Critical Point Parameters Research Articles

Configuration entropy and thermodynamics phase transition of black hole in [formula omitted] gravity

Starting from a d−dimensional black hole (BH) in f(R) gravity, we analyzed the effect of modified gravity on critical point parameters, the difference in number densities, and configuration entropy during the BH phase transition phenomenon. From our investigations, consistent results with charged AdS BH are obtained that is holographic dual of van der Waal’s fluid and hence the BH in modified gravity. The thermodynamic pressure, temperature, and free energy are affected by f(R) gravity. The difference in the number densities of molecules (small and large BHs) and configuration entropy are investigated as a function of reduced temperature (τ̃). The difference in the number densities of BH molecules in f(R) gravity decreases with the increase in τ̃, whereas, Scon increases monotonically and becomes a concave function with the increase in space–time dimensions. The relation between the difference in the number density of BH molecules and space–time dimensions (d) decreases with the increase in dimension d. Finally, using our results, the laws of BH Physics are also discussed.

Solubility of o-toluidine in supercritical carbon dioxide at high-temperatures and high-pressures

In many technological applications the solubility (VLE data) of materials (solid or liquids) in SC CO2 is required. It is essential to understand the solubility and other properties of o-toluidine in the SC CO2 due to their technological importance. This paper presents a new isothermal VLE data for SC CO2 (1)+ o-toluidine (2). Thus, the main purpose of the present work is to experimental study of the VLE properties (solubility, PTxy relationship) of o-toluidine (one of the technologically important compound) in the SC CO2 needs for variety industrial applications. The measurements were made at four selected isotherms of (313.15, 333.15, 353.15, and 373.15) K over the pressure range from (1.24 to 31.44) MPa. A high-temperature and high-pressure optical cell has been used to measure of the phase equilibrium properties (PTxy) of the binary CO2 (1)+ o-toluidine (2) mixture. The combined expanded absolute and relative uncertainty of the temperature, pressure, and the phase concentration measurements at 0.95 confidence level with a coverage factor of k = 2 is estimated at 0.15 K, 0.2 %, and 3 %, respectively. The critical point parameters of the mixture in the PC−TC projection have been estimated using the measured VLE data. The shape of the critical curve behavior indicates that CO2 (1) + o-toluidine (2) mixture belongs to the Type III according to the Konynenburg and Scott classification. PR and PC-SAFT equation of state (EoS) were successfully applied to model the phase equilibria (qualitative point of view) for the SC CO2 (1) + o-toluidine (2) mixture at the measured experimental temperatures. From a quantitative point of view, the best choice (among the models used) was PR EoS. The critical curves predicted with PR and PC-SAFT EoS confirmed that the mixture is classified as Type III phase behavior.

Theoretical investigation on regulating photophysical properties and proton transfer behavior by electronegativity for near-infrared emitting styryl dyes.

Our main focus is to explore the atomic electronegativity-dependent photoinduced behavior of styryl derivatives (HBO, HBS, and HBSe). The results of structural parameter calculation by the DFT method show that the intramolecular hydrogen bonds of normal and tautomer form are strengthened and weakened, respectively, in an excited state (S1), which is conducive to the excited intramolecular proton transfer (ESIPT) process. The enhancement of excited hydrogen bond is beneficial to the ESIPT process from the aspects of infrared vibration frequency (IR), Mulliken's charge analysis, and density gradient reduction (RDG). Additionally, by determining the bond energy with the band critical point (BCP) parameter, we found that the lower the electronegativity of the atom, the larger the hydrogen bond strength at the excited state and the more likely ESIPT reaction occurs. Meanwhile, the intramolecular H-bonds O-H…N in HBO, HBS, and HBSe are enhanced with the weakened electron-withdrawing capacity of the atom (from O to S and Se). Subsequently, frontier molecular orbital (FMOs) and charge density difference (CDD) analyses essentially revealed that electron redistribution induces the ESIPT process. Low atomic electronegativity exhibits the high chemical activity of the excited state. Furthermore, to demonstrate the electronegativity-dependent ESIPT behavior of the system, we built potential energy curves (PECs) and located the transition states (TS) of proton transfer processes.

