Enthalpy Difference Research Articles

Thermophysical parameters governing the glass formation and crystallization of CuZr

Cu-Zr is one of the best binary metallic glass formers. Here, new data on the enthalpy and specific heat difference between undercooled melt and crystal phases are provided for the equiatomic composition CuZr. Together with a comprehensive collection of literature data on the heat of crystallization and fusion, on the viscosity and crystal growth rate, the parameters needed for the application of the Classical Nucleation Theory are assessed. The TTT and CCT curves for crystallization are computed allowing the determination of the crystal-liquid interfacial energy by fitting the critical cooling rate for bulk glass formation.The glass forming tendency of CuZr is discussed pointing to the role of the high interfacial energy and the sluggish interdiffusion in the undercooled melt.

Evaluation of correlations for mass flow rate of refrigerant through electronic expansion valve in air—water heat pump system using R32

To measure mass flow rate of R32 through EEVs under real operating conditions, a commercially available air-water heat pump (AWHP) system was operated in as wide a range as possible. Measurements showed that the effect of oil circulation on the refrigerant mass flow rate of the test system was negligible. To examine whether they were able to predict refrigerant mass flow rate of R32 in a real operating heat pump systems, previous empirical correlations available in the open literature were compared against these measured data. Previous empirical correlations, except for those of Park et al. (2007), showed poor agreement with the present experimental data, with mean absolute percentage error (MAPE) from 9.1% to 334.5% for EEV#1 (D: 2.40 mm) and from 24.1% to 122.2% for EEV#2 (D: 1.65 mm). These large differences were caused by differences in internal geometry of flow passage and operating conditions due to different refrigerants. A new empirical correlation was developed considering these aspects. The valve opening ratio was considered in terms of the valve flow coefficient variation. The thermodynamic state of refrigerant at the EEV inlet was represented by the enthalpy difference, so as to avoid discontinuity of the mathematical expression at the saturated liquid point. The new correlation showed good agreement with mass flow rate measured through both EEVs, with MAPE values of 9.3% and 14.5% for EEV#1 (D: 2.40 mm) and EEV#2 (D: 1.65 mm), respectively.

Cu3As: Uncommon Crystallographic Features, Low-Temperature Phase Transitions, Thermodynamic and Physical Properties

The formation and crystal structure of the binary Cu3As phase have been re-investigated. Some physical properties were then measured on both single crystal and polycrystalline bulk. Cu3As melts congruently at 835 °C. At room temperature (RT), this compound has been found to crystallize in the hexagonal Cu3P prototype (hP24, P63cm) with lattice parameters: a = 7.1393(1) Å and c = 7.3113(1) Å, rather than in the anti HoH3-type (hP24, P-3c1) as indicated in literature. A small compositional range of 74.0-75.5 at.% Cu (26.0-24.5 at.% As) was found for samples synthesized at 300 and 400 °C; a corresponding slight understoichiometry is found in one out of the four Cu atomic sites, leading to the final refined composition Cu2.882(1)As. The present results disprove a change in the crystal structure above RT actually reported in the phase diagram (from γ' to γ on heating). Instead, below RT, at T = 243 K (-30 °C), a first-order structural transition to a trigonal low-temperature superstructure, LT-Cu3-xAs (hP72, P-3c1) has been found. The LT polymorph is metrically related to the RT one, having the c lattice parameter three times larger: a = 7.110(2) Å and c = 21.879(4) Å. Both the high- and low-temperature polymorphs are characterized by the presence of a tridimensional (3D) uncommon and rigid Cu sublattice of the lonsdaleite type (Cu atoms tetrahedrally bonded), which remains almost unaffected by the structural change(s), and characteristic layers of triangular 'Cu3As'-units (each hosting one As atom at the center, interconnected each other by sharing the three vertices). The first-order transition is then followed by an additional structural change when lowering the temperature, which induces doubling of also the lattice parameter a. Differential scanning calorimetry nicely detects the first low-temperature structural change occurring at T = 243 K, with an associated enthalpy difference, ΔH(TR), of approximately 2 J/g (0.53 kJ/mol). Low-temperature electrical resistivity shows a typical metallic behavior; clear anomalies are detected in correspondence to the solid-state transformations. The Seebeck coefficient, measured as a function of temperature, highlights a conduction of n-type. The temperature dependence of the magnetic susceptibility displays an overall constant diamagnetic response.

Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake

Recently we have shown that thin (33 to 55 nm) oxide films on tungsten (W) prevent deuterium (D) uptake from a low-temperature plasma (5 eV/D; 370 K; 1.4 × 1024D/m2) into metallic W. Here we continue this investigation with higher D fluence up to 2.3 × 1025D/m2 and, additionally, with higher D energies up to 38 eV/D or a higher sample temperature of 500 K. We investigate the reduction mechanism of the oxide and determine under which conditions the permeation barrier effect for D breaks down. We show that during prolonged plasma exposure at 5 eV/D and 370 K, the W-enriched zone that forms at the surface of the oxide stops growing and continues to protect the oxide beneath it against further reduction. For a fluence of 1.6 × 1025D/m2, an originally 55 nm thick oxide film reduces D uptake into the metal by 99%. D enters the metal solely by small cracks in the oxide that form during reduction by the plasma. For higher temperature or D energies, the reduction becomes stronger and more inhomogeneous. D uptake into the metal increases proportional to the area of oxide/metal interface on which the oxide is reduced. The new experiments confirm our previous assumption that D uptake into W is blocked due to the difference in enthalpy of solution of D in W oxide and metallic W. D can only enter the metal once the oxide at the interface is sufficiently reduced. Based on the obtained oxide reduction rates, we made a first tentative estimate of the relevance of naturally occurring W oxide films for D uptake in the plasma-facing components of a fusion reactor. We found that the natural oxide will have none or only a very minor effect in this case.

A Physical Basis for Kinetic Compensation.

Kinetic compensation is a strong, positive correlation between the Arrhenius activation energy E and the frequency factor A for a reaction between the same reactants under similar experimental conditions or similar reactants under the same conditions, even though these parameters are supposed to be independent. The kinetic compensation effect (KCE) is demonstrated by a linear relationship between ln[A] and E/R in the eponymous Constable plot and has been the subject of more than 50 000 publications over the past 100 years, with no consensus opinion about the cause of this effect. In this paper, it is suggested that the linear relationship between ln[A] and E is the result of a real or spurious path dependence of the reaction history between the initial state of the pure reactant(s) and the final state of the pure product(s) having standard enthalpy and entropy differences, ΔH° and ΔS°, respectively. The single-step rate law approximation of a reversible reaction leads to T0 = H°/ΔS° as the dynamic thermal (thermodynamic) equilibrium temperature and 1/T0 = (ln[A̅/k0])/(E̅/R) as the slope of a Constable/KCE plot or the crossover temperature of Arrhenius lines in an isokinetic relationship (IKR), where A̅ and E̅ are mean values for the ensemble of compensating {Ei, Ai} pairs and k0 is a constant that accounts for the path dependence of the reaction history and reconciles the KCE with the IKR. This proposed physical basis for the KCE and IKR is supported by qualitative agreement between ΔH° and ΔS° calculated from the statistics of compensating {Ei, Ai} pairs in the literature, and the difference in the standard enthalpies and entropies of formation of the products and reactants for thermal decomposition of organic peroxides, calcium carbonate, and poly(methyl methacrylate).

Experimental investigation on abnormal heat transfer behaviors of hydrocarbon fuel under supercritical condition in a minichannel

The heat transfer characteristics of hydrocarbons in minichannels were studied experimentally, with the heat transfer process divided into four stages: normal heat transfer, heat transfer enhancement, heat transfer weakened, and heat transfer recovery. The onset of heat transfer weakened (OHW) in the process was considered, and the corresponding heat flux (qOHW) was defined. The results show that qOHW is related to the inlet enthalpy, Reynolds number, and working pressure. A dimensional prediction formula for the qOHW was proposed based on the supercritical boiling number, ratio of enthalpy difference to enthalpy at pseudo-critical temperature, Reynolds number, and dimensionless pressure. The average relative deviation of the correlation was 2.01% compared with the experimental results. This study will contribute to the thermal research on supercritical fluids in a minichannel.

