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Large-scale molecular dynamics (MD) simulations enabled by computationally efficient semiempirical potentials are an invaluable tool for materials modeling. In the case of metallic alloys, embedded atom method (EAM) and Finnis–Sinclair (FS) potentials are a reasonable choice based on their good balance of quality and computational cost. However, these semiempirical potentials are not suitable for simulating ionic systems, which prevents their use in studying many technologically relevant metal–oxide systems. The charge transfer ionic potential (CTIP), which can utilize EAM/FS potentials available in the literature together with a variable charge representation of electrostatic interactions, should be a reasonable choice for performing reliable and computationally efficient MD simulations of such systems. However, only a few such potentials are available in the literature, and their computational cost is much higher compared to EAM/FS potentials. In the present work, we have attempted to remedy these deficiencies by combining several modifications to the CTIP model proposed in the literature and efficiently implementing them into the widely used Large-scale Atomic/Molecular Massively Parallel Simulator MD code. Using these modifications, we have developed a new Ni–O CTIP parameterization, which has been tested in several different scenarios of interest. First, the early stages of Ni surface oxidation were simulated, demonstrating the nucleation and growth of a crystalline NiO film across the surface. Second, solidification and vitrification in the Ni–O system were investigated, demonstrating that the new CTIP parameterization provides reasonable agreement with the experimentally determined equilibrium phase diagram. Finally, we studied the interaction of dislocations in a Ni matrix with a NiO inclusion using a simulation cell with an unprecedented number of atoms for a variable charge MD simulation. Thus, the approach utilized in the present study is an efficient method to simulate large scale atomic mechanisms in metal–oxide systems. [ABSTRACT FROM AUTHOR]

We explore the solubilities of guest CH4 and/or CO2 in the aqueous state coexisting with the corresponding hydrate. The equilibrium conditions are estimated by calculating the chemical potentials of water and guest species in the hydrate on the basis of a statistical mechanical theory using pairwise intermolecular potentials. This requires the least computational cost while covering a wide range of temperature, pressure, and composition of guest species, even for the binary hydrate. The nonstoichiometric nature, one of the most important characters of hydrates, is invariably taken into account when evaluating its phase behaviors and the driving force for nucleation of hydrates. The two-phase equilibrium concerning CO2 hydrate is evaluated considering a low but finite value of CO2 solubility in water. It is found that the finite solubility gives rise to a small systematic deviation of the dissociation temperature of CO2 hydrate. The solubility of CO2 coexisting with fluid CO2 decreases with temperature but the opposite temperature dependence is obtained in the presence of hydrate, as in the case of CH4. This method is applied to CH4–CO2 binary hydrates of various guest compositions. We also find a significant difference in composition of guests among the phases involved in the equilibria. [ABSTRACT FROM AUTHOR]

FEASST is an open-source Monte Carlo software package for particle-based simulations. This software, which was released in 2017, has been used to study phase equilibrium, self-assembly, aggregation or gelation in biological materials, colloids, polymers, ionic liquids, and adsorption in porous networks. We highlight some of the unique features available in FEASST, such as flat-histogram grand canonical ensemble, Gibbs ensemble, and Mayer-sampling simulations with support for anisotropic models and parallelization with flat-histogram and prefetching. We also discuss how the challenges of supporting a variety of Monte Carlo algorithms were overcome by an object-oriented design. This also allows others to extend classes, which improves software interoperability, as inspired by LAMMPS classes and user packages. This article describes version 0.25.1 with benchmarks, compilation instructions, and introductory tutorials for running, restarting, and testing simulations, user guidelines, software design strategies, alternative interfaces, and the test-driven development strategy. [ABSTRACT FROM AUTHOR]

Thin-film confinement of self-assembling block polymers results in materials with myriad potential applications—including membranes and optical devices—and provides design parameters for altering phase behavior that are not available in the bulk, namely, film thickness and preferential wetting. However, most research has been limited to lamella- and cylinder-forming polymers; three-dimensional phases, such as double gyroid (DG), have been observed in thin films, but their phase behavior under confinement is not yet well understood. We use self-consistent field theory to predict the equilibrium morphology of bulk-gyroid-forming AB diblock polymers under thin-film confinement. Phase diagrams reveal that the (211) orientation of DG, often observed in experiments, is stable between nonpreferential boundaries at thicknesses as small as 1.2 times the bulk DG lattice parameter. The (001) orientation is stable between modestly B-preferential boundaries, where B is the majority block, while a different (211)-oriented termination plane is stabilized by strongly B-preferential boundaries, neither of which has been observed experimentally. We then describe two particularly important phenomena for explaining the phase behavior of DG thin films at low film thicknesses. The first is "constructive interference," which arises when distortions due to the top and bottom boundaries overlap and is significant for certain DG orientations. The second is a symmetry-dependent, in-plane unit-cell distortion that arises because the distorted morphology near the boundary has a different preferred unit-cell size and shape than the bulk. These results provide a thermodynamic portrait of the phase behavior of DG thin films. [ABSTRACT FROM AUTHOR]

