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Anharmonic effects play a crucial role in determining thermochemical properties of liquids and gases. For such extended phases, the inclusion of anharmonicity in reliable electronic structure methods is computationally extremely demanding, and hence, anharmonic effects are often lacking in thermochemical calculations. In this study, we apply the quantum cluster equilibrium method to transfer density functional theory calculations at the cluster level to the macroscopic, liquid, and gaseous phase of hydrogen fluoride. This allows us to include anharmonicity, either via vibrational self-consistent field calculations for smaller clusters or using a regression model for larger clusters. We obtain the structural composition of the fluid phases in terms of the population of different clusters as well as isobaric heat capacities as an example for thermodynamic properties. We study the role of anharmonicities for these analyses and observe that, in particular, the dominating structural motifs are rather sensitive to the anharmonicity in vibrational frequencies. The regression model proves to be a promising way to get access to anharmonic features, and the extension to more sophisticated machine-learning models is promising. [ABSTRACT FROM AUTHOR]

Vapor–liquid equilibria and thermodynamic properties of saturated argon and krypton were calculated by semi-classical Monte Carlo simulations with the NpT + test particle method using ab initio potentials for the two-body and nonadditive three-body interactions. The NpT + test particle method was extended to the calculation of second-order thermodynamic properties, such as the isochoric and isobaric heat capacities or the speed of sound, of the saturated liquid and vapor by using our recently developed approach for the systematic calculation of arbitrary thermodynamic properties in the isothermal–isobaric ensemble. Generally, the results for all simulated properties agree well with experimental data and the current reference equations of state for argon and krypton. In particular, the results for the vapor pressure and for the density and speed of sound of the saturated liquid and vapor agree with the most accurate experimental data for both noble gases almost within the uncertainty of these data, a level of agreement unprecedented for many-particle simulations. This study demonstrates that the vapor–liquid equilibrium and thermodynamic properties at saturation of a pure fluid can be predicted by Monte Carlo simulations with high accuracy when the intermolecular interactions are described by state-of-the-art ab initio pair and nonadditive three-body potentials and quantum effects are accounted for. [ABSTRACT FROM AUTHOR]

As part of a series of studies of hydrogen‐atom transfer or tautomerization reactions of imidic acid‐amide species, H${\text{H}}$─O${\text{O}}$─C${\text{C}}$═N${\text{N}}$─ ⇌O$\rightleftharpoons {\text{O}}$═C${\text{C}}$─NH${\text{NH}}$─, we report the rate constants for a set of 16 four‐membered cyclic compounds at low, 50–300 K, and high, 500–1500 K, temperatures. The compounds are labeled according to the two ring groups X and Y, which can be CH2${\text{CH}}_{2}$, NH, CH, N, O, or C(O) and which are at some remove from the reactive site. These rate constants are for both the direct reaction and for that mediated by an additional water molecule, which facilitates the hydrogen transfer reaction. In the latter case, we show that the rate of reaction from a pre‐reaction complex is rapid at temperatures down to 50 K and dominated by quantum mechanical effects as evaluated by small‐curvature and quantized‐reaction‐states tunneling. In addition, we present thermochemical data such as enthalpies of formation, entropies, isobaric heat capacities, and enthalpy functions for these largely unknown species, which span a range of compounds from β$\beta$‐propiolactone to 1,3‐diazetidine‐2,4‐dione. [ABSTRACT FROM AUTHOR]

In the present study, the isobaric heat capacity of ultralight magnesium-lithium alloys with composition of 21, 25 and 30 at. pct Li were measured in the temperature range 185–775 K, most measurements were made for the first time. Measurements were performed by the method of differential scanning calorimetry using a DSC 404 F1 setup. The estimated uncertainty of the obtained results was 2–3 pct. The temperature dependences and the tables of recommended data on their basis were developed for scientific and practical application. For all studied Mg-Li alloys an abrupt change in the heat capacity was observed at the temperatures of about 220–260 K, which is apparently caused by the martensitic phase transformation. It was found that the specific molar heat capacity values of Mg-Li alloys containing 21–30 at. pct Li in the temperature interval of 250–685 K practically coincide with each other and can be estimated within the limits of DSC measurement uncertainties using the heat capacity temperature dependence of solid magnesium. It is possible to estimate the heat capacity of the studied alloys (with an accuracy not exceeding the measurement uncertainty) using the Neumann-Kopp rule, but in a much narrower temperature range of 250–456 K. [ABSTRACT FROM AUTHOR]

The isobaric heat capacities of acetone and its binary aqueous solutions were measured using a heat capacity meter (IT-s-400). The measurements were performed at temperatures from 323.15 to 453.15 K and pressures below 19.6 MPa for acetone and at temperatures from 348.15 to 473.15 K and the same pressures for its solutions, at concentrations of 2.5, 3.5, and 5 wt % acetone. The expanded uncertainty of heat capacity, pressure, temperature, and concentration measurements at a 95% confidence level with a coverage factor k = 2 was estimated at 2.4%, 0.05%, 15 mK, and 0.001, respectively. The results were compared with the literature data in the given ranges of state parameters. [ABSTRACT FROM AUTHOR]

This study explores the principal modes of high-pressure transcritical channel flow from direct numerical simulation data. The four cases investigated correspond to CO2 at high-pressure conditions (P / P c = 1.5) confined between a cold/bottom wall (T / T c = 0.8 − 0.95) and a hot/top wall (T / T c = 1.1 − 1.4); P c and T c correspond, respectively, to the pressure and temperature of the critical point. The bulk velocity ranges between U b = 0.5 − 1.0 m / s with corresponding bulk Reynolds numbers of R e b ≈ 1000 − 2500. The four cases considered are first characterized into laminar and turbulent regimes, followed by an analysis of energy decay using singular value decomposition. This method allows us to identify the most energetic modes of velocity, temperature, and specific isobaric heat capacity for the laminar and turbulent cases considered. The results reveal that fewer modes are needed to represent the hydrodynamics compared to the thermodynamics of the system. The findings also highlight that the pseudo-boiling region, prevalent in high-pressure transcritical systems, disrupts the coherent structures formed (especially) in the hotter region of the flow. Finally, a correlation analysis between the most energetic modes shows an interdependence between velocity and specific isobaric heat capacity modes when conditioned to focus solely on the pseudo-boiling affected regions. This correlation underscores the complex interplay between hydrodynamic and thermodynamic variables in such high-pressure transcritical environments. [ABSTRACT FROM AUTHOR]

