Enthalpies Of Formation Research Articles

Formation and Migration Enthalpy from Elemental and Cooperative Diffusion in Lead Silicate Supercooled Liquid and Glass

Formation and Migration Enthalpy from Elemental and Cooperative Diffusion in Lead Silicate Supercooled Liquid and Glass

Deep insights into the optoelectronic properties of AgCdF3-based perovskite solar cell using the combination of DFT and SCAPS-1D simulation

The main focus of this research is to explore the properties and photovoltaic application of AgCdF3, and hence, initially, the CASTEP software was used in this study to assess the structural, optical, mechanical, and electrical characteristics of the AgCdF3 perovskite absorber layer within the context of the density functional theory (DFT) method. AgCdF3 resulting from the structural research is confirmed to be chemically and thermodynamically stable by the estimated tolerance factor and formation enthalpy. According to the band structure analysis, AgCdF3 is an indirect band gap semiconductor with a band gap of 1.106 eV, where the electrons of Cd-4d and F-2s dominate the band edges of this semiconductor. Analysis of mechanical properties revealed that the AgCdF3 cubic perovskite has a stable structure and enhanced ductility, indicating superior machinability. After completing the DFT analysis, a one-dimensional solar cell capacitance simulator 1D (SCAPS-1D) was used with three popular electron transport layers (ETLs), including ZnO, PCBM, and C60, to examine the photovoltaic (PV) performance of various AgCdF3-based solar cell heterostructures. Based on simulation findings, the device design with ITO/ZnO/AgCdF3/CuI/Au showed the highest photoconversion efficiency compared to the other configurations. A detailed analysis was conducted for the aforementioned configurations to determine the impact of variations in the absorber and ETL thickness on PV performance. Moreover, the effects of the three designs were assessed in terms of function, generation and recombination rate, capacitance, operating temperature, series and shunt resistance, and Mott-Schottky. Thus, this comprehensive simulation with validation results demonstrated the true potential of AgCdF3 absorber with appropriate ETLs such as ZnO, PCBM, and C60; on the other hand, the CuI as hole transport layer (HTL), paving the way for promising studies to develop high-efficiency AgCdF3 PSCs for the photovoltaic industry.

Anion replacement effect on the structural, magnetoelectronic, and optical features of all inorganic halide double perovskites K2LiMoX6 (X= Br, I) for spintronic and optical devices

Herein, the geometrical, magnetic, optoelectronic, thermoelectric features of K2LiMoX6 (X = Br, I) have been simulated by DFT. The FP-LAPW approach is employed via Wien2k software. To confirm the thermodynamic and structural stability of the K2LiMoX6 (X = Br, I) compounds, the tolerance factor (τ) and formation enthalpy are calculated. The predicted spin-polarized band structure (BS) and density of states (DOS) display p-type semiconductor character via direct band gap at X-X symmetry points in both spin versions. The ferromagnetic (FM) character was confirmed from magnetic moments (MTot) which are 3.00090, and 3.00014 μB for K2LiMoBr6, and K2LiMoI6, correspondingly. The materials light absorbance was observed in the range of visible to ultraviolet (UV) zone, thereby enhancing their significance for photocell and optoelectronic devices. In addition, both halides exhibit optimal figure of merit (ZT) which make these materials as promising candidates for efficient heat energy conversion technologies. The outcomes of the studied compounds provide a new path for researchers for the applications of spintronic and optical gadgets.