By employing non-equilibrium molecular dynamics (NEMD) simulations and time-dependent Ginzburg–Landau (TDGL) theory for solidification kinetics [Cryst. Growth Des. 20, 7862 (2020)], we predict the kinetic coefficients of FCC(100) crystal–melt interface (CMI) of soft-spheres modeled with an inverse-sixth-power repulsive potential. The collective dynamics of the local interfacial liquid phase at the equilibrium FCC(100) CMIs are calculated based on a recently proposed algorithm [J. Chem. Phys. 157, 084 709 (2022)] and are employed as the resulting parameter that eliminates the discrepancy between the predictions of the kinetic coefficient using the NEMD simulations and the TDGL solidification theory. A speedup of the two modes of the interfacial liquid collective dynamics (at wavenumbers equal to the principal and the secondary reciprocal lattice vector of the grown crystal) is observed. With the insights provided by the quantitative predictive theory, the variation of the solidification kinetic coefficient along the crystal–melt coexistence boundary is discussed. The combined methodology (simulation and theory) presented in this study could be further applied to investigate the role of the inter-atomic potential (e.g., softness parameter s = 1/n of the inverse-power repulsive potential) in the kinetic coefficient. [ABSTRACT FROM AUTHOR]

The phase separation of protein and RNA mixtures underpins the assembly and regulation of numerous membraneless organelles in cells. The ubiquity of protein–RNA condensates in cellular regulatory processes is in part due to their sensitivity to RNA concentration, which affects their physical properties and stability. Recent experiments with poly-cationic peptide–RNA mixtures have revealed closed-loop phase diagrams featuring lower and upper critical solution temperatures. These diagrams indicate reentrant phase transitions shaped by biomolecular interactions and entropic forces such as solvent and ion reorganization. We employed atomistic simulations to study mixtures with various RNA–polylysine stoichiometries and temperatures to elucidate the microscopic driving forces behind reentrant phase transitions in protein–RNA mixtures. Our findings reveal an intricate interplay between hydration, ion condensation, and specific RNA–polylysine hydrogen bonding, resulting in distinct stoichiometry-dependent phase equilibria governing stabilities and structures of the condensate phase. Our simulations show that reentrant transitions are accompanied by desolvation around the phosphate groups of RNA, with increased contacts between phosphate and lysine side chains. In RNA-rich systems at lower temperatures, RNA molecules can form an extensive pi-stacking and hydrogen bond network, leading to percolation. In protein-rich systems, no such percolation-induced transitions are observed. Furthermore, we assessed the performance of three prominent water force fields—Optimal Point Charge (OPC), TIP4P-2005, and TIP4P-D—in capturing reentrant phase transitions. OPC provided a superior balance of interactions, enabling effective capture of reentrant transitions and accurate characterization of changes in solvent reorganization. This study offers atomistic insights into the nature of reentrant phase transitions using simple model peptide and nucleotide mixtures. We believe that our results are broadly applicable to larger classes of peptide–RNA mixtures exhibiting reentrant phase transitions. [ABSTRACT FROM AUTHOR]

Liquid–liquid phase separation in biology has recently been shown to play a major role in the spatial control of biomolecular components within the cell. However, as they are phase transitions, these processes also display nontrivial dynamics. A model phase-separating system of DNA nanostars provides unique access to nucleation physics in a biomolecular context, as phase separation is driven near room temperature by highly thermo-responsive DNA hybridization and at modest DNA concentrations. By measuring the delay time for phase-separated droplets to appear, we demonstrate that the dynamics of DNA nanostar phase separation reflect that of a metastable binary mixture of patchy particles. For sufficiently deep temperature quenches, droplets undergo spinodal decomposition and grow spontaneously, driven by Brownian motion and coalescence of phase-separated droplets, as confirmed by comparing experimental measurements to particle-based simulations. Near the coexistence boundary, droplet growth slows substantially, indicative of a nucleation process. The temperature dependence of droplet appearance times can be predicted by a classical nucleation picture with mean field exponents and demonstrates that a theory previously used to predict equilibrium phase diagrams can also distinguish spinodal and nucleation dynamical regimes. These dynamical principles are relevant to behaviors associated with liquid–liquid phase separating systems, such as their spatial patterning, reaction coupling, and biological function. [ABSTRACT FROM AUTHOR]

