Equations of state and thermoelastic properties of alkaline earth oxides at high pressures

Combining PC-SAFT equation of state with COSMO-SAC for vapor-liquid equilibrium prediction

• Ion-specific SAFT parameters were derived exclusively from pure-IL densities, with ion-solvent and ion-ion interactions modeled using a simplified Hudson-McCoubrey rule. • Six static permittivity approaches were evaluated within both SAFT-VRE Mie and eSAFT-VR Mie frameworks. • A novel Born size interpretation was introduced, explicitly accounting for hydrogen-bonding in ILs, showing direct correlation with SAFT parameters. • Incorporation of ionic effects improves the accuracy of SAFT-VR Mie in predicting densities of IL + water/methanol/ethanol mixtures. We evaluate the performance of two electrolyte variants of the Statistical Associating Fluid Theory for Variable Range interactions (SAFT-VR) in the generic Mie form, the SAFT-VRE Mie and eSAFT-VR Mie equations of state, in predicting liquid-phase densities and the speed of sound for imidazolium-based ionic liquids (ILs) and their mixtures with water, methanol, and ethanol. A strictly predictive modeling strategy was employed: only pure-component IL densities were used to derive ion-specific molecular parameters (segment length, size, and energy) for imidazolium-based cations and anions, while solvent parameters were taken from the literature. Ion-solvent and ion-ion pair interactions were calculated via a simplified Hudson-McCoubrey combining rule, assuming equal ionization potentials and avoiding any binary parameter fitting. Six formulations of the relative static permittivity (constant, temperature‐dependent, linear in composition, and a volumetric‐composition model) were evaluated within both the SAFT-VRE Mie and eSAFT-VR Mie frameworks. We introduce a novel Born size interpretation that explicitly accounts for hydrogen‐bonding in IL ions, yielding improved agreement with experimental data. Furthermore, we identify quantitative correlations between these Born size and the underlying SAFT parameters, enabling predictive parametrization of related IL systems. The electrolyte models enhance performance over the SAFT-VR Mie, particularly in mixed‐solvent regions, though further refinement is needed near the pure‐IL limit. All calculations were conducted using the open‐source Clapeyron.jl toolkit, ensuring full reproducibility and extensibility.

An evaluation approach for RP-3 surrogate fuels combining the PC-SAFT equation of state and residual entropy scaling

The article discusses the potential use of 3,3,3-trifluoropropene (R1243zf), a new refrigerant with zero ozone-depleting potential and a very low (0.29) global warming potential. In recent years, reliable experimental information has been obtained on the thermodynamic properties (density, pressure, isochoric heat capacity, and speed of sound) of R1243zf both in the single-phase region and on the liquid-vapor saturation line. Using the values of these thermodynamic quantities obtained over a wide range of state parameters, a series of equations of state for this refrigerant have been developed. In contrast to the known equations of state, a unified fundamental equation of state is proposed in this study. The unified fundamental equation of state for R1243zf is developed within the framework of a large-scale theory of critical phenomena and the similarity relation, which makes it possible to obtain reliable data on the equilibrium properties of liquid and gas not only in the regular part of the thermodynamic surface, but also in the asymptotic neighborhood of the critical point. A unified fundamental equation of state was used to calculate the standard reference data, including information on the density, pressure, enthalpy, entropy, speed of sound, isobaric and isochoric heat capacity of 3,3,3-trifl uoropropene in the range of state parameters of 169–420 K and up to 40 MPa. To estimate the uncertainty of the standard reference data, two methods based on the calculation of various statistical characteristics were used. The expanded uncertainties of the following equilibrium properties of R1243zf were obtained: density (0.25 %); pressure (0.35 %); specific heat capacity (1.2 %); speed of sound (0.37 %); saturated vapor and liquid density (0.55 and 0.40 %, respectively). The calculated estimates of the statistical characteristics indicate that the unified fundamental equation of state adequately conveys the equilibrium properties of the refrigerant R1243zf in the above-mentioned range of state parameters. The results of the study can be used in the design of air conditioning and refrigeration systems.

