Representation Of Phase Diagram Research Articles

Phase Behavior of System Carbon Dioxide + Hydrogen Sulfide

The global phase equilibrium behavior of the CO2+H2S system is discussed in this work for temperatures ranging from 160 K up to the critical region. Solid phases of CO2 and H2S and corresponding equilibria have been modeled by considering either a 4th-order equation of state (also used for the fluid phases) or a solid fugacity model for the pure components combined with an activity coefficient model (both coupled with a reference equation of state for the fluid phases).Phase equilibrium calculations have been performed by the minimization of the Gibbs Free Energy of mixing and compared to existing literature data.The types of pressure-mole fraction phase diagrams that can be encountered in the low-temperature thermodynamic region have been described. The temperature and pressure ranges where the phase behavior of the system changes have been identified and a representative phase diagram is presented for each range.

Emerging solutions from the battle of defensive alliances

Competing strategies in an evolutionary game model, or species in a biosystem, can easily form a larger unit which protects them from the invasion of an external actor. Such a defensive alliance may have two, three, four or even more members. But how effective can be such formation against an alternative group composed by other competitors? To address this question we study a minimal model where a two-member and a four-member alliances fight in a symmetric and balanced way. By presenting representative phase diagrams, we systematically explore the whole parameter range which characterizes the inner dynamics of the alliances and the intensity of their interactions. The group formed by a pair, who can exchange their neighboring positions, prevail in the majority of the parameter region. The rival quartet can only win if their inner cyclic invasion rate is significant while the mixing rate of the pair is extremely low. At specific parameter values, when neither of the alliances is strong enough, new four-member solutions emerge where a rock-paper-scissors-like trio is extended by the other member of the pair. These new solutions coexist hence all six competitors can survive. The evolutionary process is accompanied by serious finite-size effects which can be mitigated by appropriately chosen prepared initial states.

Consistent thermodynamic modeling of H2O–HCl–KOH–KCl between 200 K and 1,000 K

Over the last few decades, thermochemical databases for aqueous solutions and for high-temperature salt solutions have been developed separately from each other. This is largely due to the fact that the models used for the liquid phases are inconsistent. However, there is interest in highly concentrated aqueous solutions, as well as in the hydrolysis of salt melts, closing the gap between the two communities. Here, the liquid phase was consistently modeled, covering the complete composition space between H2O, HCl, KOH, and KCl at temperatures between 200 K and 1,000 K. Thermodynamic modeling of phase equilibria in the KCl–K2O–HCl–H2O reciprocal system was carried out using an associate solution model for the liquid phase, spanning from water to pure liquid acid and base, and liquid salt. Using the Calphad technique, the H2O–KCl, H2O–HCl, H2O–K2O, and KOH–KCl binary systems were critically assessed. While the model does not cover classical aqueous thermochemical properties (pH and osmotic coefficient), an excellent representation of phase diagrams and heat of reactions was achieved.

Study on the volatility of four benzaldehydes

This work reports the experimental determination of relevant thermodynamic properties of four benzaldehydes. The vapor pressures of both crystalline and liquid phases (including supercooled liquid) of syringaldehyde, 3,4,5-trimethoxybenzaldehyde, 4-(dimethylamino)benzaldehyde and of the liquid phase of veratraldehyde were determined using a static method based on capacitance diaphragm manometers. Additionally, the sublimation vapor pressures of the four compounds were also determined at different temperatures, using the Knudsen mass-loss effusion method. The experimental results allowed accurate determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation and of vaporization for the benzaldehydes studied, at reference temperatures, allowing phase diagram representations of the (p,T) results, in the neighborhood of the triple point of the four compounds. Their temperatures and molar enthalpies of fusion were determined using differential scanning calorimetry and were compared with the ones obtained indirectly through vapor pressure measurements. Using high-precision drop calorimetry, the standard isobaric molar heat capacities of the four crystalline benzaldehydes were determined at 298.15 K. The enthalpy of the intermolecular hydrogen bond OH…O in the crystalline phase of syringaldehyde was estimated.