The isothermal compressibility (i.e., related to the asymptotic number variance) of equilibrium liquid water as a function of temperature is minimal under near-ambient conditions. This anomalous non-monotonic temperature dependence is due to a balance between thermal fluctuations and the formation of tetrahedral hydrogen-bond networks. Since tetrahedrality is a many-body property, it will also influence the higher-order moments of density fluctuations, including the skewness and kurtosis. To gain a more complete picture, we examine these higher-order moments that encapsulate many-body correlations using a recently developed, advanced platform for local density fluctuations. We study an extensive set of simulated phases of water across a range of temperatures (80–1600 K) with various degrees of tetrahedrality, including ice phases, equilibrium liquid water, supercritical water, and disordered nonequilibrium quenches. We find clear signatures of tetrahedrality in the higher-order moments, including the skewness and excess kurtosis, which scale for all cases with the degree of tetrahedrality. More importantly, this scaling behavior leads to non-monotonic temperature dependencies in the higher-order moments for both equilibrium and non-equilibrium phases. Specifically, under near-ambient conditions, the higher-order moments vanish most rapidly for large length scales, and the distribution quickly converges to a Gaussian in our metric. However, under non-ambient conditions, higher-order moments vanish more slowly and hence become more relevant, especially for improving information-theoretic approximations of hydrophobic solubility. The temperature non-monotonicity that we observe in the full distribution across length scales could shed light on water's nested anomalies, i.e., reveal new links between structural, dynamic, and thermodynamic anomalies. [ABSTRACT FROM AUTHOR]

O and Nb are two representative alloying elements of Ti to form high-temperature and corrosion resistance α Ti alloys. The investigation on the thermodynamic characteristics of α Ti–O and Ti–Nb has attracted much attention in recent years. However, in this regard, a satisfied experimental technique or modeling scheme is still yet to be developed due to the appearance of a variety of oxides in Ti–O and the mechanical instability present in Ti–Nb. Herein, we combined first-principles calculations with the cluster expansion method to investigate the ground-state characteristics for α Ti–O and α Ti–Nb systems. The atomic bonding interactions in these two systems were first revealed based on the calculated electronic structures. Afterward, the Debye–Grüneisen model and Monte Carlo simulations were employed together to investigate the thermodynamic properties of α phases in these two systems, and the effect of vibrational entropy on the order–disorder transition temperatures of the phases in α Ti–O system was first examined. A good agreement with experimentally reported phase boundaries is obtained in the Ti–Nb system by handling the mechanical instabilities introduced by the highly distorted structures. In addition, the cluster expansion coefficients for the Ti–O and Ti–Nb system offer a good starting point to investigate the phase equilibrium in Ti–Nb–O ternary alloy. We also believe the insights provided here would be helpful for those who would like to seek an efficient scheme they are confident with to investigate the phase thermodynamic properties of other hcp Ti-based alloys. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been devoted to understanding the pathways of phase transition between two equilibrium condensed phases (such as liquids and solids). However, the microscopic pathways of transition involving non-equilibrium, non-diffusive amorphous (glassy) phases still remain poorly understood. In this work, we have employed computer simulations, persistence homology (a tool rooted in topological data analysis), and machine learning to probe the microscopic pathway of pressure-induced non-equilibrium transition between the low- and high-density amorphous (LDA and HDA, respectively) ice phases of the TIP4P/2005 and ST2 water models. Using persistence homology and machine learning, we introduced a new order parameter that unambiguously identifies the LDA- and HDA-like local environments. The LDA phase transitions continuously and collectively into the corresponding HDA phase via a pre-ordered intermediate phase during the isothermal compression. The local order parameter susceptibilities show a maximum near the transition pressure (P*)—suggesting maximum structural heterogeneities near P*. The HDA-like clusters are structurally ramified and spatially delocalized inside the LDA phase near the transition pressure. We also found manifestations of the first-order low-density to high-density liquid transition in the sharpness of the order parameter change during the LDA to HDA transition. We further investigated the (geometrical) structures and topologies of the LDA and HDA ices formed via different protocols and also studied the dependence of the (microscopic) pathway of phase transition on the protocol followed to prepare the initial LDA phase. Finally, the method adopted here to study the phase transition pathways is not restricted to the system under consideration and provides a robust way of probing phase transition pathways involving any two condensed phases at both equilibrium and out-of-equilibrium conditions. [ABSTRACT FROM AUTHOR]

Clathrate hydrates are vital in energy research and environmental applications. Understanding their stability is crucial for harnessing their potential. In this work, we employ direct coexistence simulations to study finite-size effects in the determination of the three-phase equilibrium temperature (T3) for methane hydrates. Two popular water models, TIP4P/Ice and TIP4P/2005, are employed, exploring various system sizes by varying the number of molecules in the hydrate, liquid, and gas phases. The results reveal that finite-size effects play a crucial role in determining T3. The study includes nine configurations with varying system sizes, demonstrating that smaller systems, particularly those leading to stoichiometric conditions and bubble formation, may yield inaccurate T3 values. The emergence of methane bubbles within the liquid phase, observed in smaller configurations, significantly influences the behavior of the system and can lead to erroneous temperature estimations. Our findings reveal finite-size effects on the calculation of T3 by direct coexistence simulations and clarify the system size convergence for both models, shedding light on discrepancies found in the literature. The results contribute to a deeper understanding of the phase equilibrium of gas hydrates and offer valuable information for future research in this field. [ABSTRACT FROM AUTHOR]