Guangqi: A 2D Radiation Hydrodynamic Code with Realistic Equations of State

Abstract In the framework of Loop Quantum Cosmology, we study a cosmological bouncing model with two fields that reproduce the desired features of the primordial power spectra. The model combines the matter-bounce mechanism, that generates scale-invariant perturbations, with ekpyrotic contraction, that suppresses anisotropies leading to the bounce. The bounce that replaces the classical initial singularity is achieved thanks to the loop quantisation. The matter-bounce is enacted by a quasi-dust scalar field, with a slightly-negative equation of state that accounts for a small positive cosmological constant, that generates a red-tilt in the perturbations' power spectra. A second field, endowed with an ekpyrotic potential, is introduced to tame the growth of anisotropies throughout the bouncing phase. The equations of motion of the scalar perturbations are non-trivially coupled, leading to rich phenomenology that cannot be inferred simply from their single-field counterpart. We study the evolution of scalar and tensor perturbations and compare the results to current observations, showing the viability of this model as a base for further investigations.

Abstract We consider the problem of a charged impurity exerting a weak, slowly decaying force on its surroundings, treating the latter as an ideal compressible fluid. In the semiclassical approximation, the ion is described by the Newton equation coupled to the Euler equation for the medium. After linearization, we obtain a simple closed formula for the effective mass of the impurity, depending on the interaction potential, the mean medium density, and sound velocity. Thus, once the interaction and the equation of state of the fluid is known, an estimate of the hydrodynamic effective mass can be quickly provided. Going beyond the classical case, we show that replacing the Newton with Schr"{o}dinger equation induces a different mass renormalization, wherein the surroundings affect the dynamics of the dispersion of the particle's wave packet. The two effective masses may remarkably differ, as, in particular, the scaling of the two Fermi polaron effective masses with the medium density is opposite. Our results are relevant for experimental systems featuring low energy impurities in Fermi or Bose systems, such as ions immersed in neutral atomic gases.

Supercritical CO 2 (SCO 2 ) centrifugal compressors are pivotal components in next-generation high-efficiency power cycles (e.g., Brayton cycles), enabling greater than 50% thermal efficiency and compact power block designs essential for sustainable energy systems. This study addresses a critical reliability challenge by optimizing dry gas seal (DGS) groove designs for these compressors. Using validated 3D CFD simulations, incorporating k-ω SST turbulence model and Redlich-Kwong real gas equation of state, the performance of four industrial groove geometries (spiral, oval, fish-tail, and tree-type) are evaluated. Results demonstrate that the tree groove minimizes leakage (29.7% reduction vs. spiral) through tortuous flow paths, directly supporting emissions control and operational economy in power cycles. Conversely, spiral grooves maximize opening force and gas film stiffness (6.2% higher stiffness vs. tree), ensuring stable non-contact operation crucial for compressor reliability at extreme pressures. Oval and fish-tail grooves offer intermediate trade-offs. Thermal analysis reveals considerable localized high temperature zones due to viscous dissipation and adiabatic compression, a key consideration for material longevity. This work establishes that groove selection fundamentally balances leakage rate (optimized by tree grooves) against hydrodynamic stability (maximized by spiral grooves). These findings provide practical guidelines for enhancing DGS performance in SCO 2 compressors, directly contributing to the viability of high-efficiency, low-emission power generation.

Machine-learned quantum molecular dynamics calculations of warm dense equation of state and ionic transport coefficients of deuterated water

In this work, we study a vector dark energy (vDE) model within the framework of a flat Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime. By using the Noether symmetry approach, we obtain analytical cosmological solutions. The vDE model includes a vector field [Formula: see text] coupled to gravity through an arbitrary coupling function [Formula: see text] and a potential function [Formula: see text], which are determined by imposing Noether symmetry conditions. These conditions yield specific forms for the coupling and potential functions, enabling the simplification of the dynamical system. By introducing new variables [Formula: see text] and [Formula: see text], we solve the field equations and obtain exact solutions for the scale factor [Formula: see text] and the vector field parameter [Formula: see text]. In this paper, we adopt the potential function in the form [Formula: see text] and derive solutions for general [Formula: see text]. We specifically examine the cases [Formula: see text] and [Formula: see text], which produce physically viable results consistent with late-time cosmic acceleration. Graphical representations of the scale factor, vector field parameter, and equation of state demonstrate the transition from a matter-dominated era to an accelerated expansion phase, with the equation of state approaching [Formula: see text], resembling a cosmological constant. This paper suggests that the vDE model is a proper candidate for dark energy.