Wake transitions and steady -instability of an Ahmed body in varying flow conditions

The paper investigates experimentally the flow past a flat-back, taller than wide Ahmed body having rectangular base aspect ratio $H/W=1.11$ in the context of ground vehicle aerodynamics. Parametric studies at Reynolds number $2.1\times 10^5$ explore the sensitivity of the aerodynamic force and body pressure distribution with respect to varying flow conditions defined from variable ground clearance $C$ (taken at mid-distance from the front and rear axles of the body), pitch angle $\alpha$ , and yaw angle $\beta$ (equivalent to a crosswind). Two-dimensional parametric maps in the parametric spaces $(\beta,C)$ and $(\beta,\alpha )$ are obtained for parameter ranges covering real road vehicle driving conditions. The study of the base pressure gradient reveals non-trivial and sharp transitions identified as significant changes of near wake orientation in both parametric spaces. All unsteady transitions correspond to fluctuation crises of the vertical gradient component only. These transitions are summarized in phase diagram representations. Both phase diagrams in $(\beta,C)$ and $(\beta,\alpha )$ parametric spaces can be unified at large yaw in the $(\beta,C_r)$ space, where the rear clearance $C_r$ separating the lower edge of the base from the ground is a simple function of the pitch $\alpha$ and the clearance $C$ . The impacts of the wake transitions are clearly identified in the base drag, drag, lift and side force coefficients. The contribution of the steady near wake $z$ -instability (Grandemange et al., Phys. Fluids, vol. 25, 2013a, pp. 95–103) is assessed by repeating the sensitivity analysis with a rear cavity. As reported previously, the rear cavity suppresses the steady instability by symmetrizing the wake. A domain for the existence of the instability is finally proposed in the attitudes map $(\beta,\alpha )$ defined from regions where the mean lateral force coefficients are significantly decreased by the presence of the rear cavity. In addition, it is found that the steady instability forces the wake to be less unsteady for all attitudes that do not correspond to unsteady transitions.

Superconducting dome and pseudogap endpoint in Bi2201

Once doped away from their parent Mott insulating state, the hole-doped cuprates enter into many varied and exotic phases. The onset temperature of each phase is then plotted versus $p$---the number of doped holes per copper atom---to form a representative phase diagram. Apart from differences in the absolute temperature scales among the various families, the resultant phase diagrams are strikingly similar. In particular, the $p$ values corresponding to optimal doping (${p}^{\mathrm{opt}}\ensuremath{\sim}0.16$) and to the end of the pseudogap phase $({p}^{*}\ensuremath{\sim}0.19--0.20)$ are essentially the same for all cuprate families bar one: the single-layer Bi-based cuprate ${\mathrm{Bi}}_{2+z\ensuremath{-}y}{\mathrm{Pb}}_{y}{\mathrm{Sr}}_{2\ensuremath{-}x\ensuremath{-}z}{\mathrm{La}}_{x}{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ (Bi2201). This anomaly arises partly due to the complex stoichiometry of this material and also to the different $p$ values inferred from disparate (e.g., bulk or surface) measurements performed on samples with comparable superconducting transition temperatures ${T}_{c}$. Here, by combining measurements of the in-plane resistivity in zero and high magnetic fields with angle-resolved photoemission spectroscopy studies in the superconducting and normal state, we argue that the phase diagram of Bi2201 may in fact be similar to that realized in other families. This study therefore brings Bi2201 into the fold and supports the notion of universality of ${p}^{\mathrm{opt}}$ and ${p}^{*}$ in all hole-doped cuprates.

Thermodynamic Stability of Fenclorim and Clopyralid.