The crystallization process of methane hydrates in a confined geometry resembling seabed porous silica sedimentary conditions has been studied using molecular dynamics simulations. With this objective in mind, a fully atomistic quartz silica slit pore has been designed, and the temperature stability of a methane hydrate crystalline seed in the presence of water and guest molecule methane has been analyzed. NaCl ion pairs have been added in different concentrations, simulating salinity conditions up to values higher than average oceanic conditions. The structure obtained when the hydrate crystallizes inside the pore is discussed, paying special attention to the presence of ionic doping inside the hydrate and the subsequent induced structural distortion. The shift in the hydrate stability conditions due to the increasing water salinity is discussed and compared with the case of unconfined hydrate, concluding that the influence of the confinement geometry and pore hydrophilicity produces a larger deviation in the confined hydrate phase equilibria. [ABSTRACT FROM AUTHOR]

This study reviews available van der Waals- and Platteeuw-based hydrate models considering multiple occupancy of cavities. Small guest molecules, such as hydrogen and nitrogen, are known to occupy lattice cavities multiple times. This phenomenon has a significant impact on hydrate stability and thermodynamic properties of the hydrate phase. The objective of this work is to provide a comprehensive overview and required correlations for the implementation of a computationally sufficient cluster model that considers up to five guest molecules per cavity. Two methodologies for cluster size estimation are evaluated by existing nitrogen hydrate models showing accurate results for phase equilibria calculations. Furthermore, a preliminary hydrogen hydrate model is introduced and compared with the results of other theoretical studies, indicating that double occupancy of small sII cavities is improbable and four-molecule clusters are predominant in large sII cavities for pressures above 300 MPa. This work lays the foundation for further exploration and optimization of hydrate-based technologies for small guest molecules, e.g., storage and transportation, emphasizing their role in the future landscape of sustainable energy solutions. [ABSTRACT FROM AUTHOR]

This study investigates the stability of chiral-molecule solution phases, with a specific focus on amino acids. The model framework is based on a two-dimensional square lattice model, where individual sites may be occupied by oriented chiral molecules or structureless solvent particles. Utilizing the Glauber dynamics and statistical mechanical formalism, as previously introduced and examined by Lombardo et al., we explore the influence of temperature, amino acid concentration, enantiomeric excess, and homochiral interaction strength on nucleation mechanisms, equilibrium phase behavior, and crystal composition. Our findings offer thermodynamic insights into the chiral amplification process of amino acids, contributing to a deeper understanding of the underlying processes. [ABSTRACT FROM AUTHOR]

The effect of ring stiffness and pressure on the glassy dynamics of a thermal assembly of two-dimensional ring polymers is investigated using extensive coarse-grained molecular dynamics simulations. In all cases, dynamical slowing down is observed with increasing pressure, and thereby, a phase space for equilibrium dynamics is identified in the plane of the obtained monomer density and ring stiffness. When the rings are highly flexible, i.e., have low ring stiffness, glassiness sets in via the crowding of crumpled polymers, which take on a globular form. In contrast, at large ring stiffness, when the rings tend to have large asphericity under compaction, we observe the emergence of local domains having orientational ordering at high pressures. Therefore, our simulations highlight how varying the deformability of rings leads to contrasting mechanisms in driving the system toward the glassy regime. [ABSTRACT FROM AUTHOR]

Mixing Gibbs energy and phase equilibria of aqueous solutions of polyglycine were studied theoretically by means of polymer reference interaction site model integral equation theory combined with the Gibbs–Duhem method. In addition to the ordinary liquid–liquid phase separation between dilute and concentrated solutions, the theoretical calculation predicted the coexistence of two coacervate phases, namely, the lower- and higher-density coacervates. The relative thermodynamic stabilities of these two phases change with the polymerization degree of polyglycine. The higher-density coacervate phase was rapidly stabilized by increasing the polymer length, and the lower-density phase became metastable at large polymers. The hydrogen bonds between the peptide chains were strengthened, and water was thermodynamically destabilized in the higher-density coacervate. A possible relation with the formation of amyloid fibril within a liquid droplet is also discussed. [ABSTRACT FROM AUTHOR]

Natural gas hydrates, mainly existing in permafrost and on the seabed, are expected to be a new energy source with great potential. The exploitation technology of natural gas hydrates is one of the main focuses of hydrate-related studies. In this study, a large-size liquid aqueous solution wrapping a methane hydrate system was established and molecular dynamics simulations were used to investigate the phase equilibrium conditions of methane hydrate at different methane concentrations and interfacial geometries. It is found that the methane concentration of a solution significantly affects the phase equilibrium of methane hydrates. Different methane concentrations at the same temperature and pressure can lead to hydrate formation or decomposition. At the same temperature and pressure, in a system reaching equilibrium, the size of spherical hydrate clusters is coupled to the solution concentration, which is proportional to the Laplace pressure at the solid–liquid interface. Lower solution concentrations reduce the phase equilibrium temperature of methane hydrates at the same pressure; as the concentration increases, the phase equilibrium temperature gradually approaches the actual phase equilibrium temperature. In addition, the interfacial geometry of hydrates affects the thermodynamic stability of hydrates. The spherical hydrate particles have the highest stability for the same volume. Through this study, we provide a stronger foundation to understand the principles driving hydrate formation/dissociation relevant to the exploitation of methane hydrates. [ABSTRACT FROM AUTHOR]