Experimental investigation on the feasibility of a solution regenerator unit using freeze concentration for heat source tower heat pump system

Freeze concentration, which is often used in water treatment and the food industry, has a good regeneration effect and is easy for latent heat utilization. Therefore, a solution regenerator unit using freeze concentration with a heat pump system (SRFCHP) is proposed in this paper. In winter, SRFCHP can achieve weak antifreeze solution concentration, and the heat capacity of frozen phase transition is used to raise the supply water temperature. To investigate the performance of the SRFCHP system, a test was built in the enthalpy difference laboratory. Results shown that the SRFCHP system was able to regenerate the dilute solution from 13 % to 15 % in five regeneration cycle cycles. Around 34.5 % of ice production was able to be separated and the average loss mass of solute was about 0.95 kg per test in the regeneration cycle. Moreover, the SRFCHP system has a better performance on energy efficiency. About 62.5 % of total heat capacity had been recovered effectively. The solute recovery rate was 69.1 %. The coefficient of performance of refrigeration efficiency and heat recovery efficiency were 2.01 and 3.01, respectively. The specific ice production rate was 11.03 kg/kWh. These results demonstrate that the proposed system can be used in frosting regions to regenerate the dilution liquid.

An Experimental Study of the Applicability of the Outdoor Air Enthalpy Difference Method for Air Source Heat Pumps in Operation through In Situ Measurements

This study aimed to evaluate the applicability of the outdoor air enthalpy difference method for air source heat pumps (ASHP) in operation through quantitative analysis using field tests. In this context, field measurements were performed on a single ASHP, and the results were compared with other in situ measurement methods. The main results are as follows. The analysis of the distribution of the discharge temperature of the outdoor unit suggested that the temperature between the hub and tip on the outlet of the outdoor unit can represent the discharge temperature, enabling further simplification of measurement procedures. The mean error of the average cooling capacity using the outdoor air enthalpy difference method was 8% compared to that of the in situ refrigerant enthalpy difference method. In summary, the in situ outdoor unit air enthalpy difference method may require additional measurements to increase reliability, but considering the advantage of relatively easy measurement, it is considered suitable for short-term in situ diagnosis of ASHP performance.

COGITO: A Coarse-Grained Force Field for the Simulation of Macroscopic Properties of Triacylglycerides.

The use of molecular dynamics simulations is becoming ever more widespread; however, the application of this to pure triacylglyceride (TAG) systems is not. In this study, we are presenting the development, and validation, of a new force field (FF), which we have called the COarse-Grained Interchangeable Triacylglyceride-Optimized FF. The FF has been developed using both a bottom-up and top-down approach for different parameters, with the non-bonded parameters being optimized using a Bayesian optimization method. While the FF was developed using monounsaturated TAGs, results show that it is also suitable for fully saturated TAGs. Description of molecules which were not used during the development of the FF is carried out simply by interchanging the bead in the molecule topologies. Results show that the FF can reproduce the macroscopic properties (density and lattice parameters) of pure TAGs as both crystals and melt with high accuracy, as well as reproduce the differences in enthalpies.