The present work reports an experimental thermodynamic study of two nitrogen heterocyclic organic compounds, fenclorim and clopyralid, that have been used as herbicides. The sublimation vapor pressures of fenclorim (4,6-dichloro-2-phenylpyrimidine) and of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were measured, at different temperatures, using a Knudsen mass-loss effusion technique. The vapor pressures of both crystalline and liquid (including supercooled liquid) phases of fenclorim were also determined using a static method based on capacitance diaphragm manometers. The experimental results enabled accurate determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation for both compounds and of vaporization for fenclorim, allowing a phase diagram representation of the (p,T) results, in the neighborhood of the triple point of this compound. The temperatures and molar enthalpies of fusion of the two compounds studied were determined using differential scanning calorimetry. The standard isobaric molar heat capacities of the two crystalline compounds were determined at 298.15 K, using drop calorimetry. The gas phase thermodynamic properties of the two compounds were estimated through ab initio calculations, at the G3(MP2)//B3LYP level, and their thermodynamic stability was evaluated in the gaseous and crystalline phases, considering the calculated values of the standard Gibbs energies of formation, at 298.15 K. All these data, together with other physical and chemical properties, will be useful to predict the mobility and environmental distribution of these two compounds.

Thermodynamic modeling and phase diagram prediction of salt lake brine systems II. Aqueous Li+-Na+-K+-SO42− and its subsystems

Predicted result of complete structure phase diagram of Li 2 SO 4 -Na 2 SO 4 -H 2 O system at temperature ranging from eutectic point 251.19–373.15 K: P1, P2, P3, P4, P5 are Transition points of three solid co-saturated in the ternary system. • Thermodynamic model of aqueous Li+-Na+-K+-SO 4 2− systems across entire temperature range. • Predicting the polythermal full structure phase diagram of ternary and quaternary aqueous system.. • The multi-objective optimization method to obtain solid constants and liquid parameters. It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component, multi-temperature and high concentration. The essential subsystem of sulfate type brine, aqueous Li + -Na + -K + -SO 4 2− and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model. Liquid parameters ( Δ g IJ , Δ h IJ , and Δ C p , I J ) associated with the contributions of Gibbs energy, enthalpy, and heat capacity to the binary interaction parameters, i . e . the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression, are determined via multi-objective optimization method. The solid constants Δ f G k ° ( 298.15 ) and Δ f H k ° ( 298.15 ) of 11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities. The modeling results show the accurate representation of (1) solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K; (2) isothermal phase diagrams for Li 2 SO 4 -Na 2 SO 4 -H 2 O, Li 2 SO 4 -K 2 SO 4 -H 2 O and Na 2 SO 4 -K 2 SO 4 -H 2 O ternary systems. The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.

Discussion upon the Stationarity and the Causality of a Time Series Using the Phase Diagram Representation

Discussion upon the Stationarity and the Causality of a Time Series Using the Phase Diagram Representation

Electron Holography and Magnetotransport Measurements Reveal Stabilized Magnetic Skyrmions in Fe1-xCoxSi Nanowires.

Magnetic skyrmions are topological spin textures that have shown promise for future nonvolatile memory devices. Herein, we report on the stability of magnetic skyrmions in alloyed cubic B20 Fe1-xCoxSi nanowires (NWs) determined using off-axis electron holography and magnetotransport measurements. This study presents the real space observation of one-dimensional skyrmion lattice in a NW of Fe1-xCoxSi which shows that the skyrmion phase in a Fe0.75Co0.25Si NW exists at lower applied magnetic fields (200 Oe) with a reduced domain size (28 ± 2 nm) in comparison to bulk and thin film samples. Magnetotransport measurements were used to observe the helimagnetic transition temperature dependence on the cobalt concentration in the Fe1-xCoxSi NWs. Field-dependent magnetoresistance measurements of Fe1-xCoxSi NWs underappliedmagnetic field parallel to the NW axisand their second derivative plots reveal the critical fields for the magnetic state transition at different temperatures. A representative magnetic phase diagram constructed with the results from transport measurements of a Fe0.81Co0.19Si NW clearly shows expanded stability region for magnetic skyrmions in the Fe1-xCoxSi NWs.

Phase Diagram-Based Sensing with Adaptive Waveform Design and Recurrent States Quantification for the Instantaneous Frequency Law Tracking.