This study solves the radial Schrödinger wave equation (RSWE) with the improved Rosen–Morse (IRM) potential constrained by an electromagnetic field. Energy eigenvalues are derived using the parametric Nikiforov–Uvarov method and Pekeris approximation. The internal partition function, isobaric molar heat capacity formula, and magnetization model are then deduced from the equation governing pure vibrational energy states. These analytical models are applied to several pure substances, specifically Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+) molecules. Numerical approximations of the energy eigenvalues for these molecules closely match their exact values. The isobaric molar heat capacity expression yields mean percentage absolute deviations of 1.6585%, 0.9162%, 1.2193%, and 0.7232% when compared against experimental data for Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+), respectively. These results align well with other heat capacity models in existing literature. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the thermodynamic properties of the charged AdS Gauss–Bonnet black holes and their associations with the Lyapunov exponent. The chaotic features of the black holes and the isobaric heat capacity characterized by the Lyapunov exponent are studied to reveal the thermodynamic stability of the black hole phases. By considering both the timelike and null geodesics, we find that the relationship between the Lyapunov exponent and the Hawking temperature can accurately represent the features of the Small/Large phase transition and even the triple point. We also reveal the properties of the difference in the Lyapunov exponent as an order parameter. It is demonstrated that there is a negative correlation between the Lyapunov exponent and the size of the black hole shadow, which can be used to bridge the thermodynamic properties and the shadow of black holes. [ABSTRACT FROM AUTHOR]

This research aims to evaluate the efficacy of Mouromtseff's numbers in assessing the thermal transfer performance of titanium oxide (TiO2) nanosized dispersions in convective heat transfer through a pipe. New experimental coefficients of convective heat transfer, thermophysical and rheological characterisation are carried out for TiO2-based nanodispersions in an aqueous propylene glycol 30 vol% mixture at various nanoadditive mass loadings (from 0.25 to 2.0 wt%). Different Mouromtseff's number formulations, including the Dittus–Boelter and Simons expressions, were obtained from experimental data of thermophysical properties, enabling concise analyses on the prospective improvement of heat transfer in cooling and heating systems. The morphology, particle size, and crystallinity of the anatase TiO2 nanopowder were confirmed, and the stability of the nanofluids with various surfactants was evaluated, with PSS at a 1:4 mass ratio being optimal. Slight increments in thermal conductivity (up to 1.5%) and density (up to 1.3%) with nanoparticle loading were observed, while isobaric heat capacity presents a decreasing trend (less than 13%). Dynamic viscosity increases with higher nanoadditive concentrations, 8.8% for the 2.0 wt% A-TiO2/PG:W 30:70 + PSS 1:4 nanofluid. The employed Dittus–Boelter and Simons expressions correctly predict a worsening of the convective heat transfer, but the percentages diverge slightly from experimental data. [ABSTRACT FROM AUTHOR]

The total internal partition sum, Qint(T), and the translational partition sum, Qtrans(T), were computed for six isotopologues of NO: 14N16O, 15N16O, 14N18O, 14N17O, 15N18O, 15N17O. These were used to determine the total partition sum, Q(T), and its first and second moments, Q ̃ ′ T and Q ̃ ″ T . The total internal partition sum was computed using term values determined by Qu et al. [Mon. Not. R. Astron. Soc. 504, 5768–5777 (2021)] for 14N16O and those of Wong et al. [Mon. Not. R. Astron. Soc. 470, 882–897, (2017)] for the other isotopologues. These term values are the best available and hence provide the most accurate total internal partition sums and its first and second moments. The uncertainties in Qint(T), its moments, and the resulting thermodynamic functions were determined from the uncertainty in the term values and the uncertainty due to the convergence of the partition sum and its moments. From these quantities, the isobaric heat capacity, Helmholtz energy, entropy, enthalpy, Gibbs function, and the JANAF functions hef and gef, and their uncertainties, were computed on a 1 K grid from 1 to 9000 K. The data are compared with the literature values. The resulting thermodynamic quantities are the most accurate determined from direct summation of Q(T), Q ̃ ′ T , and Q ̃ ″ T . [ABSTRACT FROM AUTHOR]

As part of a series of studies of hydrogen‐atom transfer or tautomerization reactions of imidic acid–amide species, H─O═C─N─⇌O═C─N─H${\rm H\bond O\dbond C\bond N\bond} \rightleftharpoons {\rm O\dbond C\bond N\bond H}$, we report the rate constants for a set of 24 five‐membered cyclic compounds at low, 50–300 K, and high, 500–1500 K, temperatures. These rate constants are for both the high temperature direct reaction and for that mediated by an additional water molecule which facilitates the hydrogen transfer reaction at low temperatures. In the latter case we show that the rate of reaction from a pre‐reaction complex can be rapid at temperatures down to 50 K on a 1 ms timescale and is dominated by quantum mechanical effects as evaluated by small‐curvature and quantised‐reaction‐states tunnelling. In addition, we present thermochemical data such as enthalpies of formation, entropies, isobaric heat capacities and enthalpy functions for these largely unknown species which span a range of compounds from pyrolidinone to oxo‐tetrazoles. [ABSTRACT FROM AUTHOR]

The mechanisms behind the polymer glass transition, though not fully elucidated, have garnered significant attention. The Locally Correlated Lattice (LCL) theory [R. P. White, J. E. Lipson, Macromolecules2016, 49, 3987] provides a novel perspective on free volume and establishes the relationship between polymer glass transition and free volume. In this study, we present a dynamic theoretical model based on the thermodynamic LCL theory, focusing on the kinetic evolution of free volume during polymer glass transition. Our analysis simultaneously examines the segmental diffusion coefficient, dynamic correlation length, free volume, and isobaric heat capacity. The results indicate that, upon reaching a critical temperature, heterogeneous dynamics and singular thermodynamics emerge concurrently. This study establishes a comprehensive correlation between thermodynamic singularities and dynamic inhomogeneities, offering valuable insights into the polymer glass transition process. [ABSTRACT FROM AUTHOR]