Megacrysts in kimberlite are large (>1 cm) mineral grains that crystallized from sub-lithospheric proto-kimberlite melts in the lower sub-continental lithospheric mantle (SCLM), often after complex melt-SCLM interactions. Understanding the development of the proto-kimberlite melt system is important for two primary reasons: 1) a control on the melt diversification and range in Mg# observed in kimberlites that erupt at the surface and 2) it is associated with diamond-destruction in the deep lithosphere. We present δ18O values for a well-characterized suite of megacrysts from the Monastery kimberlite, South Africa, to evaluate variations in melt δ18O, the effect of melt-SCLM interactions on the primary δ18O of mantle-derived magmas, and further constrain the development of the proto-kimberlite melt system in the deep lithosphere. The δ18O values of the megacrysts from the early-crystallising assemblages of Fe-poor (Mg# 83–88) olivine and relatively primitive (Group 1) ilmenite are: δ18O Fe-poor ol = 5.43 to 5.84 ‰ ( x ¯ = 5.23 ‰, σ = 0.10, n = 10); δ18O Grp 1 ilm = 3.88 to 4.35 ‰ ( x ¯ = 4.10 ‰, σ = 0.15, n = 8). The calculated δ18O value of melts in equilibrium with these megacrysts (5.4–5.8 ‰), indicates that they are typical of mantle-derived melts (i.e., 5.7 ± 0.2 ‰; Eiler, 2001). Garnet, clinopyroxene, and orthopyroxene have δ18O of: δ18O gt = 5.12 and 5.25 ‰ (n = 2); δ18O cpx = 4.72 and 5.02 ‰ (n = 2); δ18O opx = 5.20 and 5.55 ‰ (n = 2). The calculated melts in equilibrium with these phases range from 4.9 to 5.4 ‰, which overlaps those calculated for Fe-poor olivine and Group 1 ilmenite but extend to slightly lower δ18O. The δ18O values of the megacrysts from later crystallising assemblages of Fe-rich olivine (Mg# 78–83), moderately evolved (Group 2) ilmenite, phlogopite, and zircon have δ18O values are: δ18O Fe-rich ol = 4.53–4.94 ‰ ( x ¯ = 4.75 ‰, σ = 0.15, n = 5); δ18O Grp 2 ilm = 2.74–4.46 ‰ ( x ¯ = 3.56 ‰, σ = 0.45, n = 11); δ18O phlog = 4.25–5.73 ‰ ( x ¯ = 5.08 ‰, σ = 0.48, n = 8); and δ18O zir = 4.87–5.09 ‰ ( x ¯ = 4.98 ‰, σ = 0.08, n = 6). These phases have calculated equilibrium melts (3.8–5.6 ‰) predominantly below the typical mantle range. The δ18O values of the Group 3 ilmenites, representing the last stage of crystallisation, have δ18O Grp 3 ilm = 2.93–4.05 ‰ ( x ¯ = 3.59 ‰, σ = 0.36, n = 7). Based on the most primitive megacrysts (Fe-poor olivine and Group 1 ilmenite), we show that the Monastery proto-kimberlite melt had a mantle-like δ18O value of 5.61 ± 0.15 ‰ upon entering the SCLM. The magma then experienced several stages of evolution in the deep lithosphere. The lower-than-normal mantle δ18O values of melts in equilibrium with, the more evolved megacrysts, Fe-rich olivines, Group 2 ilmenites, phlogopites, and zircons can be explained by the assimilation of low-δ18O eclogitic material. An increased Cr# during evolution, marked by the Group 2 ilmenites, suggests additional assimilation of a Cr-rich peridotitic component. We present a three-step model for the Monastery proto-kimberlite involving fractional crystallisation along with complex open-system processes involving melt-SCLM interactions and show that the δ18O value of primary mantle-derived magmas can be significantly modified during ascent through the lithospheric mantle. Furthermore, assimilation of an eclogitic component in the deep lithosphere may contribute to the Fe-enrichment observed in megacryst-rich kimberlites globally. [ABSTRACT FROM AUTHOR]