Thermodynamic Quantities of Morse Fluids in the Supercritical Region

The critical point parameters for liquid alkali metals (sodium and potassium) are calculated accounting for the non-Gaussian order parameter fluctuations and the Morse interaction potential. The behavior of the isothermal compressibility, density fluctuations, and thermal expansion for sodium is studied in the supercritical temperature region. A significant increase in the isothermal compressibility and the density fluctuations near the critical point indicates a substantial density sensitivity to tiny pressure fluctuations. The thermal expansion coefficient for various fixed pressure values shows a typical gas decrease with increasing supercritical temperature. The Widom line separating the gaseous and liquid structures of the fluid at temperatures above the critical one is represented. Note that our calculations are valid in a small neighborhood of the critical point, which is problematic for theoretical and experimental studies.

THE USE OF THE НАССР SYSTEM IN THE PRODUCTION OF MEAT PRODUCTS WITH CHLORELLA MICROALGAE

In the 21st century, the lack of protein and important nutrients in the diet has become a pressing issue for humanity, prompting scientists around the world to look for alternatives and develop new food products. At the same time, the government is actively pursuing a policy that protects consumers from low-quality and unsafe food. One of these tools is the introduction of the HACCP food safety management system at food companies, which is a preventive method of preventing the negative impact of hazardous factors on the human body and the spread of food-related diseases. In this aspect, attention is focused on the hazards that can affect meat pates using the microalgae Chlorella during the cooking process. Chlorella contains macro- and micro-nutrients that are essential for the proper functioning of the body. Chlorella microalgae was used in the form of a powder (food additive) and a Chlorella wellness drink Ukrainian-made. All stages of the process were analysed, and potential hazards, causes or sources of pollution were considered at each stage. In the process of identifying risks, a risk analysis diagram and a decision tree diagram were used. The flowchart of the technological process of making meat pates with Chlorella was built. The parameters of control critical points (storage temperature of raw materials, finished products, temperature regimes of cooking) were determined, and critical limits were set for control critical points, the exceeding of which will lead to the emergence of biological hazards. For those process steps where it is impossible or impractical to measure parameters, we have defined precondition operating programs to manage hazards. The connection between preventive methods that affect safety and obtaining a food product with specified quality characteristics, which is the basis of the state policy of Ukraine in the field of healthy nutrition, where preserving and promoting public health is a priority, was established.

Generation IV Nuclear Reactor: Coolant Materials in the Supercritical State

On the basis of the generalized van der Waals equations of state, the quasispinodal and the supercritical-point parameters of the Generation IV nuclear reactor coolant materials, namely, sodium, lead and bismuth, have been determined. To improve accuracy, the known van der Waals equation of state has been generalized in three different ways. That is, the attractive term in the van der Waals equation of state has been modified by introducing new substance-specific parameters. The parameters of the generalized van der Waals equations of state have been determined through vapor-liquid critical-point parameters. The mean percentage error in the determined quasispinodal for sodium, lead, and bismuth is less than 3% in comparison with the Semenchenko correlation. T he temperature correlation of the quasispinodal pressure for sodium, lead, and bismuth, formulated in this work, is statistically excellent with the mean correlation coefficient of 0.99995 and the coefficient of determination of 0.999895. The mean supercritical-point parameters of sodium, lead, and bismuth, based on the three-parameter generalized van der Waals equations of state, are found to be (28.80 MPa, 15.1563 10−5 m3/mol, and 2563 K), (207.2275 MPa, 8.876 10−5 m3/mol, and 5278 K) and (155.338 MPa, 10.5923 10−5 m3/mol, and 4788 K) respectively. The generalized van der Waals equations of state are presented in the reduced form from which follows the law of corresponding states.

Criticality points on the phase diagram of substances as scaling parameters in the law of corresponding states: alkali metals

The law of corresponding states (LCS), based on a generalized van der Waals equation of state (gvdWEoS) has been formulated by rescaling its thermodynamic variables with liquid- vapour critical—point parameters, the spinodal, the thermodynamic limit of superheat (TLS) and the supercritical (SC) point. This gvdWEoS differs from the known van der Waals equation of state (vdWEoS) by the modified attractive term. The scaling properties have been derived on the basis of the gvdWEoS. The expressions for the isothermal compressibility, a derivate of Gibbs free energy, have been derived. In all the cases of rescaling, the gvdWEoS has the similar functional form and the expression for isothermal compressibility has a similar functional form. This shows that the parameters of any spinodal-point on the phase diagram, including the TLS as a particular case, and the SC point, characteristic point on the quasispinodal, provide the alternate scales of parameterizing the thermodynamic properties of substances other than the liquid-vapour critical point. Moreover, an isothermal compressibility regularity is formulated on the basis of the gvdWEoS and it is found to satisfactorily trace the literature data for saturated liquid alkali metals.

