is enthalpically driven, and entropy terms add to the stability at higher temperatures. We also carried out DFT calculations: B86bPBE‐25X‐XDM//B86bPBE‐XDM and PBE0‐XDM//PBE‐XDM results overlap with the experimental −TΔS results and bracket the experimental values of ΔH and ΔG, displaced by only about 2× the experimental uncertainty. Revised values of the standard thermodynamic functions for diamond are ΔfHo=−2150±150 J mol−1, ΔfSo=3.44±0.03 J K−1 mol−1 and ΔfGo=−3170±150 J mol−1.

Thermophysical characterization of TeO2-WO3-Bi2O3 glasses for optical applications

Heat capacity, glass transition and crystallization characteristics of high-purity tungsten-tellurite glasses (78-x)TeO2–22WO3-xBi2O3 (x = 2, 5, 8 mol%) were studied by differential scanning calorimetry in the temperature range of 300–950 K. Density and coefficient of thermal expansion (CTE) were measured at the room temperature. Density increases from 5.94 to 6.32 ± 0.02 g/cm3 with an increase in the content of Bi2O3. CTE at 298 K is equal to (36.3 ± 0.6)⋅10-6 K−1 for the series. As a result of theoretical processing of calorimetric and volumetric data, standard thermodynamic functions, density and CTE were calculated for each glass composition in a wide temperature ranges, and a method for their parametric prediction was proposed for intermediate unstudied compositions. The most crystallization resistant compositions of glasses were revealed. The obtained thermodynamic parameters, including temperature dependences of density and CTE, are useful for the production of bismuth-containing tellurite glasses and for predicting their properties.

Phase Equilibria in the Ag2Te-PbTe-Sb2Te3 System and Thermodynamic Properties of the (2PbTe)1-x(AgSbTe2)x Solid Solutions

Phase equilibria in the Ag2Te-PbTe-Sb2Te3 system were experimentally investigated by means of differential thermal analysis, powder X-ray diffraction techniques and electromotive force (EMF) measurement method. A liquidus surface projection of the system, 750 K and 300 K isothermal sections, as well as five vertical sections of the phase diagram, were constructed. The primary crystallization fields of phases and homogeneity range of phases were also determined. The character and temperature of the various nonvariant and monovariant equilibria were identified. The studied sys-tem is characterized by the formation of a wide continuous band of a high-temperature cubic structured solid solution (?-phase) between PbTe and Ag1-xSb1 + xTe2 + x intermediate phase. The partial molar thermodynamic functions of lead telluride in alloys and standard integral thermodynamic functions of the ?-solid solutions along the 2PbTe-AgSbTe2 section were calculated based on the EMF measurements results.

Conductometric and Refractometric Studies of 1-Propyl-3-methylimidazolium Bromide Ionic Liquid in Water + Ethylene Carbonate Mixtures at T = (298.2, 308.2 and 318.2) K

In this work, we determined thermophysical properties such as electrical conductivity and refractive index for 1-propyl-3-methylimidazolium bromide, [PrMIm]Br in ternary mixtures of [PrMIm]Br + ethylene carbonate + water at T = (298.2, 308.2 and 318.2) K and 0.1MPa. Conductometric measurements were carried out for [PrMIm]Br ionic liquid in ethylene carbonate + water solvent mixture in various composition 10, 20 and 30 mass% of ethylene carbonate (EC) in the ionic strength ranging from 0.0029 to 0.2500 mol.kg-1. These data were treated by Fuoss-Onsager equation, and the values of limiting molar conductivity ( ) and ion association constant (KA) were obtained. These results used to calculate the Walden product ( ) and the corresponding standard thermodynamic functions of ion association process including Gibbs free energy ( ), enthalpy ( ) and entropy ( ) for the investigated system. In addition, refractive indices were measured for the binary and ternary [PrMIm]Br + water + EC mixtures at T = (298.2, 308.2 and 318.2) K. The refractive index deviations (ΔnD) were calculated and the binary and ternary data of ΔnD were correlated using Redlich-Kister and the Cibulka equations, respectively. Also, the measured refractive indices were compared to the calculated values using some mixing rules.

Anomalous Behavior of Heat Capacity in Ni2(bdc)2(dabco). Schottky Anomaly and Spin–Phonon Interaction

Temperature dependence of molar heat capacity of Ni2(bdc)2(dabco) was first measured by the method of vacuum adiabatic calorimetry in the temperature region of 5–295 K. A heat capacity anomaly was discovered above 60 K. The analysis of the electronic structure of a dimeric complex Ni2(O2C-)4 testifies that the observed anomaly is the Schottky anomaly caused by thermal excitation of d electrons of Ni2+(3d8) ions. The experimental heat capacity values in the vicinity of the maximum of the Schottky anomaly exceed its calculated values by ∼10%. This fact is explained by the spin–lattice interaction between d electrons of Ni2+ ions and lattice vibrations of Ni-DMOF (Ni2(bdc)2(dabco)). The obtained experimental Cp values were used to calculate standard thermodynamic functions (heat capacity, enthalpy, and entropy) of the studied compound.