In-situ glass crystallization provides a unique platform to create hybrid materials with improved performances for emerging photonics applications. Here we report the design of a glass ceramic embedded with Ca 2 MgSi 2 O 7 :Eu2+ akermanite under the guideline of CaO-MgO-SiO 2 phase equilibrium. The growth of the akermanite from ultrasmall spherical nanoparticles to highly orientated dendrites is experimentally controlled. Notably, the resulting orientated dendritic glass ceramic achieves high crystalline up to 90.1 % due to the homogeneous congruent crystallization, and transparency as result of the reduced light scattering. Thanks to metastable electric carriers trapping center with ideal trap depth of 0.52–0.70 eV, and sunlight excitable properties of the crystallized akermanite, as revealed by thermoluminescence technique, the developed glass ceramic exhibits impressive optical storage capability. This highly crystalline glass ceramic coupling with excellent optical properties and chemical/physical stability is of particular interests for a wide range of applications in the safety field and high security fluorescent anti-counterfeiting. [Display omitted] [ABSTRACT FROM AUTHOR]

Push-pull imines with strong electron donor group(s) display exceptional basicity in the gas phase. Most of them do not exhibit prototropic tautomerism, and gas-phase acid-base equilibria have been already well described and reviewed. Some questions remain for tautomeric systems, particularly for their uncommon forms. As shown by quantum-chemical calculations, some often-neglected tautomers display higher basicity than the thermodynamically favored forms. However, their participation in tautomeric mixtures being in equilibrium is negligible, and their basicity can be impossible to measure in the gas phase by the equilibrium method. During this work, we examined the gas-phase proton basicity for some acyclic and cyclic push-pull organic bases containing the tautomeric amidine or guanidine group. By quantum-chemical calculations, we confirmed the existence of very low amounts of rare tautomeric forms, in particular, those bearing a methylidene (=CH2) group. We also demonstrated that the alkyl derivatives of rare tautomers, being free of prototropy, can be good candidates as very strong push-pull C bases, i.e., bases protonated on the =CH2 group. [ABSTRACT FROM AUTHOR]

Phase equilibria in the ZrO2–YO1.5–NbO2.5 system were experimentally studied at 1300°C, and a comparison with the existing ZrO2–YO1.5–TaO2.5 (ZYTO) was conducted. Ternary fluorite phases on the Y:Nb > 1 side extend from binary ZrO2‐YO1.5 to YO1.5–NbO2.5 system, generating a continuous solid solution region. Furthermore, it was observed that three phases of M‐YNbO4, fluorite, and m‐ZrO2 were in equilibrium. On the Y:Nb < 1 side, two three‐phase equilibrium regions were measured, namely M‐YNbO4+m‐ZrO2+O‐Nb2Zr6O17 and h‐Nb2O5+O‐Nb2Zr6O17+M‐YNbO4. The tetragonal YNbO4 and ZrO2 phases both extend nearly along with Y:Nb = 1. The t‐ZrO2 phases with slightly lower stabilizer content were found to transform into their monoclinic polymorph during the cooling process. However, in the ZrO2–YNbO4 subsystem, the tetragonal ZrO2 was nontransformable due to larger YO1.5 and NbO2.5 co‐dopants, and the maximum solubility is about 18.1 mol%. Upon cooling, the tetragonal YNbO4 phase, even with the maximum ZrO2 content, is transformable to monoclinic form. The maximum solubility of ZrO2 in YNbO4 is determined to be about 20.7 mol%. Finally, the high‐temperature liquidus in the ZrO2–YNbO4 system was first determined based on the cooling traces, and a vertical section diagram was proposed for further speculation. A eutectic reaction of Liquid→YNbO4+ZrO2 was discovered, and the eutectic composition and temperature were measured as 39.2ZrO2–29.2YO1.5–31.6NbO2.5 and 1813°C. This study provides the basis for thermodynamic assessment of ZrO2–YO1.5–NbO2.5 and is valuable for the design and development of the ZrO2–YO1.5–NbO2.5‐based ceramic materials. [ABSTRACT FROM AUTHOR]

W–Sn deposits are primarily linked to peraluminous S-type granites, with elevated ore-metal contents attributed to fractional crystallization. We explore additional factors affecting the W–Sn endowment of granites, focusing on anatectic source and melt-residue equilibrium during anatexis. This study focuses on W–Sn ore-locality near Sirohi (NW India). We evaluate the effects of greisenization in the metapelitic country rocks, prior to using them as source rock for open-system phase equilibria modelling. The aim was to model the batch melting and accumulated fractional melting, and fractional crystallization, to assess their effects on the W–Sn budget of granitic melt. Modelling suggests that ~ 30–35% of metapelitic source rock partially melts, with muscovite and biotite dehydration reactions primarily contributing W and Sn. However, the metal contribution of these reactions, in terms of W/Sn ratio, is distinct. The batch melt (W: 10 ppm, Sn: 37 ppm) and accumulated fractional melt (W: 15 ppm, Sn: 50 ppm) differ slightly in their W and Sn contents. On the cooling path, fractional crystallization promotes an increase in ore-metal concentrations by seven- to ninefold. Upon fractionation, the granitic melt derived by accumulated fractional melting (W: 141 ppm, Sn: 455 ppm) is significantly enriched in ore metals compared to the one from batch melting (W: 92 ppm, Sn: 355 ppm). Compared to global average pelite, Sirohi metapelites, being chemically mature, show improved potential to generate a metal-fertile granitic melt. Results highlight the importance of recycled metasedimentary rocks that are pre-enriched in W and Sn prior to their anatexis, towards the metal fertility of S-type granites. [ABSTRACT FROM AUTHOR]