Summary This paper presents a novel thermodynamically consistent constitutive model for partially saturated porous rocks across a wide range of conditions. The material states generated behind the shock wave from an explosive source can vary significantly, ranging from crushed and melted rock near the source to a poroelastic medium in the far field. In the model, rock strength is determined by the effective pressure, which is calculated using two independent equations of state: one for the solid rock and another for the pore fluid. The model accounts for shock-induced liquefaction resulting from fluid pressure buildup in the pore spaces near the explosive source. Simultaneously, it describes the increase in wave propagation speed due to elastic pore contraction in both dry and partially saturated rocks. This model is applied to investigate how fluid saturation affects the amplitude and shape of the generated waves, as well as the residual stress surrounding the cavity formed by spherical explosions.

Abstract Ideal gases adhere to the principles of the kinetic theory of gases. To illustrate their non-ideal characteristics, we derive the equation of state for the lattice gas model defined on a cubic lattice through mean-field theory (MFT). The central focus of this work is the introduction and application of hard-spin MFT (HS-MFT), which preserves the discrete nature of site occupancy (or equivalently, Ising spin variables) within a mean-field framework. The resulting equation of state contains a logarithmic term structurally similar to the Saha–Basu equation. While reproducing the standard mean-field result, HS-MFT yields a critical temperature significantly closer to Monte Carlo benchmarks and—crucially—correctly predicts the absence of a finite-temperature phase transition in one dimension, a well-known shortcoming of conventional mean-field treatments. We further analyze the critical point, critical exponents, law of corresponding states, Boyle temperature, Joule–Thomson coefficient, inversion temperature, and heat capacity relations derived from this equation of state. We believe that the progression from standard to HS-MFT offers students of statistical mechanics a richer, more physically consistent pathway to understanding phase transitions and non-ideal fluid behavior.

Abstract Dark energy (DE) models with many free parameters are often considered excessive, as constraining all parameters poses a significant challenge. While such models offer greater flexibility to probe the DE sector in more detail. With the rapid advancement of astronomical surveys and the availability of diverse datasets, it is timely to examine whether current combined observations can effectively constrain an extended parameter space in DE models. This article investigates a four-parameter dynamical DE model that spans a broad region of the Universe’s expansion history through four key parameters: present-day value of the DE equation of state ( w 0 ), its initial value ( w m ), scale factor depicting transition from w m to w 0 ( a t ), and steepness of this transition (Δ de ). We constrain the model using cosmic microwave background data from Planck, BAO from DESI DR2, and three distinct compilations of Type Ia Supernovae: PantheonPlus, DESY5, and Union3. Our results show that constraining all four parameters remains challenging: a t is not constrained by any dataset, constraints on w m and Δ de remain weak, only w 0 is well constrained across all datasets. The results further show that w 0 > −1, while w m is negative, indicating a phantom-like behavior at early times. Interestingly, despite its larger parameter space, the proposed model shows a preference over the ΛCDM and w 0 w a CDM scenarios for certain combined datasets, according to both Δ χ 2 and Bayesian evidence, although this preference is not strong.

Measurement models that have a chemical composition as one of the arguments require special attention when used with the law of propagation of uncertainty from the Guide to the expression of uncertainty in measurement. The constraint that the amount fractions in a composition add exactly to unity not only affects the covariance matrix associated with the composition, but also impacts the differentiation of the measurement model to obtain the expressions and values of the sensitivity coefficients. Differentiating the measurement model with respect to each variable individually is not possible as it involves evaluating the model for infeasible inputs, leading to an undefined output. In this work, a numerical method for constrained partial differentiation is presented, enabling the use of the law of propagation of uncertainty for measurement models with compositions as one of their arguments. The numerical method enables treating the measurement model as a black box and using it with measurement models in the form of an algorithm. The numerical method is demonstrated by showing how the uncertainty associated with composition, temperature and pressure can be propagated through an equation of state, in this case, the GERG-2008 equation of state. It is shown that this differentiation can be completed in a few simple steps, requiring only a valid implementation of the measurement model that provides an output value for given input quantities. The numerical differentiation method applies in principle to all differentiable functions of a composition.

