Phase Thermodynamic Properties Research Articles

Experimental investigation and thermodynamic assessment of the Al–Er system

The phase equilibria of the Al–Er binary system have been investigated through both experiments and CALPHAD assessment. The phase relationship in the compositional range of 0–50 at. % Er was experimentally redetermined using scanning electron microscopy (SEM) with Energy Dispersive Spectroscopy (EDS), electron probe micro analysis (EPMA) with wavelength dispersive spectrometer (WDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results confirmed the existence of the Al3Er phase (Al3Ho-type structure) with limited homogeneity range in the Al–Er system. It was formed through the peritectic reaction L + Al2Er ↔ Al3Er at 1105.3 ± 2.4 °C. While the Al17Er2 phase was proved to be metastable in the present work. A full thermodynamic optimization of the Al–Er binary system has been carried out by utilizing the current experimental data as well as all available results in the previous publications. A set of self-consistent thermodynamic parameters for the Al–Er system was established. The calculated phase diagram and thermodynamic properties agree well with the available data. The artificial inverted liquid-liquid miscibility gap at high temperature in the previous evaluation is removed.

Pressure prediction of phase stability, anisotropic elasticity, and thermodynamic properties of Ti2AC (A = Cd, In) ternary compound

AbstractIn this study, the effects of high pressure on phase stability, anisotropic elasticity, and thermodynamic properties of Ti2AC (A = Cd, In) were predicted by using first‐principles based on density functional theory. The negative formation enthalpy indicates that Ti2AC (A = Cd, In) is thermodynamically stable at pressures of 0–50 GPa. The elastic constants and polycrystalline moduli of Ti2AC (A = Cd, In) increase with increasing pressure, while its elastic anisotropies decrease with increasing pressure. The density of states demonstrates that no phase transition occurs in the pressure range 0–50 GPa. In addition, the influences of high pressure (up to 50 GPa) and temperature (up to 2000 K) on the thermodynamic properties of Ti2AC (A = Cd, In) were systematically studied based on the quasi‐harmonic Debye model. Finally, the sound velocities and minimum thermal conductivities are also discussed.

Thermodynamic modeling of the Mg–Mn–Zn system based on the refinement of the Mg–Zn and Mn–Zn systems

Based on the critical evaluation of the experimental data in the literature, the Mg–Mn–Zn system was assessed utilizing the CALPHAD (CALculation of PHAse Diagram) method. The binary Mg–Zn and Mn–Zn systems were re-assessed to obtain a better thermodynamic description. The solution phases, including liquid, (Mg), (δMn), (γMn), (βMn), (αMn), and (Zn), were described using the substitutional solution model. The solid Zn was treated as Hcp_A3 not Hcp_Zn in the present work. The compounds with and without solubility range were described by the sub-lattice model and stoichiometric phases. The presently calculated phase diagram and thermodynamic properties of the Mg–Zn system demonstrated obvious improvements in comparison with the previous work. Thermodynamic parameters for the Mg–Mn–Zn system were obtained by extrapolating the binaries and adjusting the ternary parameters based on reliable experimental data in the literature. Comparing the calculated results with the experimental data, a good agreement was achieved, which confirms the reliability of the presently obtained thermodynamic parameters.

Assessment of the Mg–Al–Sb system supported by experiments and extrapolation to the Mg–Al–Sn–Sb quaternary system

The phase equilibria and transformation temperatures of the Mg–Al–Sb ternary system were investigated via thermodynamic modeling coupled with key experiments. The isothermal section of the Mg-rich corner at 400 °C and two vertical sections in the Mg–Al–Sb ternary system were constructed by the metallographic analysis and thermal analysis. No ternary compound was found in the Mg-rich corner. The thermodynamic modeling of Al–Sb and Mg–Al–Sb systems was carried out using the CALculation of PHAse Diagram (CALPHAD) approach. The associated solution model was used to describe the short-range ordering for the liquid phase. The calculated phase diagram and thermodynamic property of the Al–Sb system are consistent with most of the experimental data. A set of reliable and self-consistent thermodynamic parameters were obtained combining with Mg–Sb and Mg–Al systems as well as the updated Al–Sb system in the present work. The solidification paths in Sb-containing Mg alloys were analyzed using the present thermodynamic description of Mg–Al–Sn–Sb quaternary system extrapolated from that of the constituent sub-ternary systems.

Tricritical point in the quantum Hamiltonian mean-field model.