The high-pressure (HP) migmatitic paragneiss of the Beni Bousera metamorphic unit (BBMU) from the Beni Bousera Massif underwent granulite-facies metamorphism. They mainly consist of garnet, biotite, kyanite, sillimanite, cordierite, spinel, quartz, plagioclase, K-feldspar, rutile, ilmenite and graphite. These minerals form a sequence of metamorphic assemblages corresponding to five metamorphic events (M1, M2, M3, M4, and M5). The first three events correspond to a latest Carboniferous-earliest Permian metamorphic evolution, while the last two are retrograde and Alpine in age. The p-T conditions of these metamorphic events were estimated using pseudosection calculations in the MnNCKFMASTHO system. Following prograde stage conditions of 9.3–10.9 kbar and 630–665°C (M1 stage), the p-T evolution culminates in melting of the paragneiss which occurred mainly at HP conditions, within the kyanite stability field, at 11.8–14.2 kbar and 820–845°C (M2 pressure-peak); anatexis then continued at high to medium pressure (HMP), within the sillimanite stability field, at 9.9–11 Kbar and 840–860°C (M3 thermal-peak), accompanied by the production of very small proportions of melt. The prograde p-T segment of the inferred clockwise path is characterized by a pressurization related to a post-Variscan collisional event triggered by the closure of the Paleotethys Ocean, and is followed by the exhumation of the granulitic unit to mid-crustal depth, with slight coeval heating. The retrograde Alpine evolution is coeval with the final exhumation of the migmatitic paragneiss and underlying peridotites during back-arc extension related to the westward retreat of the Alpine subduction. It occurred under sub-solidus conditions from 9.5–10.7 kbar and 818–848°C (M4) to 4.9–5.85 kbar and 710–785°C (M5) and corresponds to a near-isothermal and strongly decompressive metamorphic evolution (ΔP ≈ 5 Kbar). [ABSTRACT FROM AUTHOR]

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The lack of thermodynamic data on vanadium slag, the main raw material for vanadium extraction, limits the efficient extraction of vanadium from vanadium slag. According to the composition and smelting process of industrial vanadium slag, this study firstly investigated the phase equilibria of the "FeO"–SiO2–CaO–16 wt pctV2O3 system at 1673 K and 1473 K under oxygen partial pressure of 10−10 atm via XRD, SEM and EPMA, based on which the phase diagrams of that at 1673 K and 1473 K were constructed. The results showed that the vanadium-enriched phases mainly consisted of V2O3, Fe2VO4, and Ca3[Fe,V]2(SiO4)3, where Ca3[Fe,V]2(SiO4)3 was generated due to the replacement of a large amount of Fe3+ by V3+ in Ca3Fe2(SiO4)3. On this basis, the phase relations of the "FeO"–SiO2–CaO–16 wt pctV2O3 system were further discussed. It was found that the decrease in temperature promoted the crystallization of Fe2VO4 and Ca3[Fe,V]2(SiO4)3, but had an inhibitory effect on the crystallization of V2O3. And Fe2VO4 was transformed to V2O3 or Ca3[Fe,V]2(SiO4)3 by decreasing Fe/Si (Mass fraction of "FeO" and SiO2). This study supplements the thermodynamic data for vanadium slag and provides a theoretical basis for the recovery of vanadium from vanadium slag. [ABSTRACT FROM AUTHOR]

The very low C content in interstitial-free (IF) steel is achieved through vacuum degassing and by adding Ti to Al-deoxidized molten steel during the steelmaking process. However, this low C content can lead to reoxidation, which, in turn, generates various oxide inclusions. Despite its significance, a comprehensive understanding of the evolution of these oxide inclusions has been hindered by the scarcity of fundamental information, such as phase equilibria in the relevant system. In this study, the thermodynamics and phase equilibria of the Fe-Al-Ti-O system, along with the evolution of oxide inclusions in the molten steel, were analyzed using various analytical techniques: CALculation of PHAse Diagrams (CALPHAD), scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and confocal scanning laser microscopy. High-temperature monitoring of oxide inclusion evolution through in-situ CSLM, SEM, and EBSD revealed that the primary constituents of the major oxide inclusions were alumina (corundum). Notably, (Ti, Al, Fe) 3 O 5 , exhibiting a pseudobrookite structure, was identified at higher O potentials, indicative of the reoxidation phenomena in molten steel. To advance the understanding of the stability of oxide inclusions in the molten steel at equilibrium, a self-consistent CALPHAD model was developed. This model provided insights into the stability and evolution of oxide inclusions within this system for the first time. It was demonstrated that the transition from alumina to (Ti, Al, Fe) 3 O 5 is influenced not only by the Al and Ti concentrations in the molten steel but also by the O content (or potential) within the system. The presence of (Ti, Al, Fe) 3 O 5 as an O carrier in molten steel adversely affects the steel's cleanliness. [ABSTRACT FROM AUTHOR]