Revisiting the thermodynamic properties of the ZrCr2 Laves phases by combined approach using experimental and simulation methods

A comprehensive study of ZrCr2 Laves phases is important for both fundamental research and technological applications. The ZrCr2 compound is a typical precipitate observed in Zr-based alloys including the newly developed Cr-coated Zr cladding known as Accident Tolerant Fuel cladding. The brittle behavior of the Laves phases and the low melting point at the interface zone between the precipitates and the Zr matrix are considered as governing the thermomechanical behaviors of these newly developed nuclear fuel claddings for normal operating conditions but more dramatically in case of Loss Of Coolant Accident (LOCA) conditions. The aim of the present study is to investigate the various ZrCr2 Laves polymorphs and their thermodynamic features particularly where conflicts exist in the literature. Based on diffraction experiments of annealed samples, it has been established that the transformation from the C14 high-temperature form to the C15 low-temperature form is of displacive nature without the C36 polymorph forming as an intermediate phase. The stable and metastable domains of C14 and C15 and their thermodynamic properties have been determined. The specific heat of both C14 and C15 types was measured over a wide range of temperatures from 2 to 1063 K by coupling relaxation calorimetry and DSC. The experimental data were fitted using a modified Einstein model. The room temperature entropies of the C14 and C15 phases were evaluated. The enthalpy of formation was measured for the first time using drop solution calorimetry in liquid Al at 1173 K in a Tian–Calvet calorimeter. The experimental value is in good agreement with Density Functional Theory (DFT) calculations. Finally, all these new results are discussed regarding the abundant literature on the ZrCr2 Laves phases.

Quasi-Van der Waals Epitaxial Growth of γ'-GaSe Nanometer-Thick Films on GaAs(111)B Substrates.

GaSe is an important member of the post-transition-metal chalcogenide family and is an emerging two-dimensional (2D) semiconductor material. Because it is a van der Waals material, it can be fabricated into atomic-scale ultrathin films, making it suitable for the preparation of compact, heterostructure devices. In addition, GaSe possesses unusual optical and electronic properties, such as a shift from an indirect-bandgap single-layer film to a direct-bandgap bulk material, rare intrinsic p-type conduction, and nonlinear optical behaviors. These properties make GaSe an appealing candidate for the fabrication of field-effect transistors, photodetectors, and photovoltaics. However, the wafer-scale production of pure GaSe single-crystal thin films remains challenging. This study develops an approach for the direct growth of nanometer-thick GaSe films on GaAs substrates by using molecular beam epitaxy. It yields smooth thin GaSe films with a rare γ'-polymorph. We analyze the formation mechanism of γ'-GaSe using density-functional theory and speculate that it is stabilized by Ga vacancies since the formation enthalpy of γ'-GaSe tends to become lower than that of other polymorphs when the Ga vacancy concentration increases. Finally, we investigate the growth conditions of GaSe, providing valuable insights for exploring 2D/three-dimensional (3D) quasi-van der Waals epitaxial growth.

First principles computation of novel hydrogen-doped CsSrO3 with excellent optoelectronic properties as a potential photocatalyst for water splitting

This research exhaustively inquired about the structural, photocatalytic, mechanical, and optoelectronic characteristics of the cubic perovskite CsSrO3−x Hx with the CASTEP code’s implementation of the GGA-PBE formalism. It aims to examine the characteristics of CsSrO3−xHx cubic perovskite with varied concentrations of substituents (x = 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, and 3.0). The stability and synthesizability of the compound are guaranteed by the values of elastic constants and negative formation enthalpies. As H-insertion increases, there are variations in the values of anisotropy and elastic moduli. A semiconductor’s wide bandgap narrows as dopant concentration rises, changing its nature from indirect to direct. The findings imply that the compound’s electronic characteristics can be altered through the application of dopants, rendering them appropriate for a range of optoelectronic uses. The inclusion of hydrogen caused the structural change from cubic to tetragonal and orthorhombic. The distortion caused the lattice parameters to vary in values. Tolerance factor lies in range of 0.7–1 that ensures structural stability of CsSrO3−x Hx. Our computed results reveal the anisotropic nature of our compound. The obtained bandgap for CsSrO3−xHx indicates that both O2 evolution and H2 reduction are allowed since the requisite redox potentials are satisfied. Photocatalytic properties of CsSrO2.4H0.6 reveals that it is the best doped system as a potential candidate for water-splitting photocatalysis, as it has equal effectiveness to both oxidation and reduction processes. The bandgap was shown to decrease from 5.33 eV to 2.812 eV at complete hydrogen insertion, which also had an impact on the material’s optoelectronic characteristics. All the optical considerations such as dielectric functions, refractive indices, extinction coefficients, optical reflectivity, absorption coefficients, and loss functions are also thoroughly explained. The material exhibits mechanical stability along with ionic and covalent bonding.