On the equipartition theorem and black holes non-Gaussian entropies

In this letter we have shown that, from the standard thermodynamic functions, the mathematical form of an equipartition theorem may be related to the algebraic expression of a particular entropy initially chosen to describe the black hole event horizon. Namely, we have different equipartition expressions for distinct statistics. To this end, four different mathematical expressions for the entropy have been selected to demonstrate our objective. Furthermore, a possible phase transition is observed in the heat capacity behavior of the Tsallis and Cirto entropy model.

Thermodynamic investigations of the erbium tellurides by EMF method

The work presents the results of a thermodynamic study of the Er-Te system by the method of electromotive forces (EMF) in the temperature range of 300-450 K. From the EMF measurements of the concentration cells relative to the Er and ErTe electrodes, the partial thermodynamic functions of ErTe and Er in the alloys are determined, based on which the standard thermodynamic formation functions and the standard entropies of the intermediate compounds ErTe3, Er2Te3, and ErTe are calculated. A comparative analysis of the obtained data with the literature is carried out.

Thermodynamic Characteristics of the Dissolution of Fullerene C60 in Benzene, Toluene, o-Xylene, o-Dichlorobenzene, and Carbon Disulfide at Different Temperatures

The enthalpy of the fullerene C60 dissolution in carbon disulfide CS2 at 298.15 K was measured in a calorimeter with an isothermal shell. The value of the standard enthalpy of the fullerene C60 dissolution in this substance was found. Standard thermodynamic functions of fullerene C60 dissolution in benzene, chlorobenzene, bromobenzene, carbon disulfide, toluene, o-xylene, and o-dichlorobenzene at 298.15 K were determined based on the results of thermometric measurements and theoretical data. The standard thermodynamic functions have also been determined for toluene, o-xylene, and o-dichlorobenzene at temperatures of 288.15 and 308.15 K. The possible causes of the abnormal temperature dependence of the fullerene C60 solubility in some solvents, as well as sign changes in their dissolution enthalpies, in the temperature range of 288.15--308.15 K have been discussed

Heat capacity and standard thermodynamic functions of the fullerenol C60(OH)24

In the present investigation, the heat capacity of fullerenol C60(OH)24 was measured by precision adiabatic and differential scanning calorimetry over the temperature range from T = (6 to 670) K. The keto-enol tautomerism was revealed in the temperature range T = (355–575) K and enthalpy of transition was determined. The standard thermodynamic functions: molar heat capacity Cp°, enthalpy [H°(T) − H°(0)], entropy S°(T), and Gibbs energy [G°(T) − H°(0)] of the fullerenol were determined over the temperature range from T = (6 to 350) K from the obtained experimental results. Also, DFT calculations of the heat capacities were performed. The standard thermodynamic properties of the investigated fullerenol were compared to other fullerene derivatives.

Stacked-cup multiwall carbon nanotubes as components of energy-intensive suspension jet fuels

Objectives. The addition of high-density carbon materials to jet fuels can lead to a significant increase in the volumetric energy of the fuel combustion. The purpose of the current study was to thermodynamically analyze the possibility of obtaining model hydrocarbon fuels from toluene and T-1 using stacked-cup multiwall carbon nanotubes (MWCNTs). Methods. Bomb combustion calorimetry was used to define the combustion energy of the MWCNTs in the crystalline state. The temperature dependence of the MWCNTs’ heat capacity in the range 5–370 K and the fusion parameters were estimated using low-temperature adiabatic calorimetry. The physical density of MWCNTs was measured using the pycnometric method. The sedimentation stability of the mixtures of MWCNTs with liquids was determined using centrifugation at 7000 g. The calculations were carried out in MS Excel. Results. The energy and enthalpy of combustion of a technical sample of MWCNTs in the crystalline state were determined. Based on the smoothed heat capacity values, the standard thermodynamic functions (enthalpy, entropy, and Gibbs reduced energy) of MWCNTs in the crystalline state were obtained in a temperature range of 0–2000 K. The extrapolation of the MWCNTs’ heat capacity was carried out at a temperature of up to 2000 K using the heat capacity of crystalline graphite. It has been established that mixtures of MWCNTs with liquids containing more than 33 mass % of MWCNTs are stable during centrifugal sedimentation at 7000 g. For the toluene–MWCNTs and fuel T-1–MWCNTs model systems, the specific and volumetric combustion energies, the adiabatic combustion temperatures, and the conditional final maximum speed of the model rockets with fuel of various compositions were also calculated. Conclusions. The thermodynamic analysis showed that the addition of MWCNTs can significantly increase the volumetric energy intensity of traditional jet fuels, which can in turn improve the operational characteristics of drones and rockets.