Engineering long-range interactions in experimental platforms has been achieved with great success in a large variety of quantum systems in recent years. Inspired by this progress, we propose a generalization of the classical Hamiltonian mean-field model to fermionic particles. We study the phase diagram and thermodynamic properties of the model in the canonical ensemble for ferromagnetic interactions as a function of temperature and hopping. At zero temperature, small charge fluctuations drive the many-body system through a first-order quantum phase transition from an ordered to a disordered phase. At higher temperatures, the fluctuation-induced phase transition remains first order initially and switches to second-order only at a tricritical point. Our results offer an intriguing example of tricriticality in a quantum system with long-range couplings, which bears direct experimental relevance. The analysis is performed by exact diagonalization and mean-field theory.

Correction: Phase Equilibria and Thermodynamic Properties of Low Basicity RE-Contained Slags by Critical Evaluation and Experiment

Correction: Phase Equilibria and Thermodynamic Properties of Low Basicity RE-Contained Slags by Critical Evaluation and Experiment

Investigation of liquid n-heptane/air spray detonation with an Eulerian-Eulerian model

A two-dimensional numerical simulation of detonation in a reactive dispersed liquid droplet cloud is performed with an Eulerian-Eulerian method. This study aims to investigate the model and the effects of two-phase sub-models on the propagation of a detonation through an n-heptane spray. Firstly, the simulations are compared to the experiments conducted in the thesis of Mohamed El-Amine Benmahammed [1]. Three simulations are carried out for a mono-dispersed/one sample cloud of droplets with a mass corresponding to equivalence ratios of 0.8, 1.0, and 1.3. The Eulerian-Eulerian method predicted the experimental detonation velocity and gaseous phase thermodynamic properties with reasonable accuracy. Secondly, an investigation of the effects of the mobilization of the droplet size poly-dispersity on the detonation properties was carried out. For a droplet Sauter mean diameter of 30 µm, the effect of the number of droplet samples used for modeling the poly-dispersity modifies the front structure and detonation properties. For instance, comparing 15 samples of droplet size to a unique sample, the detonation velocity decreases by 2.0 %, and the mean detonation cell width increases by 10 %.

Experimental study and thermodynamic assessment of thermodynamic properties of pure Li2CO3 and K2CO3

In this work, the thermodynamic properties (heat capacity, transition temperature) and structure of Li2CO3 and K2CO3 were investigated experimentally using Differential Thermal Analysis (DTA), different types of Differential Scanning Calorimetry (DSC) and high temperature X-ray diffraction (HTXRD). The controversial solid-solid phase transition of Li2CO3 was proved to be caused by impurities. The accuracy of the heat capacity for both carbonates was improved. The Gibbs energy data of these carbonates were reassessed in the new database, which can improve the accuracy in calculating and predicting the phase equilibria and thermodynamic properties in the corresponding multiple salt systems.

Phase Equilibria and Thermodynamic Properties of Low Basicity RE-Contained Slags by Critical Evaluation and Experiment

Phase Equilibria and Thermodynamic Properties of Low Basicity RE-Contained Slags by Critical Evaluation and Experiment

Evolution of the structure and properties of (Zr1-xHfx)B2 solid solution ceramics from first-principle theory

As typical ultra-high temperature ceramics, both ZrB2 and HfB2 have unique properties such as excellent mechanical performance and oxidation resistance, are promising candidates for the aerospace industry. In this work, the phase stability, electronic, mechanical and thermodynamic properties of (Zr1-xHfx)B2 solid solution ceramics were systematically studied performing by first-principles calculations. The calculated results of structural optimization and elastic constants are in good agreement with the experimental values, which confirms the reliability of the proposed model. The lattice parameters of the optimized (Zr1-xHfx)B2 solid solution ceramics are linearly related to the Hf content, while a decrease is detected as the increasing Hf content. The calculated elastic constants show that the addition of Hf is beneficial in improving the mechanical properties of the (Zr1-xHfx)B2 solid solution, including the elastic modulus, hardness and fracture toughness. In addition, the (Zr1-xHfx)B2 solid solution was found to be kinetically stable. From the trend of the calculated value of the Debye temperature, it can be found that the addition of Hf can effectively reduce the thermal conductivity of solid solution materials. Our work introduced an important theoretical framework, which is of great significance for the development of solid solution diboride material systems with adjustable composition and properties.