Wearable thermoelectric generators have great potential to provide power for smart electronic wearable devices and miniature sensors by harnessing the temperature difference between the human body and the environment. However, the Thomson effect, the Joule effect, and heat conduction can cause a decrease in the temperature difference across the thermoelectric generator during operation. In this paper, phase change materials (PCMs) were employed as the heat sink for the thermoelectric generator, and the COMSOL software 6.1 was utilized to simulate and optimize the power generation processes within the heat sink. The results indicated that with a PCM height of 40 mm, phase transition temperature of 293 K, latent heat of 200 kJ/kg, phase transition temperature interval of 5 K, thermal conductivity of 50 W/(m·K), isobaric heat capacity of 2000 J/(Kg·K), density of 1000 kg/m3, and convective heat transfer coefficient of 10 W/(m·K), the device can maintain a temperature difference of 18–10 K for 1930 s when the thermoelectric leg height is 1.6 mm, and 3760 s when the thermoelectric leg height is 2.7 mm. These results demonstrate the correlation between the device's output performance and the dimensions and performance parameters of the PCM heat sink, thereby validating the feasibility of employing the PCM heat sink and the necessity for systematic investigations. [ABSTRACT FROM AUTHOR]

The isobaric condensed-phase heat capacities of selected pharmaceutical active ingredients (APIs), namely nifedipine (CAS RN: 21829-25-4), griseofulvin (CAS RN: 126-07-8), probucol (CAS RN: 23288-49-5) and 5,5-diphenylhydantoin (CAS RN: 57-41-0), were determined over a wide temperature range starting from 2 K by combination of relaxation (heat pulse) calorimetry, Tian-Calvet calorimetry and power-compensated differential scanning calorimetry. Heat capacity measurements were taken for clearly specified polymorphs, a liquid phase (including subcooled liquid) and a glassy amorphous phase, if feasible. For 5,5-diphenylhydantoin, a heat capacity anomaly was detected in the temperature range 160 to 190 K and interpreted based on additional calorimetric and temperature-variable crystallographic measurements as a sequence of two phase transitions, which are reported for the first time in this work. Based on the determined phase behavior and heat capacity data from near 0 K, standard thermodynamic functions for crystalline and liquid phases were calculated for all APIs studied. This work significantly extends the availability of reliable heat capacity data and related thermodynamic properties for APIs required for modeling their solubility and other applications involving thermodynamic modeling. [ABSTRACT FROM AUTHOR]

The high-pressure and high-temperature thermodynamic properties of rhodium (up to 2000 K and 300 GPa) are presented using the first principle approach within the quasi-harmonic approximation. The thermal Helmholtz free energy includes the contribution of both phonon vibrations and electronic excitations. The performance of three popular exchange-correlation functionals—local density approximation [Perdew et al., Phys. Rev. B 23, 5048 (1981)], Perdew–Burke–Ernzerhof generalized gradient approximation (PBE) [Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)], PBE modified for dense solids [Perdew et al., Phys. Rev. Lett. 100, 136406 (2008)] are shown. The simulated thermal expansion coefficient, isobaric heat capacity, mode-Grüneisen parameter, thermodynamic average Grüneisen parameter, and bulk modulus are compared with the available experimental and theoretical reports. The contribution of thermal electronic excitations to the obtained thermodynamic parameters is significant at low pressure and high temperatures, except in bulk modulus, where it is small. The pressure-dependent elastic constant coefficient (Cij) and the Debye temperature are computed at 0 K. The Pugh ratio calculated from Cij indicates that rhodium undergoes brittle to ductile transitions at an average pressure of 7.45 GPa. [ABSTRACT FROM AUTHOR]

Aiming at the energy supply problem of underwater equipment such as manned deep submarines, submarine base stations, etc., this paper proposes an underwater high-energy laser wireless power transmission system and focuses on analyzing the influence of the steady-state thermal blooming effect on the quality of underwater high-energy laser power transmission. First, the intensity distributions under the influence of the thermal blooming effect are numerically simulated based on the multiple phase-screen method and the fast Fourier transform, considering the changes in the initial beam radius, transmission distance, transmitting power, wavelength, absorption coefficient of the water medium, and isobaric specific heat capacity. Emphatically, transmission efficiency and beam flux contrast are used to characterize the quality of power transmission and then find the suitable laser modes and seawater environment for underwater power transmission. The results indicate that reducing the thermal blooming effect may increase the efficiency of light energy transmission, but it will also decrease the photoelectric conversion efficiency of photovoltaic cells. Therefore, for balancing the energy transfer efficiency and the beam flux contrast, it is necessary to choose appropriate initial laser parameters based on actual underwater environmental parameters. Our study is helpful for the design of the underwater laser wireless power transmission system. [ABSTRACT FROM AUTHOR]

The isobaric heat capacities of phenol and its aqueous solutions with concentrations of 2, 4, and 5.9 wt % were studied using a scanning calorimeter (IT-s-400) at temperatures from 313 to 473 K and pressures of up to 19.6 MPa. The results were compared with the literature data in the given range of state parameters. [ABSTRACT FROM AUTHOR]