Thermochemical Research on Furfurylamine and 5-Methylfurfurylamine: Experimental and Computational Insights.

The need to transition from fossil fuels to renewables arises from factors such as depletion, price fluctuations, and environmental considerations. Lignocellulosic biomass, being abundant, and quickly renewable, and not interfering with food supplies, offers a standout alternative for chemical production. This paper explores the energetic characteristics of two derivatives of furfural-a versatile chemical obtained from biomass with great potential for commercial sustainable chemical and fuel production. The standard (p° = 0.1 MPa) molar enthalpies of formation of the liquids furfurylamine and 5-methylfurfurylamine were derived from the standard molar energies of combustion, determined in oxygen and at T = 298.15 K, by static bomb combustion calorimetry. Their standard molar enthalpies of vaporization were also determined at the same temperature using high-temperature Calvet microcalorimetry. By combining these data, the gas-phase enthalpies of formation at T = 298.15 K were calculated as -(43.5 ± 1.4) kJ·mol-1 for furfurylamine, and -(81.2 ± 1.7) kJ·mol-1 for 5-methylfurfurylamine. Furthermore, a theoretical analysis using G3 level calculations was performed, comparing the calculated enthalpies of formation with the experimental values to validate both results. This method has been successfully applied to similar molecules. The discussion looks into substituent effects in terms of stability and compares them with similar compounds.

Understanding the mechanical, opto-electronic, and thermoelectric properties of lead-free Silver based perovskites Cs2YAgX6 (X=Cl, Br, I): A computational study

The magnificent and diversified optoelectronic, thermoelectric, and mechanical capabilities of double perovskites (DPs) have made them an emergent material in optoelectronics. This study performs a DFT technique for examining the structural, optoelectronic, and thermoelectric properties of halide-based double perovskite Cs2YAgX6(X = Cl, Br, I) compounds. When halogens are switched from Cl to I, the lattice parameter of these compounds which are members of the cubic family increases. The enthalpy of formation, tolerance factor, and Pugh's ratio are utilized to validate structural stability. Pugh's ratio explains the ductile nature of the compounds under scrutiny Due to their wide bandgap (4.90 eV, 4.70eV, and 4.11eV), Cs2YAgX6(X = Cl, Br, I) double perovskites are intriguing options for optoelectronic devices, owing to a detailed analysis of their optoelectronic properties. The assessed power factor and thermal conductivity yield in high merit values (0.94–0.96) reveal the material's potential for thermoelectric devices. These examinations establish a comprehensive awareness of these materials for future use.

First-principles investigation on the effect of Nb and Ta doping on the hydrogen storage performance of ZrCo

The ZrCo alloy has demonstrated significant potential in the storage of hydrogen and its isotopes, but there are still some issues such as insufficient dynamic properties. In this paper, the impact of Nb/Ta doping on the hydride stability of ZrCo was examined based on the density functional theory, and the improvement of H diffusion through Nb/Ta doping was investigated. The focal point lies in exploring the influence of Nb/Ta doping on the alloy’s resistance to poisoning and disproportionation. The results demonstrate that the crystal lattice maintains mechanical and thermodynamic stability even after Nb/Ta doping. Nb/Ta doping induces lattice contraction in ZrCo-Hx (x = 1.0–3.0) and reduce the enthalpy of formation, thereby facilitating cyclic hydrogen storage. Additionally, Nb/Ta doping enhances the diffusion performance of H atoms within O-containing lattice, improving the alloy’s resistance to poisoning. Furthermore, Nb/Ta doping lowers the energy barrier of H atoms escape from 8e sites, promoting anti-disproportionation.