The external field effect on the opinion formation based on the majority rule and the q-voter models on the complete graph

We investigate the external field effect on opinion formation based on the majority rule and [Formula: see text]-voter models on a complete graph. The external field can be considered as the mass media in the social system, with the probability [Formula: see text] agents following the mass media opinion. Based on our Monte Carlo simulation, the mass media effect is not strong enough to make the system reach a homogeneous state (complete consensus) with the magnetization [Formula: see text] for all values of [Formula: see text], indicating the existence of a usual phase transition for all values of [Formula: see text]. In the [Formula: see text]-voter model, the mass media eliminates the usual phase transition at [Formula: see text]. We obtain the model’s critical point and scaling parameters using the finite-size scaling analysis and obtain that both models have the same scaling parameters. The external field effect decreases both models’ relaxation time and the relaxation time following the power-law relation such as [Formula: see text], where [Formula: see text] is the population size and [Formula: see text] depends on the probability [Formula: see text]. In the majority rule model, [Formula: see text] follows a linear relation, and in the q-voter model, [Formula: see text] follows a power-law relation.

Unveiling the effects of atomic electronegativity on ESIPT behaviors for FQ-OH system: A theoretical study

In this work, we mainly focus on exploring the effects of atomic electronegativity on excited state intramolecular proton transfer (ESIPT) behavior for novel FQ-OH derivatives theoretically. Combining analyses of geometrical changes, infrared (IR) spectral variations, and bonding energies via band critical point (BCP) parameters, we clarify the excited state hydrogen bonding strength is enhancing with decrease of atomic electronegativity. In addition, photo-induced charge reorganization and different energy gap of momentous frontier molecular orbitals (MOs) further reflect intramolecular charge transfer (ICT) promotes ESIPT reaction. Low atomic electronegativity reveals excited state high kinetic dynamics and chemical activities. Via constructing potential energy curves (PECs) and searching transition state (TS), we clarify atomic electronegativity dependent ESIPT behavior for FQ-OH. Particularly, the modification of atomic electronegativity also plays critical roles in regulating UV–Vis spectra. This work not only uncovering detailed ESIPT mechanism for FQ-OH, but also presents a novel regulated mechanism via atomic electronegativity.

Substituent control of dynamical process for excited state intramolecular proton transfer of benzothiazole derivatives

Using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, in this work, the excited state intramolecular proton transfer (ESIPT) mechanisms of 2-(2′-hydroxyphenyl)benzothiazole (HBT) derivatives obtained by switching the ortho-position functional group of the hydroxyl group have been investigated. Analysis of bond parameters, bond energy, and infrared (IR) vibrational spectra show that hydrogen bonds are enhanced in the first excited state. The core-valence bifurcation (CVB) index and bond critical point (BCP) parameters are further applied to evaluate hydrogen bonds. The maximum absorption and emission peaks of molecules mainly originate from the transition of electrons from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). Exploring potential energy curves (PECs) and transition state (TS) energy profiles, we clarify the ultrafast ESIPT behavior of HBT and its derivatives are easier in the excited state. It is clarified that the HBT derivatives in the excited state with electron withdrawing group at the ortho-position weaken the intramolecular hydrogen bond OH···N, while are not conducive to the ESIPT process. And the electronic effect of the substituents can be employed to adjust the emission of the fluorophore from blue to near-infrared. The calculated results also show that the enol form is stable in the ground state, while the keto form is the main conformation in the excited state.

Coherent Acoustic Phonon Oscillations and Transient Critical Point Parameters of Ge from Femtosecond Pump–Probe Ellipsometry

Herein, the complex pseudodielectric function of Ge and Si from femtosecond pump–probe spectroscopic ellipsometry with 267, 400, and 800 nm pump–pulse wavelengths is analyzed by fitting analytical lineshapes to the second derivatives of the pseudodielectric function with respect to energy. This yields the critical point parameters (threshold energy, lifetime broadening, amplitude, and excitonic phase angle) of and in Ge and in Si as functions of delay time. Coherent longitudinal acoustic phonon oscillations with a period of about 11 ps are observed in the transient critical point parameters of Ge. From the amplitude of these oscillations, the laser‐induced strain is found to be on the order of 0.03% for Ge measured with the 800 nm pump pulse, which is in reasonable agreement with the strain calculated from theory.