This study discusses the transition toward the use of environmentally friendly refrigerants in low-temperature technology. It also considers a new environmentally friendly fourth-generation refrigerant trans‑1,3,3,3-tetrafluoropropene R1234ze(E) as an alternative to the R134a refrigerant common in chillers and heat pumps, as well as the R22 refrigerant in air conditioning systems. A technique has been developed for constructing a unified fundamental equation on the states of liquid and gas for trans‑1,3,3,3-tetrafluoropropene. Around the critical point, the proposed fundamental equation satisfies the requirements of the scale theory for asymmetric systems, and in the region of a rarefied gas, it is reduced to the virial equation of state. Based on this fundamental equation, tables of standard reference data on pressure, density, enthalpy, isobaric and isochoric heat capacities, entropy, heat of vaporization, and sound velocity of trans‑1,3,3,3-tetrafluoropropene in the region of state parameters in the temperature ranges of 169–420 K and pressure of 0.1–100 MPa were calculated. Several statistical characteristics have been calculated, namely, absolute mean deviation, systematic deviation, standard deviation, and root mean square deviation, characterizing the accuracy of the proposed fundamental equation in describing the experimental values of the equilibrium properties obtained in recognized international thermophysical centers. Evidently, the values of these statistical characteristics are significantly lesser than those of the corresponding characteristics of the international fundamental equations of state, provided in the literature, when describing the thermal and caloric experimental data of trans‑1,3,3,3-tetrafluoropropene. The estimated expanded uncertainties of the tabulated data based on the proposed fundamental equation were 0.26% for density, 0.57% for pressure, 1.7% and 1.2% for isochoric and isobaric heat capacities, respectively, and 0.38% for sound velocity. The results suggest that the proposed unified fundamental equation of state adequately conveys the thermodynamic characteristics of trans‑1,3,3,3-tetrafluoropropene over the specified range of temperatures and pressures. [ABSTRACT FROM AUTHOR]

The text is a preface to a special issue of the Journal of Solution Chemistry dedicated to the memory of Professor Jean-Pierre E. Grolier, who passed away in 2022. Professor Grolier made significant contributions to the field of experimental thermodynamics over his 50-year career. His research focused on various topics, including the determination of excess molar enthalpies and heat capacities of liquid mixtures, scanning transitiometry, high-pressure flow techniques, electrolyte solutions, thermophysical properties of polymers, and thermodynamic properties of fluids in confined spaces. He also held various positions in professional organizations and was recognized for his contributions to the field. The special issue aims to honor his scientific legacy by featuring articles from former collaborators and researchers in related fields. [Extracted from the article]

The thermophysical properties of various types of nanofluids are often studied to find more effective working fluids for heat transfer applications. In this paper, the mass density, isobaric heat capacity, thermal conductivity, dynamic viscosity surface tension, and electrical properties of calcium carbonate-ethylene glycol (CaCO 3 -EG) nanofluids were investigated. The samples with mass fractions of 0.01, 0.02, and 0.03 were prepared with a two-step method and studied as well as pure base fluid (ethylene glycol). The measurements were conducted at temperatures between 283.15 and 313.15 K and the obtained results show the impact of CaCO 3  nanoparticles on the thermophysical and electrical properties of ethylene glycol. [ABSTRACT FROM AUTHOR]

Comprehensive and accurate measurements of the speed of sound in liquid water are reported. The measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range from 273.65 K to 368.15 K with pressures up to 100 MPa. The relative expanded ( k = 2 ) uncertainties are 2.1 mK in temperature, 45 parts-per-million (ppm) in pressure, and between 40 ppm and 70 ppm in speed of sound. Furthermore, values for the density and specific isobaric and isochoric heat capacities were derived from the speed of sound data in the measured temperature range up to 100 MPa by the method of thermodynamic integration. Very accurate values for the derived properties were obtained by using density data of Takenaka and Masui (Metrologia 27:165–171, 1990) and isobaric heat capacity data of Osborne et al. (J Res Natl Bur Stand 23:197, 1939) at ambient pressure as initial values in combination with an accurate correlation of our speed of sound. The relative expanded ( k = 2 ) uncertainties of the derived properties are 2 ppm in density, 0.11% in isobaric heat capacity, and 0.12% in isochoric heat capacity. The experimental speeds of sound and derived properties are compared with experimental data of other authors from the literature, the IAPWS-95 (International Association of the Properties of Water and Steam) formulation for the thermodynamic properties of water, and a recent equation of state for supercooled water. [ABSTRACT FROM AUTHOR]

The article provides a methodology for designing heat transfer in mechanically agitated vessels, focusing on agitated heat transfer principles, equations, and calculations for vessels with turbine agitators. Topics include solving simultaneous heat transfer equations, calculating overall heat transfer coefficients, and exploring heat transfer surfaces like jackets and helical coils.

As shown, the dimensional dependence of the thermodynamic characteristics of nanocrystals is due to the dimensional quantization of vibrational modes of nanocrystals and leads to the dimensional caloric effect in nanocrystals. This effect manifests itself in the excess pressure of the phonon gas, an increase in the heat capacity, a decrease in the melting temperature, and heat absorption by nanocrystals as their size decreases. The consequence of these size-dependent effects in nanocrystals is the non-additivity of energy, which can be realized in the reverse transfer of heat from a cold body to a hot one. [ABSTRACT FROM AUTHOR]

In the last years, a lot of research is committed to developing new heat transfer fluids for medium to high temperatures applications. This experimental analysis is dedicated to a less studied fluid, PEG 400 enhanced with titanium oxide nanoparticles, and started with suspensions manufacturing, morphology analysis and a strong discussion on viscosity, rheological behavior and isobaric heat capacity. Precisely, five suspensions of up to 2.5 %wt. TiO2 were analyzed through the entire experimental in terms of their behavior at ambient temperature and heating. Plus, viscosity was checked for possible hysteresis and the experimental revealed that this is almost absent for these nanocolloids, which is favorable for heat transfer applications, especially in heat exchange. The rheological tests revealed a non-Newtonian comportment for all of the samples, comportment that is more obvious when nanoparticles concentration increases. In terms of viscosity outputs, a normal fluidic behavior was noticed at heating, while the viscosity upsurges between 8 and 36 %, depending on nanoparticle concentration. Isobaric heat capacity tests demonstrated a decrease of up to 6.3 % for higher loaded nanocolloids and a relatively small variation with temperature, which is, somehow, in line with state of the art. As a conclusion, it may affirm that nanocolloids based on PEG 400 and oxides can be a good alternative for heat exchange applications.