Theoretical exploration of novel compounds in Sr(B,C)x (x = 7,8) at high pressure

Boron-carbon-based compounds have attracted considerable attention due to their exceptional properties and increasing applications in industry. In this study, we conducted a systematic structural prediction of the SrBxC7-x and SrBxC8-x systems under ambient and high pressures up to 20 GPa using an unbiased global structure search. Through the calculations of formation enthalpy and phonon dispersion curves, we identified three new compounds, namely SrB5C2, SrB6C and SrB5C3, as thermodynamically and dynamically stable under ambient pressure and high pressures up to 20 GPa. Calculations of mechanical properties reveal that these three compounds have significant mechanical strength, with estimated theoretical Vickers hardness values ranging from 23.2 to 39.8 GPa. Electronic structure calculations suggest that both SrB5C2 and SrB5C3 are hole conductors, with the bands crossing the Fermi level, and SrB6C is a semiconductor with an indirect bandgap of 2.4 eV. The electron-phonon coupling calculations using the Migdal-Eliashberg theory indicate that SrB5C2 exhibits superconductivity at 10.5 K under ambient pressure, while SrB5C3 shows superconductivity at a much lower temperature of 0.4 K. This finding adds to our knowledge of boron-carbide materials and provides valuable insights for the development of similar materials with good mechanical properties.

General Method for Predicting Interface Bonding at Various Oxide–Metal Interfaces

Interface termination bonding between metal oxide and metals is discussed from the viewpoint of thermodynamics. The method of interface termination prediction proposed by the authors for Al2O3–metal and ZnO–metal interfaces is extended to a general interface between metal-oxide and metals. The extension of the prediction method to the interface between metal oxides and elemental semiconductors is also discussed. Information on interface bonding was extracted by carefully examining the experimental results and first-principles calculations in the references. The extracted information on interface bonding from references is compared with the results obtained via the proposed prediction method. It is demonstrated that interface termination bonding can be predicted by extending the method to oxide–metal interfaces in general, when there is no interface reaction such as the reduction of oxide, oxidation of metal, or mixed oxide formation. The method uses only basic quantities of pure elements and the formation enthalpy of oxides. Therefore, it can be applied to most of the metals (including elemental semiconductors) in the periodic table and metal oxides with one stable valence. The method is implemented as a software, “InterChemBond”, and can be used free of charge.

Probing the opto-electronic, phonon spectrum, and thermoelectric properties of lead-free fluoride perovskites A2GeSnF6 (A = K, Rb, Cs) for energy harvesting devices

The present work employs density functional theory to explore the structural, optoelectronic, and thermoelectric attributes of the halide-based double perovskite A2GeSnF6 (A = K, Rb, and Cs) compounds. The stable phonon dispersion spectrum affirms dynamical stability, whereas the enthalpy of formation and tolerance factor evaluated collectively verify structural stability. Considering the Tran Blaha modified Becke Johnson potentials (mBJ), the predicted direct band gaps along the symmetry point are 3.19 eV for K2GeSnF6, 3.16 eV for Rb2GeSnF6 and 3.12 eV Cs2GeSnF6. According to an in-depth examination of the optoelectronic features, A2GeSnF6 (A = K, Rb, and Cs), double perovskites are assuring contenders for optoelectronic devices due to their suitable bandgap. The extremely high figure of merit values (0.94–0.97) obtained from the numerical calculation of power factor and thermal conductivity suggest the intriguing prospects of these compositions for thermoelectric devices. These studies offer a perceptive comprehension of the materials for their potential applications in the future.