We study the inflationary gravitational wave background induced by Abelian gauge fields generated by non-minimal kinetic and axial couplings to the inflaton. We show that, up to slow-roll corrections, for coupling functions that share the same dependence on conformal time, the gravitational wave spectrum is nearly scale invariant. We also derive its amplitude for generic gauge field coupling parameters, within the slow-roll approximation. The coupling values and the scale of inflation for which the induced gravitational wave background is observable, while ensuring that back-reaction on the inflationary dynamics remains negligible, are calculated. We find that a sizeable axial coupling can boost this secondary gravitational wave signal above the standard inflationary background. In the course of our analysis, we also show how to analytically match tensor perturbations across an arbitrary number of eras with different equations of state.

We perform a comparative Bayesian analysis of fermionic and bosonic dark matter admixed neutron stars (DMANS) by incorporating a comprehensive set of theoretical, experimental, and astrophysical constraints. The hadronic matter equation of state (EoS) is modeled using a relativistic mean-field approach, constrained by chiral effective field theory (χEFT) calculations at low densities, finite nuclei and heavy-ion collision data at intermediate densities, and neutron star (NS) observations at high densities. For the dark sector, we consider fermionic dark matter (FDM) interacting via a dark vector meson, and two bosonic dark matter models (BDM1 and BDM2) characterized by self-interacting scalar fields. Bayesian inference is employed to constrain the model parameters, including the dark matter mass, coupling strength, and dark matter fraction within NSs. Our analysis finds that all models yield consistent nuclear matter parameters, allowing a small dark matter fraction under 10%. The presence of dark matter slightly softens the EoS, leading to a modest reduction in NS mass, radius, and tidal deformability, though all models remain compatible with NICER and GW170817 observations. The log-evidence and likelihood analyses reveal no statistical preference among the FDM and BDM models, indicating that current astrophysical data cannot decisively distinguish between fermionic and bosonic dark matter scenarios. This study provides a unified statistical framework to constrain dark matter properties using NS observables.

We investigate the impact of a hypothetical bosonic dark matter (DM) candidate, the sexaquark, on the fundamental (f-mode) oscillations of neutron stars (NSs). By varying the DM particle mass and considering different core compositions including hypernuclear matter, sexaquark DM, and deconfined quark matter (QM), we construct hybrid equations of state (EOS) with a smooth hadron-quark crossover that remain consistent with current astrophysical constraints on mass (M), radius (R), and tidal deformability (Λ). Our analysis shows that the presence of these exotic components systematically alters quasi-universal f-mode relations considering f-mode frequency (f), damping time (τ), compactness (C), and angular velocity (ω). In particular, relations involving f-√(M/R 3), (R 4/M 3 τ)(C), ω M(C), require higher-order polynomial fits compared to standard studies. Quadratic forms remain sufficient for f-√(M/R 3) and ω M(C), while damping-time relations such as (R 4/M 3τ)(C) demand higher-order corrections to capture their curvature. For f(Λ), a cubic fit provides a satisfactory description. Within this extended framework the relations remain tight and effectively composition independent. These results suggest that precise f-mode measurements with future gravitational-wave detectors could provide clear signatures of DM and other exotic matter in NS interiors.

When a turbulent Bose-Einstein condensate (BEC) is driven out-of-equilibrium at a scale much smaller than the system size, nonlinear wave interactions transfer particles towards large scales in an inverse cascade process. In this work, we numerically study wave turbulence in a three-dimensional BEC in forced and dissipative inverse cascade settings. We observe that when the forcing rate increases, thereby increasing the particle flux, the turbulence spectrum gradually transitions from the weak-wave Kolmogorov-Zakharov cascade to a critical balance state characterized by a range of scales with balanced linear and nonlinear dynamic timescales. Further forcing increases lead to a coherent condensate component superimposed with Bogoliubov-type acoustic turbulence. The role of vortices in such a strongly forced state is marginal, which makes this new state distinct from the strongly turbulent state composed of a tangle of quantized vortex lines. We then use our predictions and numerical data to formulate a new out-of-equilibrium equation of state for the 3D inverse cascade.

Tidal deformability and compactness of neutron stars and massive pulsars from semi-microscopic equations of state