Thermodynamic properties of polycrystalline powders of ruthenium dichalcogenides have been studied using calorimetric isobaric heat capacity measurements in a wide temperature range. The adiabatic and differential scanning calorimetry data for ruthenium disulfide and ruthenium diselenide have been used to determine standard thermodynamic functions (heat capacity, entropy, enthalpy increment, and reduced Gibbs energy) of these compounds in the range 10–965 K. At 298.15 K, the functions of RuS2 are as follows: = 60.82 ± 0.12 J/(K mol), S° = 56.05 ± 0.11 J/(K mol), Н°(298.15 K) − Н°(0) = 9.75 ± 0.02 kJ/mol, and Ф° = 23.34 ± 0.05 J/(K mol). For RuSe2, we have obtained = 69.96 ± 0.14 J/(K mol), S° = 80.62 ± 0.16 J/(K mol), Н°(298.15 K) − Н°(0) = 13.05 ± 0.03 kJ/mol, and Ф° = 36.85 ± 0.08 J/(K mol). The data obtained above 298 K have been used to determine empirical coefficients of the Maier–Kelley and Khodakovsky equations. The absolute entropies obtained in this study for the ruthenium dichalcogenides, in combination with literature data, have made it possible to evaluate the Gibbs energy of formation of RuS2(cr) and RuSe2(cr) at 298.15 K. [ABSTRACT FROM AUTHOR]

The kinetics of the tautomerization of thio‐imidic acids RC(SH)NH were determined at low (50–300 K) and high (500–1500 K) temperatures as R was varied to encompass mono‐ and diatomic species H, F, HO, NC, CN through H2N, HC(O), HC(S), HC≡ C, H3C, F3C, HOCH2, H2C=CH, CH3C(O), H2NCH2 and including ethyl, isopropyl and phenyl groups. The presence of a labile H‐atom on the R‐group can give rise to an alternative reaction, as in, H3CC(SH)NH → CH2=C(SH)NH2 but these encounter much higher barriers. At the lowest temperatures there is over a million‐fold difference in the rate constants for the fastest, R = H2N, and slowest, R = F, reaction with quantum mechanical tunneling playing a dominant role which is dealt with by canonical transition state and small curvature tunneling theory. The tautomerization of similar imidic acids proceeds at much slower rates due to higher energy barriers to reaction. Additionally basic thermochemical data such as formation enthalpy, entropy, isobaric heat capacity and an enthalpy function are provided for all the species which may be useful training sets for machine‐learning/AI purposes. [ABSTRACT FROM AUTHOR]

A fundamental equation of state expressed explicitly in the Helmholtz energy is presented for R-1224yd(Z), an environmentally friendly refrigerant for centrifugal chillers, high-temperature heat pumps, and organic Rankine cycles. The equation of state is based on consistent experimental data for the critical parameters, vapor pressures, saturated liquid and vapor densities, (p , ρ , T) behavior, vapor-phase sound speeds, liquid-phase sound speeds, and ideal-gas isobaric heat capacities. The equation is valid at temperatures from the triple-point temperature (157.8 K) to 473 K and pressures up to 35 MPa. In the valid range, expected relative uncertainties ( k = 2 ) of the equation are 0.04 % for vapor pressures, 0.1 % for saturated liquid densities, 2 % for saturated vapor densities, 0.05 % for liquid densities, 0.3 % for vapor densities, 0.02 % for vapor-phase sound speeds, and 0.04 % for liquid-phase sound speeds, except in the critical region, where more significant uncertainties of up to 2 % are sometimes observed in densities. The equation exhibits reasonable behavior in the critical and extrapolated regions; this is demonstrated by several plots of derived properties over wide ranges of temperature and pressure. [ABSTRACT FROM AUTHOR]

A cubic equation of state (EOS) always contains a quadratic term, or a quadratic term and a cubic term, where the quadratic term may contain temperature dependent parameters(s). Therefore, the discriminant (Δ) of quadratic term may change sign in the variation of temperature. If so, the functional forms of the residual thermal properties (such as residual internal energy, enthalpy, entropy, isochoric and isobaric heat capacity) derived from the EOS will change accordingly. When Δ = 0, the quadratic term degenerates into a perfect square of volume, which can be used to derive fugacity coefficient, residual Gibbs and Helmholtz free energy, but cannot give correct residual thermal properties. To solve this problem, non-degenerate transformation of quadratic fraction must be used. When Δ < 0, the residual thermal properties are derived by the method of undetermined coefficients or integration by parts. For the sake of generality, the general form of cubic equations of state is used to derive residual thermal properties according to the sign of Δ. The derivation starts from residual internal energy and fugacity coefficient, and then extends to other residual properties. These results and approaches can be used in the efforts to improve the accuracy of the cubic EOS, or to extend cubic EOS to the supercritical region that is very far from the critical points of pure fluids. [ABSTRACT FROM AUTHOR]

The processes occurring during heating of a stoichiometric mixture of lanthanum, samarium, magnesium, and aluminum hydroxides synthesized by the reverse precipitation method have been studied by DTA/TG and X-ray powder diffraction methods. The conditions for the synthesis of single-phase LaMgAl11O19 and SmMgAl11O19 samples of the magnetoplumbite structure type have been determined, and the isobaric heat capacity has been measured in the temperature range 317–1817 K, showing the absence of structural transformations in this range. [ABSTRACT FROM AUTHOR]

• TiO 2 suspended in PEG 400 fluids properties are debated. • Viscosity decreases with temperature increase and increases with TiO 2 addition. • Isobaric heat capacity of samples declines when nanoparticles are added to PEG 400. • Correlations are proposed for PEG 400 + TiO 2 fluids, in terms of viscosity and isobaric heat capacity. In the last years, a lot of research is committed to developing new heat transfer fluids for medium to high temperatures applications. This experimental analysis is dedicated to a less studied fluid, PEG 400 enhanced with titanium oxide nanoparticles, and started with suspensions manufacturing, morphology analysis and a strong discussion on viscosity, rheological behavior and isobaric heat capacity. Precisely, five suspensions of up to 2.5 %wt. TiO 2 were analyzed through the entire experimental in terms of their behavior at ambient temperature and heating. Plus, viscosity was checked for possible hysteresis and the experimental revealed that this is almost absent for these nanocolloids, which is favorable for heat transfer applications, especially in heat exchange. The rheological tests revealed a non-Newtonian comportment for all of the samples, comportment that is more obvious when nanoparticles concentration increases. In terms of viscosity outputs, a normal fluidic behavior was noticed at heating, while the viscosity upsurges between 8 and 36 %, depending on nanoparticle concentration. Isobaric heat capacity tests demonstrated a decrease of up to 6.3 % for higher loaded nanocolloids and a relatively small variation with temperature, which is, somehow, in line with state of the art. As a conclusion, it may affirm that nanocolloids based on PEG 400 and oxides can be a good alternative for heat exchange applications. [ABSTRACT FROM AUTHOR]