Phase diagram and thermodynamic properties of the frustrated ferro-antiferromagnetic spin system on the octahedral lattice

The influence of anisotropy generated by the competition between the ferromagnetic and antiferromagnetic nearest-neighbor interactions on the magnetic and thermodynamic properties of the classical spin system on the octahedral lattice is investigated in the framework of the exactly solvable Ising-like model on the recursive octahedral lattice. The phase diagram of the model is found and the nature of all phase transitions is determined. It is shown that the model exhibits the existence of the intermediate phase that separates the ferromagnetic phase from the antiferromagnetic one. Moreover, it is also shown that while the intermediate phase and the antiferromagnetic one are separated by the critical curve of the second-order phase transitions the transitions between the ferromagnetic phase and the intermediate one have the first-order nature on the coexistence line. The magnetization and entropy properties of all phases of the model are studied. Depending on the value of the frustration parameter, four different ground states are identified with formation of a strict residual entropy hierarchy. Due to the frustration nature of the model the specific heat capacity exhibits anomalous (Schottky) behavior at low temperatures in the vicinity of the value of the frustration parameter, for which two highly macroscopically degenerated single-point-like ground states are formed. The presence of the intermediate phase in the model also leads to the existence of the series of even three successive second-order phase transitions in the temperature dependence of the magnetization as well as of the specific heat capacity.

First-principles calculations and thermodynamic assessment of the Nb–V system using CE-CVM

A thermodynamic assessment of the Nb–V system has been carried out based on first-principles calculations and all the available experimental thermodynamic and phase equilibria data. Mixed-parametric ab initio calculations were performed to calculate the enthalpy of mixing data with Special quasirandom structures (SQS) and cluster expansion (CE) method. The Gibbs energy of the bcc solid phase was described using tetrahedron approximation of the Cluster Expansion and Cluster Variation Methods (CE-CVM). A sub-regular solution model was used for describing Gibbs energy of the liquid phase. An optimal set of parameters has been obtained for describing the Gibbs energies of the liquid and solid phases in the Nb–V binary system. The calculated phase diagram and thermodynamic properties agree with experimental data. The relevance of CE-CVM has been demonstrated in the present case by calculating the solid phase's short-range order (sro) parameters as a function of composition and temperature.

Structures, phase transitions, thermodynamic properties, and structural dynamics of eco-friendly hybrid perovskite NH3(CH2)3NH3CoCl4 and NH3(CH2)5NH3CoCl4 crystals

The present study investigates the structures, phase transition temperatures, thermodynamic properties, and structural dynamics of the organic–inorganic perovskite NH3(CH2)nNH3CoCl4 (n = 3 and 5) crystals according to the number of carbon atoms. The structure and lattice constants were confirmed by single-crystal X-ray diffraction (XRD) at 298 K. From differential scanning calorimetry and XRD powder patterns, the phase transition temperature TC obtained at 483 K for n = 3 was isostructural without changing the crystal structure, whereas the TC for n = 5 was obtained at 494 K with change in the crystal structure. The thermodynamic properties of the two crystals studied by thermogravimetric analysis exhibited relatively high thermal stability at 600 K. From the spin-lattice relaxation times (T1ρ) according to the temperature change for n = 3 and 5, it was determined that the energy transfer, demonstrating a small thermal displacement around the 1H and 13C atoms of the cation, was minuscule. The effects of T1ρ for 1H and 13C were insignificant, indicating a minor change in the N–H⋯Cl hydrogen bond related to the coordination geometry of the CoCl4 anion. Thus, the obtained results for NH3(CH2)nNH3CoCl4 (n = 3 and 5) can be helpful for future research on the application of eco-friendly organic–inorganic hybrid perovskite materials.

Phase transitions in the frustrated Potts model in the magnetic field

The influence of the magnetic field on phase transitions, magnetic and thermodynamic properties of the two-dimensional Potts model with q = 4 on a hexagonal lattice with the nearest and next-nearest neighbors interactions is studied using the replica algorithm of the Monte Carlo method . The studies are carried out in the magnetic field range −1.0 ≤ h ≤ 7.0 with a step of 0.1. A phase diagram of the magnetization dependence on magnetic field value is plotted. It is found that a first-order phase transition is observed in the ranges 0.0 ≤ h ≤ 1.0 and 2.0 ≤ h ≤ 3.5. A second-order phase transition is observed for the magnetic field value h = 1.5. It is revealed that there is no the ground-state degeneracy and the phase transition is smeared for magnetic field values of h ≥ 4.0. A phase diagram of the dependence of the critical temperature on the magnitude of the interaction of the next-nearest neighbors is constructed. • A two-dimensional frustrated Potts model are investigated. • The magnetic structures of the ground-state for considered model are obtained. • The phase diagram is plotted. • It is shown that magnetic fields destroyed the phase transition.