Influence of environmental conditions on accumulated polyhydroxybutyrate in municipal activated sludge

Poly(3-hydroxybutyrate) (PHB) was accumulated in full-scale municipal waste activated sludge at pilot scale. After accumulation, the fate of the PHB-rich biomass was evaluated over two weeks as a function of initial pH (5.5, 7.0 and 10), and incubation temperature (25, 37 and 55°C), with or without aeration. PHB became consumed under aerobic conditions as expected with first order rate constants in the range of 0.19 to 0.55 d−1. Under anaerobic conditions, up to 63 percent of the PHB became consumed within the first day (initial pH 7, 55°C). Subsequently, with continued anaerobic conditions, the polymer content remained stable in the biomass. Degradation rates were lower for acidic anaerobic incubation conditions at a lower temperature (25°C). Polymer thermal properties were measured in the dried PHB-rich biomass and for the polymer recovered by solvent extraction using dimethyl carbonate. PHB quality changes in dried biomass, indicated by differences in polymer melt enthalpy, correlated to differences in the extent of PHB extractability. Differences in the expressed PHB-in-biomass melt enthalpy that correlated to the polymer extractability suggested that yields of polymer recovery by extraction can be influenced by the state or quality of the polymer generated during downstream processing. Different post-accumulation process biomass management environments were found to influence the polymer quality and can also influence the extraction of non-polymer biomass. An acidic post-accumulation environment resulted in higher melt enthalpies in the biomass and, consequently, higher extraction efficiencies. Overall, acidic environmental conditions were found to be favourable for preserving both quantity and quality after PHB accumulation in activated sludge.

Evidence of Self-Association and Conformational Change in Nisin Antimicrobial Polypeptide Solutions: A Combined Raman and Ultrasonic Relaxation Spectroscopic and Theoretical Study

The polypeptide Nisin is characterized by antibacterial properties, making it a compound with many applications, mainly in the food industry. As a result, a deeper understanding of its behaviour, especially after its dissolution in water, is of the utmost importance. This could be possible through the study of aqueous solutions of Nisin by combining vibrational and acoustic spectroscopic techniques. The velocity and attenuation of ultrasonic waves propagating in aqueous solutions of the polypeptide Nisin were measured as a function of concentration and temperature. The computational investigation of the molecular docking between Nisin monomeric units revealed the formation of dimeric units. The main chemical changes occurring in Nisin structure in the aqueous environment were tracked using Raman spectroscopy, and special spectral markers were used to establish the underlying structural mechanism. Spectral changes evidenced the presence of the dimerization reaction between Nisin monomeric species. The UV/Vis absorption spectra were dominated by the presence of π → π* transitions in the peptide bonds attributed to secondary structural elements such as α-helix, β-sheets and random coils. The analysis of the acoustic spectra revealed that the processes primarily responsible for the observed chemical relaxations are probably the conformational change between possible conformers of Nisin and its self-aggregation mechanism, namely, the dimerization reaction. The activation enthalpy and the enthalpy difference between the two isomeric forms were estimated to be equal to ΔH1* = 0.354 ± 0.028 kcal/mol and ΔH10 = 3.008 ± 0.367 kcal/mol, respectively. The corresponding thermodynamic parameters of the self-aggregation mechanism were found to be ΔH2* = 0.261 ± 0.004 kcal/mol and ΔH20 = 3.340 ± 0.364 kcal/mol. The effect of frequency on the excess sound absorption of Nisin solutions enabled us to estimate the rate constants of the self-aggregation mechanism and evaluate the isentropic and isothermal volume changes associated with the relaxation processes occurring in this system. The results are discussed in relation to theoretical and experimental findings.

Study of influence of anomeric effect on conformational preferences using hybrid density functional theory (DFT) and natural bond orbital (NBO) interpretation

For the relationship between thermodynamic parameters, global hardness, global electronegativity, anomeric effect, structural parameters, and structural properties of dodecahedro-spiro [isochromene-3,2'-pyran] (A), dodecahedro-spiro [isothiocromene-3,2'- thiopyran) (B), dodecahedro-spiro [isochroman-3,2'-thiopyran] (C) and dodecahedro-spiro [isothiochrome-3,2'-pyran] (D) computational methods (B3LYP / 6-311 ++ G **) were used. Results show that the calculated Gibbs free energy and enthalpy differences between the axial- and equatorial- stereoisomers [i.e. ΔG = Geq – Gax, ΔH = Heq- Hax] decrease from compound A to compound B and from compound C to compound D. NBO results show that the anomeric effect associated with the electron delocalization is in benefit of the axial-stereoisomers and with the decrease of the anomeric effect, the values of global hardness (η), and global electronegativity (χ), from compound A to compound B and from compound C to Composition D is also decrease. The correlations between the global hardness, global electronegativity, anomeric effect, structural parameters, and thermodynamic parameters [ΔH, ΔG, and ΔS] of compounds A-D have been investigated. Also, it can be concluded that the stability energy obtained from the numerical values of the anomeric effect and the values calculated theoretically (B3LYP / 6-311 ++ G **) confirmed each other.