The high-density amorphous phases (HDAs) of bimetallic zeolitic imidazolate frameworks (Zn/Co-ZIF-4) were prepared. The temperature dependence of the isobaric heat capacity (Cp) of ZIF-4 HDAs was measured to determine the glass transition temperature (Tg) of HDAs. The Tg non-linearly decreases with the molar ratio R, where R is Co/(Co + Zn), indicating the presence of a mixed-metal node effect. This effect arises from the non-linear increase of the degree of configurational freedom in the HDA as R increases. The degree of configurational freedom is inversely correlated with the network connectivity, which is, in turn, affected by variations in the MN4 (M: Zn or Co; N: nitrogen) tetrahedral symmetry in the ZIF-4 HDA. Overall, this work offers valuable insights into the glass transition of metal–organic frameworks. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of crystalline ruthenium ditelluride (RuTe2) and its thermodynamic properties in the range from 10 to 965 K, evaluated from its isobaric heat capacity Cp determined using calorimetry. At low temperatures, between 6.86 and 335.11 K, the heat capacity of the synthesized material—pure, free of impurities and foreign phases—was determined by adiabatic calorimetry. In the range 315.3–965.3 K, Cp was determined by differential scanning calorimetry. The data obtained above 298 K have been used to determine empirical coefficients of the Maier–Kelley and Khodakovsky equations. In the range 10–965 K, we have evaluated the standard thermodynamic functions: heat capacity, entropy, enthalpy increment, and reduced Gibbs energy. At 298.15 K, we have obtained = 72.43 ± 0.14 J/(K mol), S° = 94.94 ± 0.19 J/(K mol), Н°(298.15 K) − Н°(0) = 14.60 ± 0.03 kJ/mol, and Ф° = 45.97 ± 0.09 J/(K mol). Using the absolute entropy determined by us and data in the literature and handbooks, we have estimated the standard Gibbs energy of formation of RuTe2: ΔfG°(RuTe2, cr, 298.15) = −130.5 ± 2.9 kJ/mol. [ABSTRACT FROM AUTHOR]

• The molecular dynamics simulation have been used to investigate the condensation process, thermophysical and structural properties of nine binary blend of R1234ze+R134a. • Condensation temperature and condensation pressure can affect the condensation rate of refrigerants. • Condensation time decreased with increasing R1234ze(E) mass ratio. • The molecular structure remained un-affective during the condensation process of binary blends. Environmental concerns demand prioritizing the development of eco-friendly refrigerants and prompting the replacement of conventional working fluids. The HFCs (hydrofluorocarbon) will be banned soon, and HFOs (hydrofluoroolefin) have been indicated as an alternative. In this study, numerous blends were attained by mixing two refrigerants, R-1234ze(E) and R-134a. Few blends are proposed as substitutes for high Global Warming Potential (GWP) fluids and are employed in refrigeration systems. The homogeneous condensation and thermophysical properties of nine binary blends of R-1234ze(E) + R-134a by varying composition with increment and decrement, respectively of 10% for each in a sequence were investigated using a molecular dynamics simulations scheme. The density, isobaric heat capacity, mean square displacement, internal potential energy and radial distribution function were investigated at constant pressure and different condensation temperatures (273.15 K to 328.15 K). The present study aims to check how the mass ratio of different refrigerants can affect mentioned properties. The current outcomes are compared, analyzed and discussed with earlier available simulation data for pure and mixtures of refrigerants and along with REFPROP data. The computed results show that Blend 4, with a 60.0+40.0% mass ratio composition and R-450A, has similar condensation behavior and thermophysical properties. The properties of Blend 5 with a composition 50.0+50.0% mass ratio are nearly equal to Blend 4 and R-450A. The R-450A has a good inclusive performance as a pure alternative refrigerant. The physical properties of pure R-1234ze(E), R-134a and its nine binary blends were investigated and these results may be helpful for new HFO refrigerants based on these blends. [ABSTRACT FROM AUTHOR]

An empirical fundamental equation of state in terms of the Helmholtz energy for tetrahydrofuran is presented. In the validity range from the triple-point temperature up to 550 K and pressures up to 600 MPa, the equation of state enables the calculation of all thermodynamic properties in the liquid, vapor, and super-critical regions including saturation states. Based on an extensive literature review, experimental data are represented within their experimental uncertainty. In the homogeneous liquid phase at atmospheric pressure, the uncertainty in density is 0.015 %, speed of sound is represented with an uncertainty of 0.03 %, and isobaric heat capacity has an uncertainty of 0.4 %. Isobaric heat capacities in the homogeneous vapor phase are described with an uncertainty of 0.2 %. Higher uncertainties occur above atmospheric pressure for all homogeneous properties. Depending on the temperature range, vapor pressure can be calculated with an uncertainty from 0.02 % to 3 %. The extrapolation behavior is evaluated, showing reasonable extrapolation behavior towards extreme conditions. [ABSTRACT FROM AUTHOR]

The suggestion that the paper by Naef and Acree is the first one with the capability to treat "any molecule under the sun" is simply totally incorrect. In Ref. [[7]] (Neaf and Acree), reference to GC methods are only the previous publications by Naef and Acree. 10.3390/molecules25051147 7 Naef R., Acree W.E. Jr. Calculation of the Vapour Pressure of Organic Molecules by Means of a Group-Additivity Method and their Resultant Gibbs Free Energy and Entropy of Vaporization at 298.15 K. References 1 Naef R., Acree W.E. Jr. Revision and Extension of a Generally Applicable Group-Additivity Method for the Calculation of the Standard Heat of Combustion and Formation of Organic Molecules. [Extracted from the article]