Critical evaluation and thermodynamic optimization of the Si-N, Si-C, C-N and Si-C-N systems and its applications to high purity SiC production

Thermodynamic optimization of the Si-N, Si-C, C-N and Si-C-N systems were performed using the CALculation of PHAse Diagrams (CALPHAD) method based on critical evaluation of all available experimental data. The liquid and solid solutions within the Si-C-N system were described using the Modified Quasichemical Model and Compound Energy Formalism, respectively. The Gibbs energies of β-Si3N4 and β-SiC were carefully optimized to resolve inconsistencies among existing thermodynamic properties and phase equilibria data. The solubilities of C and N in both solid and liquid Si solutions were critically optimized. Besides, the solubility of N in β-SiC to form a narrow homogeneity range of β-Si(C,N) solid solution is considered for the first time in the present thermodynamic modeling. Based on the present thermodynamic database, experimentally unexplored phase diagrams and thermodynamic properties within the Si-C-N alloys were predicted. As an application of the database, the influences of various operation conditions on high purity SiC production using sublimation process were calculated.

Phase State and Thermodynamic Properties of Proxy Sea Spray Aerosol Interfaces Derived from Temperature-Dependent Equilibrium Spreading Pressure

Phase State and Thermodynamic Properties of Proxy Sea Spray Aerosol Interfaces Derived from Temperature-Dependent Equilibrium Spreading Pressure

Phase diagram study and thermodynamic assessment of the Y2O3-YF3 system

The phase diagram of the Y2O3-YF3 system up to 1973 K was investigated using a classical equilibration/quenching experiment and differential thermal analysis (DTA). Equilibrium phases were confirmed by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) phase analysis. For the very first time, the entire range of the phase diagram of yttrium oxy-fluoride system up to 1973 K was experimentally determined. Cubic-Y2O3 phase dissolves more than 5 mol% of YF3 at 1973 K. The melting points of YOF and vernier phases are found to be higher than 1973 K and their steep liquidus in the YF3-rich region are determined. Based on new experimental phase diagram data and thermodynamic property data in the literature, the Y2O3-YF3 system was thermodynamically modeled by the CALculation of PHAse Diagram (CALPHAD) method. As applications of the thermodynamic database, metastable solubilities of YF3 in Y2O3 during plasma etching process were calculated.

Ideal Gas Heat Capacity and Critical Properties of HFE-Type Engineering Fluids: Ab Initio Predictions of Cpig, Modeling of Phase Behavior and Thermodynamic Properties Using Peng–Robinson and Volume-Translated Peng–Robinson Equations of State

Ideal Gas Heat Capacity and Critical Properties of HFE-Type Engineering Fluids: Ab Initio Predictions of Cpig, Modeling of Phase Behavior and Thermodynamic Properties Using Peng–Robinson and Volume-Translated Peng–Robinson Equations of State

Phase transformations and thermodynamic properties of oxide systems

A new approach to obtain amorphous oxides was investigated both theoretically and experimentally using X-ray diffraction (XRD) and electron probe microanalysis (EPMA) techniques. In this work, the conventional sol-gel method was modified by the addition of malic acid as an oxidizing agent and successfully applied to obtain two oxides Al2O3 & Fe2O3 with the amorphous structure. The results of the modified sol-gel method were compared to those obtained by thermal decomposition of corresponding salts, and the advantage of new technique was clearly demonstrated. Thermal stability of the obtained amorphous oxides was examined by the differential scanning calorimetry (DSC). It was found that amorphous Al2O3 is stable up to 790 – 810 °C, while amorphous Fe2O3 recrystallises at about 160 – 180 °C, depending on the heating rate.

Harnessing Deep Learning for Optimization of Lennard-Jones Parameters for the Polarizable Classical Drude Oscillator Force Field.

The outcomes of computational chemistry and biology research, including drug design, are significantly influenced by the underlying force field (FF) used in molecular simulations. While improved FF accuracy may be achieved via inclusion of explicit treatment of electronic polarization, such an extension must be accompanied by optimization of van der Waals (vdW) interactions, in the context of the Lennard-Jones (LJ) formalism in the present study. This is particularly challenging due to the extensive nature of chemical space combined with the correlated nature of LJ parameters. To address this challenge, a deep learning (DL)-based parametrization framework is developed, allowing for sampling of wide ranges of LJ parameters targeting experimental condensed phase thermodynamic properties. The present work utilizes this framework to develop the LJ parameters for atoms associated with four distinct groups covering 10 different atom types. Final parameter selection was facilitated by quantum mechanical data on rare-gas interactions with the training set molecules. The chosen parameters were then validated through experimental hydration free energies and condensed phase thermodynamic properties of validation set molecules to confirm transferability. The ultimate outcome of utilizing this framework is a set of LJ parameters in the context of the polarizable Drude FF, which demonstrated improvement in the reproduction of both experimental pure solvent and crystal properties and hydration free energies of the molecules compared to the additive CHARMM General FF (CGenFF) including the ability of the Drude FF to accurately reproduce both experimental pure solvent properties and hydration free energies. The study also shows how correlations between difference in the reproduction of condensed phase data between model compounds may be used to direct the selection of new atom types and training set molecules during FF development.