Key phonon modes to determine the phase transition of two dimensional Janus transition metal dichalcogenides: a DFT and tight-binding study.

Phase stability and the phase transition of Janus transition metal chalcogenides (TMDs) have become interesting issues that have not been fully resolved since their successful synthesis. By fitting the results from first principles calculations, a tight-binding dynamics matrix of the 1T' phase is constructed and the eigenvectors are also obtained. We propose a method to project the atomic motion causing the phase transition from 2H to 1T' onto these eigenvectors, and identify four key phonon modes which are the major factors to trigger phase transition. Temperature excitation is used to excite the key modes and the free energy criterion is used to determine the phase stability. The relatively large enthalpy difference between the 2H and 1T' phases favours the 2H one as the stable phase at low temperature. While the 1T' phase has a quick increase in vibrational free energy with rising temperature, especially for 1T' Janus TMDs which have a quicker increase in the total free energy than that of 1T' non-Janus TMDs, making them show a lower phase transition temperature. Our work will deepen our understanding of the phase transition behavior of 2D Janus TMDs, and the tight-binding dynamics matrix and the method to obtain the key modes will be a useful tool for further study of the phase transitions of 2D Janus TMDs and other related materials.

Heat management system of electric vehicle based on heat pump and energy recovery of removable battery

In order to manage the air-conditioning thermal system, battery thermal system and motor thermal system in a unified manner, the author proposes a self-developed integrated thermal management system for electric vehicles to recover battery energy. Firstly, the problems in the development of electric vehicles and the importance of thermal management system are introduced, secondly, the self-developed thermal management system scheme and the principle of each part are analyzed, the experimental results of thermal system in enthalpy difference chamber are also introduced. The experimental results show that: Under the double evaporation system, when the compressor speed is 4500 rpm, the maximum COP is 2.46, and the maximum COP charge is 1180 g, the maximum heat transfer capacity is 4819 W (wind side heat transfer + water side heat transfer), the evaporation temperature is 5.35?C, the evaporation superheat is 9.5?C, the condensation temperature is 59.3?C, the undercooling degree is 10.4?C, the suction pressure is 280 kPa, and the exhaust pressure is 1694 kPa. In conclusion, the thermal management system has great energy saving effect, which ensures that the electric vehicle range will not be greatly attenuated under winter heating conditions, and meets the requirements of comfort.

Numerical analysis of Darcy resistant Sutterby nanofluid flow with effect of radiation and chemical reaction over stretching cylinder: induced magnetic field

<abstract> <p>In this analysis, Sutterby nanofluid flow with an induced magnetic field at a nonlinear stretching cylinder is deliberated. The effects of variable thermal conductivity, Darcy resistance, and viscous dissipation are discussed. Thermal radiation and chemical reaction are considered to analyze the impact on the nonlinear stretching cylinder. The governing model of the flow problem is developed under the boundary layer approximation in terms of partial differential equations. Partial differential equations are transformed into ordinary differential equations by performing the suitable transformations. A numerical structure is applied to explain ordinary differential equations. The impact of each governing physical parameters on the temperature, concentration, skin friction, Sherwood, and Nusselt number is presented in graphs and tabular form. Increment in Prandtl number, which declined the curves of the temperature function. Temperature declined because the Prandtl number declined the thermal thickness as well as reduce the temperature of the fluid. Temperature curves showed improvement as Eckert number values increased because the Eckert number is a ratio of kinetic energy to the specific enthalpy difference between the wall and the fluid. As a result, increasing the Eckert number causes the transformation of kinetic energy into internal energy via work done against viscous fluid stresses.</p> </abstract>

Alkali Cation Engineered Chemical Self-Oxidation of Copper Oxide Nanowire-Based Photocathodes.