Thermalhydraulic comparison of supercritical fluids in minichannel heat sink to assess the suitability of macroscopic scaling rules

Suitability of supercritical fluids as heat transport media in mini-/microscale has not been explored much, despite showing enormous potential in macrochannels. One major hindrance thereof is the absence of scaling rules devised specifically for such scales. Present numerical study explores the thermalhydraulic characteristics of five different supercritical fluids, identified based on the diversity in their respective critical-point parameters, for a particular minichannel employing a conventional set of scaling relations. Supercritical fluids exhibit consistently-superior heat transfer coefficient compared to single-phase, and even boiling, channels. Substantial level of similarity has been observed in the visual nature of the dimensionless momentum and thermal fields and local recirculation patterns across the fluids, as a consequence of the imposed scaling. Noticeable difference, however, exists in characterizing dimensionless groups, such as local Reynolds number and local and area-averaged Nusselt number, pointing toward the deficiency of the scaling model. R134a can be earmarked as the optimum fluid among the considered ones, both in terms of Nusselt number and dimensionless pressure drop, though it experiences the largest entropy generation as well. It is suggested to consider the profiles of Prandtl number and dimensionless thermal conductivity with dimensionless enthalpy for improving the used scaling rules.

Theoretical insights into effects of solvent polarity on excited‐state N–H proton transfer behavior for a new fluorophore of 3‐tosylamino‐N‐cyclohexylphthalimide

AbstractCompared with O–H···O‐type system, the N–H···O‐type system with excited‐state intramolecular proton transfer (ESIPT) provides a better research object for exploring kinetics and thermodynamics because the existence of amino group can be replaced by various groups. In this work, the ESIPT mechanism of a novel amino type proton donor (3TsAPI) has been studied, and its effects of solvent polarity have been investigated. We optimize the structures of 3TsAPI using density functional theory (DFT)/time‐dependent density functional theory (TDDFT) methods, and electronic spectra data are consistent with the experiment. Through the analyses of structural parameters and spectra related to hydrogen bonding, it is found hydrogen bonding is enhanced in S1 state, and analyses of bond critical point (BCP) parameters and core‐valence bifurcation (CVB) indexes show excited‐state hydrogen bonding is stronger in solvents with weaker polarity. We construct the potential energy curves and find polarity of solvents can regulate the potential energy barrier of ESIPT process and then further elucidate the ESIPT mechanism of 3TsAPI.

Электронная зонная структура, распределение зарядовой плотности и химическая связь в молекулярных кристаллах халькогенов

The electronic band structure and the charge density distribution are theoretically studied in rhombohedral and monoclinic selenium, rhombohedral and orthorhombic sulphur with the aim to classify types of chemical bonding in molecular crystals of chalcogens. It is found that valence s- and lower in energy p-electrons contribute mainly in covalent bonds between nearest neighboring atoms in ring-shaped molecules, while all types of valence p-electrons provide bonding between rings of atoms in crystals. Parameters of critical points and the character of the charge density distribution in their vicinity point to coexistence of a number of types of chemical bonding in molecular crystals of Se and S: covalent, semimetallic and one more type, characterizing by the charge density fluctuations. Van der Waals forces, being important for finding equilibrium lattice parameters, have little impact on the charge density distribution and on the chemical bonding in crystals of chalcogens.

Electronic band structure, charge density distribution and chemical bonding in molecular crystals of chalcogens

The electronic band structure and the charge density distribution are theoretically studied in rhombohedral and monoclinic selenium, rhombohedral and orthorhombic sulphur with the aim to classify types of chemical bonding in molecular crystals of chalcogens. It is found that valence s- and lower in energy p-electrons contribute mainly in covalent bonds between nearest neighboring atoms in ring-shaped molecules, while all types of valence p-electrons provide bonding between rings of atoms in crystals. Parameters of critical points and the character of the charge density distribution in their vicinity point to coexistence of a number of types of chemical bonding in molecular crystals of Se and S: covalent, semimetallic and one more type, characterizing by the charge density fluctuations. Van der Waals forces, being important for finding equilibrium lattice parameters, have little impact on the charge density distribution and on the chemical bonding in crystals of chalcogens. Keywords: chalcogens, molecular crystals, electronic band structure, types of chemical bonding.

Optical Properties of Magnesium-Zinc Oxide for Thin Film Photovoltaics.