Ionic liquids are deliberated, lately, as the perfect candidate for new heat transfer fluids. This article aims to debate on several experimental outcomes in terms of viscosity and isobaric heat capacity for [C4mim][BF4] ionic liquid and several suspensions of Al2O3 nanoparticles (up to 2.5 mass%) in [C4mim][BF4]. The methodological approach involved the suspensions preparation, isobaric heat capacity and viscosity tests, as well as discussing the outcomes. Experimental data were acquired at 293.15 K and after several heating–cooling cycles, while the results outlined that the ionic liquid has a Newtonian behavior, while the suspensions with alumina have non-Newtonian behavior at low shear rates, while at upper shear rates the flow is changed into Newtonian. Also, the suspensions viscosity was found discreetly higher if compared with the base ionic liquid. A novelty is the study of a possible hysteresis in terms of viscosity, while the successive heating–cooling tests revealed a good stability. The isobaric heat capacity tests revealed a moderate decrease when nanoparticles are added. Concluding, this experimental may shed some light on both [C4mim][BF4] and its ionanofluids with Al2O3 nanoparticles; however, it is only a step forward so as to gain a full synopsis on these new fluids. [ABSTRACT FROM AUTHOR]

We investigate the temperature dependence of thermodynamic (density and isobaric heat capacity), dynamical (self-diffusion coefficient and shear viscosity), and dielectric properties of several water models, such as the commonly employed TIP3P water model, the well-established four-point water model TIP4P-2005, and the recently developed four-point water model TIP4P-D. We focus on the temperature range of interest for the field of computational biophysics and soft matter (280–350 K). The four-point water models lead to a spectacularly improved agreement with experimental data, strongly suggesting that the use of more modern parameterizations should be favored compared to the more traditional TIP3P for modeling temperature-dependent phenomena in biomolecular systems. [ABSTRACT FROM AUTHOR]

We present an ab initio study of the temperature dependent elastic constants of boron arsenide, a semiconductor that exhibits ultra-high thermal conductivity and is under investigation for thermal management in electronics. We test the consistency of our predictions by computing the temperature dependent sound velocity of the longitudinal acoustic mode along the [ 111 ] direction and comparing with experiments. Furthermore, as a by-product, we present the room temperature phonon dispersions and the temperature dependent thermal expansion, isobaric heat capacity, and average Grüneisen parameter compared with the most updated experiments and previous calculations when available. Finally, we present the theoretical estimate of the temperature dependent mean square atomic displacements. [ABSTRACT FROM AUTHOR]

The search for new eutectic solvents for different applications (extraction, drug formulation, chemical reactions, etc.) is booming thanks to their high solubility capacity and low toxicity. However, it is necessary to carry out a comprehensive physicochemical characterization of these mixtures to understand the molecular behavior at different experimental conditions. In this study, three deep eutectic solvents (DESs) formed by glycerol and xylitol, fructose and sorbitol and water in the molar ratio 1:2:3 were prepared and several physicochemical properties (refractive index, density, surface tension, viscosity, speed of sound, isobaric heat capacity and isentropic compressibility) were measured and analyzed in the 278.15–338.15 K temperature range. The results indicate a linear dependence with temperature for the following properties: surface tension, refractive index, density and isobaric molar heat capacity while viscosity values have been fitted to the Vogel–Fulcher–Tammann equation. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of crystalline platinum ditelluride, PtTe2, a synthetic analog of the mineral moncheite, and its thermodynamic properties. Using the isobaric heat capacity of PtTe2 determined in the range 2–305 K by the relaxation and adiabatic calorimetry methods, we have evaluated its standard thermodynamic functions: entropy, enthalpy increment, and reduced Gibbs energy. The following parameters have been obtained for PtTe2 at 298.15 K: = 75.11 ± 0.15 J/(K mol), S° = 121.5 ± 0.2 J/(K mol), Н°(298.15 K) − Н°(0) = 16.69 ± 0.03 kJ/mol, and Ф° = 65.55 ± 0.13 J/(K mol). Using data in the literature and handbooks, we have estimated the standard Gibbs energy of formation of PtTe2: ΔfG°(PtTe2, cr, 298.15) = –75.4 ± 0.8 kJ/mol. Fractal analysis of the heat capacity data indicates that PtTe2 has a layered structure and that its Debye temperature is 250 K. [ABSTRACT FROM AUTHOR]

The relevance of research into the thermophysical properties of lead is associated with the implementation of a BREST-300 reactor project. The enthalpy of solid and liquid lead in the range of 432–1327 K was measured by the mixing method using a massive isothermal calorimeter. The enthalpy of melting was determined. Approximation equations for the temperature dependence of enthalpy in the range of 298.15–1325 K were obtained to determine the isobaric heat capacity. The existence of a heat capacity minimum for liquid lead in the region of 830 K was established. An analysis of existing recommended and experimental data on the caloric properties of lead was performed. The need for new measurements of the enthalpy and heat capacity of a melt at temperatures above 1050 K is substantiated. [ABSTRACT FROM AUTHOR]

Titanium-manganites of LaLi2TiMnO6 and LaNa2TiMnO6 were synthesized by the methods of ceramic technology from the oxides of lanthanum, titanium (IV), manganese (III), and the carbonates of lithium and sodium. The types of their syngony and the parameters of their gratings were determined radiographically. The isobaric heat capacities of titanium-manganites were measured with experimental calorimetry in the range of 298.15–673 K. It was found that on the dependence curve of heat capacity versus temperature of C°p~f(T), for LaLi2TiMnO6 at 348 K and 598 K, and LaNa2TiMnO6 at 348 K, there are abnormal jumps in heat capacity, probably related to phase transitions of the second kind. Taking into account the temperatures of the phase transitions, the equations of the temperature dependence of the heat capacity of titanium-manganites were derived. Their standard entropies were calculated by the ion increments method. Temperature dependences of the thermodynamic functions of S°(T), H°(T)-H°(298.15), and Φxx(T) were calculated using the experimental data on heat capacities and the calculated values of the standard entropies. The standard heat capacities of the studied compounds were calculated by the independent methods of ion increments and Debye, the values of which were in satisfactory agreement with the experimental data. The standard enthalpy of the formation of LaLi2TiMnO6 and LaNa2TiMnO6 was calculated according to the methodology developed by the authors. The conducted electrophysical studies determined the nature of the second-order phase transition and the semiconductor features of their conductivity. Thus, all the above-mentioned data on the experimental and calculated studies of the temperature dependence of heat capacity, the thermodynamic functions to determine a standard enthalpy of formation of LaLi2TiMnO6 and LaNa2TiMnO6, and the investigation of their electrical properties are absolutely new, and they have no analogues. [ABSTRACT FROM AUTHOR]