Hydrogen energy production through photoelectrochemical (PEC) water splitting has great potential in the field of renewable energy. This study focuses on the hydration enthalpy difference of cations (Li+ , Na+ , and K+ ) in an aqueous solution for the chemical self-oxidation process without an external applied bias. The thickness of the cation/H2 O double layer is controlled. The starting materials are low-cost copper foil and the synthesis uses alkali cation-engineered chemical self-oxidation. Li+ ions are strongly attracted to water molecules. This forms a sufficient OH- layer on the Cu foil surface. By accelerating the oxidation reaction, a large surface area of Cu(OH)x nanowires (NWs) with high purity and a uniform shape are obtained. This optimal p-type Cu2 O NWs photocathode is CuO-free, has the highest conductivity, and is fabricated through phase transition using precise vacuum annealing. The other alkali cations produce the Cu2 O/CuO mixed or CuO phases that degrade the PEC performances with severe corrosive reactions. The Cu/Li : Cu2 O/AZO/TiO2 /Pt photocathode has a 50 h stability with a photocurrent density of 8.4 mA cm-2 at 0 VRHE . The fabricated photoelectrode did not structurally collapse after stability measurements during this period. The captured hydrogen production was in agreement with the calculated faradaic efficiency.

Experimental investigation on the heating performance of a R410A vapor-injection heat pump of an electric bus in cold regions

To study the heating performance of a R410A SCVI (sub-cooler vapor-injection) heat pump of an electric bus and solve its practical application problems in cold regions, the experimental setups were established. The experimental tests were carried out in the enthalpy difference chamber. The influence of ambient temperature, compressor speed, vapor-injection mass flow ratio and indoor air temperature on the system were considered. The minimum ambient temperature for the experiment is −25 °C. The results show that when the compressor speed increases from 3000 rpm to 5400 rpm, the heating capacity increases by 43.7 % but the COP (coefficient of performance) decreases by 11.1 %. As the ambient temperature decreases, the heating capacity of N-VIHP (non-vapor-injection heat pump) decreases more. The heating capacity of the VIHP (vapor-injection heat pump) system has a maximum increase of 3.84 kW, with an overall increase of 4.9 % ∼ 33.2 %, and the increase of COP is 2.7 % ∼ 15.2 % compared with N-VIHP. The optimal vapor-injection mass flow ratio is 0.32 ∼ 0.44 for this electric bus R410A SCVI heat pump. The vapor-injection circuit electronic expansion valve does not need to be opened all the time. It is better to open it when the ambient temperature is below −5 °C. The VIHP has better heating performance at low temperature and is more suitable for electric buses in cold regions.

Fabrication process development and basic evaluation of eggshell-based column packing material for reversed-phase preparative separation