Thermodynamic properties of 3-(1,5-diphenylpyrrol-2-yl)- propanoic acid

Using precision equipment, the enthalpies of vaporization, fusion and formation in the condensed state of 3-(1,5-diphenylpyrrol-2-yl)-propanoic acid were experimentally determined. The enthalpy of sublimation at 298 K and the enthalpy of formation in the gaseous state were calculated. A comparative analysis of the experimentally determined values with theoretically calculated values using additive calculation methods is given.

Pressure-driven semiconducting to metallic transition in francium tin trihalides perovskite with improved optoelectronic performance: A DFT study

The objective of our study was to analyze the mechanical, magnetic, elastic, electrical, and optical characteristics of the halide-based perovskite FrSnX3 (X = Cl, Br, and I) at hydrostatic pressures ranging from 0 to 6 GPa. We conducted this analysis using first-principles calculations based on density functional theory. The thermodynamic and mechanical stability of the complex FrSnX3 (X = Cl, Br, and I) were calculated based on its formation enthalpy and elastic constant characteristics. The compound was found to be ductile and stable. FrSnCl3, FrSnBr3, and FrSnI3 are all classified as semiconductors according to band calculations. Their respective bandgaps are 1.046, 0.675, and 0.485 eV, respectively. These values remain constant when hydrostatic pressure is not applied. The bandgap and density of states of the three halides were examined to observe their variations with increasing induced pressure. The bandgaps of FrSnCl3, FrSnBr3, and FrSnI3 were measured to be 0 eV at pressures of 6, 4, and 2 GPa, respectively. In addition, a comprehensive study was conducted on the optical properties of cubic perovskites FrSnX3 (X = Cl, Br, and I) under different hydrostatic pressures ranging from 0 to 6 GPa. The investigation focused on analyzing the optical absorption, reflectivity, and refractive index, as well as the imaginary and real components of the dielectric functions. Under high pressure, the compound exhibited higher absorption capabilities for all compounds within the 10–13 eV range, transforming into a conductor. This property makes it well-suited for utilization in the UV spectrum. Chlorine exhibits the greatest absorption among all chemicals, whereas iodine demonstrates the least absorption. The reflectance values of all compounds range from 12% to 16% and increase with increasing pressure. At the energy level of zero, the refractive index’s real component ranges from 1.25 to 1.7, and it increases with increasing pressure. Chlorine has a relatively low refractive index compared to iodine. Bromine has the most pronounced variance. The dielectric characteristics typically vary from 4.5 to 7.5 F/m. As pressure increases, the charge storage capacities of all compounds increase. However, among these compounds, iodine has the highest capacity, while chlorine (Cl) has the lowest. The hydrostatic pressure applied to the structure FrSnX3 (X = Cl, Br, and I) causes it to become harder and more ductile. This is evident from the increasing values of the bulk, Young’s, and shear modulus, as well as the elastic constants (C11 and C12). We optimized the band structure and density of states by aligning the electrons in a co-linear location and assessed the magnetic properties. The diamagnetic characteristic of the FrSnX3 compound (where X = Cl, Br, and I) remained unchanged when subjected to increasing pressure. The results indicate that the perovskite material has exceptional absorption properties, indicating a change in its behavior from a transistor to a metal. The numerical findings highlight the potential applications of this material in photovoltaic cells, ultraviolet light absorbers, and optoelectronic devices.

A high density and low sensitivity carrier explosive promising to replace TNT: 3-Bromo-5-fluoro-2,4,6-trinitroanisole