Motivated by their utility in CdTe-based thin film photovoltaics (PV) devices, an investigation of thin films of the magnesium-zinc oxide (MgxZn1−xO or MZO) alloy system was undertaken applying spectroscopic ellipsometry (SE). Dominant wurtzite phase MZO thin films with Mg contents in the range 0 ≤ x ≤ 0.42 were deposited on room temperature soda lime glass (SLG) substrates by magnetron co-sputtering of MgO and ZnO targets followed by annealing. The complex dielectric functions ε of these films were determined and parameterized over the photon energy range from 0.73 to 6.5 eV using an analytical model consisting of two critical point (CP) oscillators. The CP parameters in this model are expressed as polynomial functions of the best fitting lowest CP energy or bandgap E0 = Eg, which in turn is a quadratic function of x. As functions of x, both the lowest energy CP broadening and the Urbach parameter show minima for x ~ 0.3, which corresponds to a bandgap of 3.65 eV. As a result, it is concluded that for this composition and bandgap, the MZO exhibits either a minimum concentration of defects in the bulk of the crystallites or a maximum in the grain size, an observation consistent with measured X-ray diffraction line broadenings. The parametric expression for ε developed here is expected to be useful in future mapping and through-the-glass SE analyses of partial and complete PV device structures incorporating MZO.

Thermophysical properties of liquid molybdenum in the near-critical region using quantum molecular dynamics

We present a comprehensive first-principles study of the thermophysical properties of liquid molybdenum in the near-critical region. The ab initio estimate of the molybdenum critical-point parameters is also provided. The robustness of our calculations is confirmed by the excellent agreement with available experiments on shock compression and the successive isentropic expansion of porous samples of molybdenum and several isobaric expansion experiments. We also analyze important thermodynamic properties such as the isochoric and isobaric heat capacity, the Gr\"uneisen parameter, and the speed of sound of liquid molybdenum along the critical isobar up to the critical point.

Scaling of Phase Diagram and Critical Point Parameters in Liquid-Vapour Phase Transition of Metallic Fluids

The first objective of this paper is to investigate the scaling behavior of liquid-vapor phase transition in FCC and BCCmetals starting from the zero-temperature four-parameter formula for cohesive energy. The effective potentials between the atoms in the solid are determined while using lattice inversion techniques as a function of scaling variables in the four-parameter formula. These potentials are split into repulsive and attractive parts, as per the Weeks–Chandler–Anderson prescription, and used in the coupling-parameter expansion for solving the Ornstein–Zernike equation that was supplemented with an accurate closure. Thermodynamic quantities obtained via the correlation functions are used in order to obtain critical point parameters and liquid-vapor phase diagrams. Their dependence on the scaling variables in the cohesive energy formula are also determined. An equally important second objective of the paper is to revisit coupling parameter expansion for solving the Ornstein–Zernike equation. The Newton–Armijo non-linear solver and Krylov-space based linear solvers are employed in this regard. These methods generate a robust algorithm that can be used to span the entire fluid region, except very low temperatures. The accuracy of the method is established by comparing the phase diagrams with those that were obtained via computer simulation. The avoidance of the ’no-solution-region’ of the Ornstein-Zernike equation in coupling-parameter expansion is also discussed. Details of the method and complete algorithm provided here would make this technique more accessible to researchers investigating the thermodynamic properties of one component fluids.

Estimation of the Critical Point Parameters of the Liquid–Vapor Phase Transition of Metals Using Experiments on the Isentropic Expansion of Shock-Compressed Porous Samples

The isentropic expansion of shock-compressed porous metals (Cu, W, Nb) are experimentally studied, and the experimental results are used to determine their thermodynamic parameters and electrical conductivity. These results allow us to conclude that some porous metals after shock compression and expansion have a two-phase structure. The presence of an additional phase at the isentropic expansion of these metals significantly changes the character of evaporation and the critical point parameters of the liquid–vapor phase transition that are estimated using experiments on the isentropic expansion of shock-compressed porous metals. In addition, the formation of the two-phase structure explains the large difference between the critical point parameters estimated by different methods for a large group of metals (U, W, V, Co, Mo, Ta, etc.).

Superheating Limit of Hydrocarbons Based on a Generalized Dieterici Equation of State

A new three-parameter Dieterici type equation of state is employed for studying the high-temperature thermodynamic characteristics of hydrocarbons. This generalized equation of state differs from the known Dieterici equation of state by a modified attractive term. That is, a new thermodynamic similarity parameter is introduced in the attractive term of the Dieterici equation of state. The parameters of the equation of state are determined through the experimental values on the critical-point parameters of hydrocarbons. The equation of state is presented in the reduced form, from which follows the single-parameter law of corresponding states. The proposed equation of state gives the value of maximum attainable superheat for hydrocarbons of about 0.887 to 0.894 times the critical temperature. The new three- parameter generalized Dieterici equation of state offers an acceptable compliance with experimental results of maximum attainable superheat of hydrocarbons.