Purification of basic drugs in reversed-phase mode is often difficult, mainly due to adsorption of positively charged compounds to the silica gel-based stationary phase. Since this adsorption can be suppressed under alkaline condition, columns with alkali-resistance are required. In addition, compounds with acid-sensitive structures are sometimes degraded during separation on silica gel-based columns which exhibit acidity due to their surface structure. We prepared an alkali-resistant reversed-phase packing material, Eggshell-PMAcO based on eggshells modified with an amphiphilic copolymer, poly(maleic acid-alt-1-octadecene) (PMAcO). The height equivalent to a theoretical plate (HETP) of the Eggshell-PMAcO column was improved by surface treatment with ammonium acetate buffer (900 mM, pH = 3.7), which is an inexpensive reagent, and the retention behavior for hydrophobic compounds was compared to a typical ODS column based on silica gel, resulting in sufficient selectivity of the eggshell-based column for hydrophobic compounds, as indicated by the ratio of retention factors of pentylbenzene and butylbenzene (Eggshell-PMAcO column: 1.55, ODS column: 1.65). Column temperature-dependent retention behavior of naphthalene was investigated in the temperature range from 25 °C to 45 °C, followed by the calculation of thermodynamic parameters. There was little difference in the standard molar enthalpy (Eggshell-PMAcO: −19.6 kJ/mol, ODS: −21.7 kJ/mol). The absolute value of the standard free Gibbs energy for the Eggshell-PMAcO column was much smaller than that of the ODS column (Eggshell-PMAcO: −0.284 kJ/mol, ODS: −13.0 kJ/mol), indicating that the Eggshell-PMAcO column had a weaker retention strength for naphthalene than the ODS column mainly due to the large difference in the standard molar entropy (Eggshell-PMAcO: −64.9 J/mol K, ODS column: −29.2 J/mol K). The retention capacities for imipramine under neutral (water/methanol) and alkaline (0.1% triethylamine water/methanol) conditions were 0.2 mg and 5 mg, respectively, based on injection mass-dependent HETP, retention factor and symmetry factor. Finally, the prepared column was applied to the purification of a building block for nucleic acid drugs. This study demonstrated that reversed-phase columns, which can be fabricated from eggshells and an amphiphilic copolymer in an inexpensive and eco-friendly way, have the ability to purify basic compounds and acid-sensitive compounds.

Thermodynamic analysis of metal oxides, metal peroxides and metal hydrides

The standard entropy differences between metal oxides (metal peroxides) and metal elements Δ S were roughly expressed by the following equation, |Δ S | ∝ Rln|Δ V |, R: gas constant, Δ V : volume differences below 10 cm 3 /molO 2 , which is similar to the relation of metal hydrides. It was presumed that the entropy of oxygen in the metal oxides and the metal peroxides, together with the entropy of hydrogen in the metal hydrides can be controlled by the thermodynamics of ideal gas. Those volume differences were increased by increasing of the work function based on the small ion binding properties. However, the absolute values of the standard enthalpy differences |Δ H | had large values at Δ V of -22 to 8 cm 3 /molO 2 . The thermodynamic stabilities which are the absolute values of the standard enthalpy differences decreased in the order, metal oxides > metal peroxides > metal hydrides. • The relation between standard entropy and volume differences Δ S, Δ V was analyzed. • |Δ S | linearly increased with ln|Δ V | below 2⊡3⊡ • The slope was approximately gas constant R. • |Δ H | had large values at Δ V of -22 to 8cm 3 /molO 2 ,Δ H standard enthalpy differences. • |Δ H | decreased in the order, metal oxides > metal peroxides > metal hydrides.

Thermodynamics of trans/gauche conformational equilibria and vibrational spectra of 1,2-dihaloethanes in various media.

The recently developed efficient protocols to implicit [Grimme et al., J. Phys. Chem. A 125, 4039-4054 (2021)] and explicit quantum mechanical modeling of non-rigid molecules in solution [Katsyuba et al., J. Phys. Chem. B 124, 6664-6670 (2020)] are used to describe conformational equilibria of 1,2-dichloroethane and 1,2-dibromoethane in various media. Two approaches for evaluation of trans/gauche free energy differences, ΔGt-g, are compared: (a) direct ΔGt-g computation in implicit solution; (b) the use, together with experimental intensities, of infrared absorption coefficients and Raman scattering cross sections computed for each explicitly modeled solution. The same cluster model of a solute surrounded by the first solvation shell of solvent molecules was used to simulate both Raman and IR spectra. The good agreement between the two approaches indicates the reliability of both methods. The importance of using correct absorption coefficients and Raman scattering factors for each medium is discussed. The ΔGt-g estimates from both implicit and explicit solvation simulations were combined with experimentally measured enthalpy differences ΔHt-g available in the literature to obtain condensed-state ΔSt-g estimates.