To address the issues of high saturated vapor pressure, high toxicity, and high viscosity of TNT, this article used a chemical method to synthesize a new carrier explosive BFTNAN. The prepared samples were characterized using scanning electron microscope(SEM), energy spectrum(EDS), x-ray diffraction(XRD), infrared spectrum(IR), x-ray photoelectron spectroscopy(XPS), nuclear magnetic resonance, and elemental analysis techniques. The enthalpy of formation of BFTNAN was measured using a specialized calorimeter that is specially used in testing of explosives and powders. The thermal decomposition performance of BFTNAN was tested by DSC technology. Meanwhile, the mechanical sensitivity, thermal sensitivity, and detonation performance of BFTNAN based melt-cast explosive was also tested. The results of characterizations showed that the prepared sample was indeed BFTNAN. The enthalpy of formation of BFTNAN was determined as ΔHf,BFTNAN = −72.6 kJ·mol−1. At a heating rate of 20 °C·min−1, the thermal decomposition peak of BFTNAN is at TP = 250.6 °C, and the activation energy is EK = 80 kJ·mol−1, which is closed to the Tp and EK values of TNT. This indicates that BFTNAN is a relatively easy to decompose explosive, but the decomposition rate is not fast. The critical temperature for thermal explosion of BFTNAN reached Tb = 216 °C, which is also closed to the Tb value of TNT. The impact and friction sensitivity of BFTNAN were lower than those of TNT, which was closed to those of DNAN. The thermal sensitivity of BFTNAN is lower than TNT. The detonation velocity and heat of explosion of BFTNAN based melt-cast explosive were distinctly higher than those of TNT based explosive. Especially, BFTNAN based melt-cast explosive were of the advantages in chemical energy storage, work capacity, brisance, and ability of acceleration metals.

Batch synthesis of 2,4,6‐trinitro‐3‐bromoanisole and its thermolysis and combustion performance

AbstractA new carrier explosive TNBA was batch synthesized by a chemical method. The prepared samples were characterized using SEM, EDS, XRD, IR, XPS, nuclear magnetic resonance, and elemental analysis techniques. The enthalpy of formation of TNBA was measured using a specialized calorimeter that is specially used in testing of explosives and powders. The thermal decomposition performance of TNBA was tested by DSC technology. Meanwhile, the combustion performance of TNBA was also tested. The results of characterizations showed that the prepared sample was indeed TNBA. The enthalpy of formation of TNBA was determined as ΔHf,TNBA=+48.5 kJ/mol. At a heating rate of 20 °C/min, the thermal decomposition peak of TNBA is at TP=285.3 °C, and the activation energy is EK=91 kJ/mol, which is higher than the Tp and EK values of TNT. This indicates that TNBA is a relatively easy to decompose explosive, but the decomposition rate is not fast. The critical temperature for thermal explosion of TNBA reached Tb=247 °C, which is higher than the Tb value of TNT, slightly lower than the Tb value of DNAN, and significantly higher than the Tb value of DNTF, TNAZ, and MTNP. The combustion performance test results showed that the TNBA sample has the highest combustion pressure and the highest pressurization rate; and the TNBA sample has the highest combustion temperature; however, due to the high oxygen balance, the combustion heat of TNBA samples in excess pure oxygen is not the highest.

Machine learning to explore high-entropy alloys with desired enthalpy for room-temperature hydrogen storage: Prediction of density functional theory and experimental data

Safe and high-density storage of hydrogen, for a clean-fuel economy, can be realized by hydride-forming materials, but these materials should be able to store hydrogen at room temperature. Some high-entropy alloys (HEAs) have recently been shown to reversibly store hydrogen at room temperature, but the design of HEAs with appropriate thermodynamics is still challenging. To explore HEAs with appropriate hydride formation enthalpy, this study employs machine learning (ML), in particular, Gaussian process regression (GPR) using four different kernels by training with 420 datum points collected from literature and curated here. The developed ML models are used to predict the formation enthalpy of hydrides for the TixZr2-xCrMnFeNi (x = 0.5, 1.0 and 1.5) system, which is not in the training set. The predicted values by ML are consistent with data from experiments and density functional theory (DFT). The present study thus introduces ML as a rapid and reliable approach for the design of HEAs with hydride formation enthalpies of −25 to −39 kJ/mol for hydrogen storage at room temperature.