Accurate determination of the thermophysical properties of hydrogen is a crucial issue in hydrogen system design. By developing computational programs, a statistical thermodynamic model based on fundamental equations of state was implemented to determine hydrogen's thermophysical properties, including the ortho-hydrogen fraction in equilibrium hydrogen, para-ortho hydrogen conversion heat, isobaric heat capacities and enthalpies. The deviations of calculated para-hydrogen enthalpies from REFPROP data were within 2.22%, ranging from 20 K to 300 K at 0.1 MPa, and within 2.32% between 100 K and 1500 K at pressures from 0.1 MPa to 20 MPa. To quantitatively assess the convenience of the statistical thermodynamic method, the running speeds of programs with different methods for determining hydrogen's thermophysical properties were compared. The time required for statistical thermodynamic calculation was 7.95% that required for treading REFPROP data when the performance of the variable density multilayer insulation combined with a one vapor-cooled shield and para-ortho hydrogen conversion was calculated. The programs developed based on the statistical thermodynamic method can be used to determine the thermophysical properties of hydrogen or other fluids. [ABSTRACT FROM AUTHOR]

The total partition sum, Q(T), and its first and second moments, Q′(T) and Q″(T), were determined in terms of the total internal partition sum, Qint(T), and the translational partition sum, Qtrans(T), for 14N2, 14N15N, and 15N2. The total internal partition sum was computed using term values determined using the molecular constants of Le Roy et al. [J. Chem. Phys. 125, 164310 (2006)] for the ground electronic state and molecular constants for the first eight excited electronic states. The work of Le Roy et al. provides the best term values available and, hence, the most accurate total internal partition sums and their first and second moments. The convergence of Qint(T) and its moments were carefully studied and resulted in values with small uncertainty to 9000 K. From these quantities, the isobaric heat capacity, the Helmholtz energy, the entropy, the enthalpy, the Gibbs function, and the JANAF functions S0, hef, and gef, were computed on a 1 K grid from 1 to 9000 K. The resulting thermodynamic quantities are the most accurately determined from the direct summation of Q(T), Q′(T) and Q″(T). These data are compared with literature values. [ABSTRACT FROM AUTHOR]

For mercury dibromide HgBr2, a promising component of the working mixture of gas-discharge exciplex sources of coherent (lasers) and spontaneous (exciplex lamps) radiation, as well as a promising nonlinear optical crystal for the infrared radiation process, thermodynamic and thermochemical properties in the temperature range 173-512 K were investigated. The established basic thermodynamic (isobaric heat capacity Cp, total entropy S, enthalpy H and Gibbs energy G) and thermochemical (enthalpy ΔHf and Gibbs energy ΔGf of formation) functions of HgBr2 were compared with the known literature data at 298514 K. The obtained results differed from the literature within 1-2% (for Cp), 0.1-0.2% (for S, H and G) and 0.1-0.6% (for ΔHf and ΔGf). The experimental data, combined with semi-empirical approaches and ab initio calculations taken from the literature, were used to estimate the previously unknown additional thermodynamic and thermophysical properties of HgBr2: isochoric heat capacity CV, Debye temperature θD, volume thermal expansion αV, isothermal compressibility βT (isothermal bulk modulus BT = 1/βT), Gruneisen constant γG, phonon longitudinal vl, transverse vs, average ... velocities and phonon thermal conductivity k. In the present work, it was found that crystalline mercury dibromide expands strongly upon heating and has a low phonon thermal conductivity. [ABSTRACT FROM AUTHOR]

This work presents a fundamental equation of state for the thermodynamic properties of R-1336mzz(E). The equation of state is expressed explicitly in the Helmholtz energy with temperature and density as the independent variables, and is based on consistent experimental datasets, including the critical parameters, vapor pressure, saturated liquid and vapor densities, (p , ρ , T) behavior, vapor phase sound speed, and ideal-gas isobaric heat capacity. The equation of state is valid for temperatures from 200.15 K to 410 K and pressures up to 5.7 MPa. In this range, expected relative uncertainties at the 95 % confidence interval ( k = 2 ) are 0.1 % for vapor pressures, 1 % for saturated liquid densities, 1 % for saturated vapor densities, 0.15 % for liquid densities, 0.5 % for vapor densities, and 0.05 % for vapor phase sound speeds, except in the critical region where larger uncertainties of up to 2 % are sometimes observed in densities. The equation exhibits reasonable behavior in the critical and extrapolated regions; this is demonstrated by several plots of derived properties over wide ranges of temperature and pressure. Through the use of the new equation of state, this work also formulates an extended corresponding states (ECS) model for the viscosity and thermal conductivity of R-1336mzz(E) to represent recent experimental data for these properties mostly within their uncertainties. [ABSTRACT FROM AUTHOR]

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The possibility of constructing the equation of state of a crystalline substance based on a linear combination of the Planck–Einstein functions is shown using the example of corundum α-Al2O3. Two versions of the corundum equation of state are obtained on the basis of functions F(V,T) and G(P,T) as a result of the self-consistency of the heat capacity values, the enthalpy increment, PVT data, the coefficient of thermal expansion, and the adiabatic modulus of elasticity. Both equations provide an acceptable description of the above properties in a wide range of variables (up to a pressure of 165 GPa and a temperature of 2250 K). [ABSTRACT FROM AUTHOR]