The phase equilibria and division of the Ag2S–GaS–Ga2S3–FeS2–FeS–Ag2S region (A) of the Ag–Fe–Ga–S system below 600 K were established by the modified EMF method. The electrochemical cells (ECs) of the following structure were assembled: (−)C||Ag||SE||R(Ag+)||PE||C(+), where C is the graphite; Ag is the left electrode; SE is the solid-state electrolyte; PE is the right electrode; R(Ag+) is the region of Ag+ diffusion in the PE. Initially assembled PEs are a nonequilibrium phase mixture of binary sulfides with the ratios of simple substances covering all composition space of (A). The catalyst for the reactions in R(Ag+) were Ag+ ions acting as small nucleation centers of equilibrium mixtures of compounds. The division of (A) was realized with the participation of the binary as well as more complex compounds AgGaS2, Ag9GaS6, AgFeS2, Ag2FeS2, Ag2FeGa20S32, Ag2FeGa2S5, and Ag18Fe9Ga2S21. The spatial position of the three- and four-phase regions relative to the Ag point was employed to establish the overall potential-forming reactions for synthesizing quaternary phases in the PEs of ECs. The temperature dependencies of the electromotive force of ECs were used to calculate the values of the standard thermodynamic functions of the quaternary compounds. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a system of ordinary differential equations involving a non-autonomous Lotka-Volterra system of competition between the two species. Using the Taylor expansion, we consider the qualitative properties of the equilibrium points in the phase plane. Moreover, we examine the conditions for the persistence and extinction of the species. In addition, we show that the techniques used can be applied to a system of partial differential equations. Finally, we give numerical examples illustrated by the vector field around the equilibrium points to verify the theoretical results. [ABSTRACT FROM AUTHOR]

Vapor–liquid phase equilibrium (VLE) plays a crucial role in chemical process design, process equipment control, and experimental process simulation. However, experimental acquisition of VLE data is a challenging and complex task. As an alternative to experimentation, VLE data prediction offers great convenience and utility. In this article, an artificial intelligence network is proposed to predict the temperature and the vapor phase composition of binary mixtures. We constructed a graph neural network (GNN) and designed an uncertainty‐aware learning and inference mechanism (UALF) in the prediction process. The model was tested on both a self‐constructed dataset and a publicly available dataset. The results demonstrate that the proposed method effectively reveals the phase equilibrium properties of the target data. This work presents a novel approach for predicting vapor–liquid phase equilibrium in binary systems and proposes innovative ideas for investigating phase equilibrium mechanisms and principles. [ABSTRACT FROM AUTHOR]

Accurately predicting the phase behavior and properties of reservoir fluid plays an essential role in the simulation of petroleum recovery processes. Similar to the inaccurate liquid-density prediction issue in the isobaric-isothermal (PT) phase equilibrium calculations, an inaccurate pressure prediction issue can also be observed in isothermal-isochoric (VT) phase equilibrium calculations which involves a liquid phase. In this work, a practical methodology is proposed to incorporate a volume-translated equation of state in VT phase equilibrium calculations for more accurate pressure predictions. For this purpose, we adopt the state-of-art volume translation model recently proposed by Abudour et al. (Fluid Phase Equilib 349:37–55 2012, Fluid Phase Equilib 349:37–55, 2013). Single liquid phase calculations for 18 compounds and two hydrocarbon mixtures are conducted to demonstrate the soundness of the proposed methodology and evaluate the accuracy of pressure predictions. The calculated pressures by VT calculations with volume translated PR-EOS are compared to the actual pressures. The calculation results demonstrate that, by incorporating Abudour et al. (2012, 2013) volume translated PR-EOS models into the VT-based phase equilibrium calculation algorithm, the accuracy of pressure prediction in the single liquid phase region for both pure substances and mixtures can be significantly improved. Lastly, we apply the proposed algorithm to the two-phase VT phase equilibrium calculations for a ten-component oil sample MY10 which contains only normal alkanes. We numerically correct the pressure by applying the Abudour et al. VTPR-EOS to both the liquid phase and vapor phase. The pressures calculated by different phases become different. The pressures predicted based on the liquid phase are shifted downwards significantly, which leads to more accurate pressure predictions. To our knowledge, this issue is rarely investigated to incorporate the volume translation concept in VT phase equilibrium calculations. [ABSTRACT FROM AUTHOR]