Compound database for gaseous metal hydroxides and oxyhydroxides

In this study computational methods are used to derive thermochemical data for Sc, Fe, Co, Ni, and Hf hydroxides and oxyhydroxides. As done previously, molecular geometries and vibrational modes were derived with DFT methods; for the enthalpies of formation more computationally intensive coupled cluster methods were necessary. For each species ΔfHo(298), So(298), and Cp in the form A + BT + CT2 + D/T + E/T2 with A, B, C, D, and E fitted constants are presented. These are combined with previously reported calculations for Al, Cr, Si, Ta, Al, Zr, Y, Yb, Gd, and Mn to build a compound database for metal hydroxides and oxyhydroxides. Sample calculations for applications where high temperature water vapor is encountered are shown. The majority of the database was generated from ab initio calculations; however, experiments were critical benchmarks for many of the species.

Structural and Electronic Factors behind the Electrochemical Stability of 3D-Metal Tungstates under Oxygen Evolution Reaction Conditions.

Transition metal tungstates (TMTs) possess a wolframite-like lattice structure and preferably form via an electrostatic interaction between a divalent transition metal cation (MII) and an oxyanion of tungsten ([WO4]2-). A unit cell of a TMT is primarily composed of two repeating units, [MO6]oh and [WO6]oh, which are held together via several M-μ2-O-W bridging links. The bond character (ionic or covalent) of this bridging unit determines the stability of the lattice and influences the electronic structure of the bulk TMT materials. Recently, TMTs have been successfully employed as an electrode material for various applications, including electrochemical water splitting. Despite the wide electrocatalytic applications of TMTs, the study of the structure-activity correlation and electronic factors responsible for in situ structural evolution to electroactive species during electrochemical reactions is still in its infancy. Herein, a series of TMTs, MIIWVIO4 (M = Mn/Fe/Co/Ni), have been prepared and employed as electrocatalysts to study the oxygen evolution reaction (OER) under alkaline conditions and to scrutinize the role of transition metals in controlling the energetics of the formation of electroactive species. Since the [WO6]oh unit is common in the TMTs considered, the variation of the central atom of the corresponding [MO6]oh unit plays an intriguing role in controlling the electronic structure and stability of the lattice under anodic potential. Under the OER conditions, a potential-dependent structural transformation of MWO4 is noticed, where MnWO4 appears to be the most labile, whereas NiWO4 is stable up to a high anodic potential of ∼1.68 V (vs RHE). Potential-dependent hydrolytic [WO4]2- dissolution to form MOx active species, traced by in situ Raman and various spectro-/microscopic analyses, can directly be related to the electronic factors of the lattice, viz., crystal field splitting energy (CFSE) of MII in [MO6]oh, formation enthalpy (ΔHf), decomposition enthalpy (ΔHd), and Madelung factor associated with the MWO4 ionic lattice. Additionally, the magnitude of the Löwdin and Bader charges on M of the M-μ2-O-W bond is directly related to the degree of ionicity or covalency in the MWO4 lattice, which indirectly influences the electronic structure and activity. The experimental results substantiated by the computational study explain the electrochemical activity of the TMTs with the help of various structural and electronic factors and bonding interactions in the lattice, which has never been realized. Therefore, the study presented here can be taken as a general guideline to correlate the reactivity to the structure of the inorganic materials.

Thermodynamics assessment of the Erbium-Ruthenium system by combining the Ab-initio and CALPHAD methods

ABSTRACT In the present study, the erbium-ruthenium system was optimised using the CALPHAD approach. The thermodynamic properties and the phase diagram were evaluated. The enthalpies of formation of the intermetallic compounds for the binary system Er-Ru were calculated by ab- initio methods. The liquid phase was treated with the exponential model, while a solution model was applied to represent the HCP (Er, Ru) solid solution. The five intermetallic compounds Er3Ru, Er5Ru2, Er3Ru2, ErRu2, and Er44Ru25 were considered as stoichiometric compounds. The calculations are in good agreement with the phase diagram information and experimental thermodynamic values documented in the literature.