Monitoring highly dynamic environments is a difficult task when the changes within the systems require high speed monitoring systems. An active sensing system has to solve the problem of overlapped responses coming from different parts of the surveyed environment. Thus, the need of a new representation space which separates the overlapped responses, is mandatory. This paper describes two new concepts for high speed active sensing systems. On the emitter side, we propose a phase-space-based waveform design that presents a unique shape in the phase space, which can be easily converted into a real signal. We call it phase space lobe. The instantaneous frequency (IF) law of the emitted signal is found inside the time series. The main advantage of this new concept is its capability to generate several distinct signals, non-orthogonal in the time/frequency domain but orthogonal within the representation space, namely the phase diagram. On the receiver side, the IF law information is estimated in the phase diagram representation domain by quantifying the recurrent states of the system. This waveform design technique gives the possibility to develop the high speed sensing methods, adapted for monitoring complex dynamic phenomena In our paper, as an applicative context, we consider the problem of estimating the time of flight in an dynamic acoustic environment. In this context, we show through experimental trials that our approach provides three times more accurate estimation of time of flight than spectrogram based technique. This very good accuracy comes from the capability of our approach to generate separable IF law components as well as from the quantification in phase diagram, both of them being the key element of our approach for high speed sensing.

Dynamical system analysis of a five-dimensional cosmological model

A five-dimensional cosmological model including a single perfect fluid is studied in the framework of dynamical system analysis. All the critical points of the system with their stability properties are listed and some representative phase diagrams are explicitly shown. It is found that the stabilization of the extra dimension is possible and the observed flatness of the three-dimensional space is provided for certain ranges of the equation of state parameter of the fluid during the evolution of the universe. The model suggested here can be considered as a simplified model for examining the possible effects of the extra dimensions in the early universe.

К дискуссии по вопросам представления равновесной фазовой диаграммы Fe-Ni и природы инварного эффекта

К дискуссии по вопросам представления равновесной фазовой диаграммы Fe-Ni и природы инварного эффекта

Phase equilibria of phenolic compounds in water or ethanol

The mutual solubilities of water and eight phenolic compounds (i.e. phenol, guaiacol, syringol, pyrocatechol, o-, m-, p-cresol and vanillin) were investigated between 293.15 and 323.15K. The solubility of the phenolic compounds in water increases as follows: vanillin < syringol < guaiacol < p-cresol < m-cresol < o-cresol < phenol < pyrocatechol. For the molecules presenting liquid-liquid equilibria, the solubility of water into the phenolic phase increases as follows: guaiacol < o-cresol < m-cresol < p-cresol < syringol. The vapor-liquid equilibria of binary mixtures composed of ethanol and phenol or guaiacol or o-cresol were measured in a range of pressure from 0.09 bar to atmospheric pressure. Finally, the mixing enthalpies of the phenolic compounds with ethanol indicate that the reactions are exothermic. It was found that NRTL model is suitable for the representation of phase diagrams of systems containing phenolic compounds and water or ethanol.

Phase behavior of system methane + hydrogen sulfide

An accurate description of the phase behavior of the CH4 + H2S system is given for temperatures from 70 K to the critical temperature of H2S and pressures up to 250 MPa. The study includes the solid phases of CH4 and H2S. A global pressure‐temperature diagram is presented. The types of temperature‐composition and pressure‐composition phase diagrams that can be encountered in the studied temperature and pressure ranges have been described. The temperature and pressure ranges where the phase behavior of the system changes have been identified and a representative phase diagram is presented for each range. Phase diagrams have been obtained through the solid–liquid–vapor equation of state proposed by Yokozeki. The parameters of the equation of state have been regressed on all the available phase equilibrium data for the considered system. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4090–4108, 2016

Thermodynamic study of nicotinamide, N-methylnicotinamide and N,N-dimethylnicotinamide: Vapour pressures, phase diagrams, and hydrogen bonds

Using the Knudsen-effusion method and/or a diaphragm manometer static method, the vapour pressures of the condensed phases (crystalline and liquid) of nicotinamide, N-methylnicotinamide and N,N-dimethylnicotinamide were measured, respectively, over the following temperatures ranges (341.2 to 433.7)K, (329.2 to 426.6)K and (308.2 to 370.5)K. The experimental results enabled the determination of the standard molar enthalpies, entropies and Gibbs free energies of sublimation and of vaporisation, at T=298.15K, as well as phase diagram representations of the (p,T) experimental results, including the triple point, for the three compounds studied. The temperatures and molar enthalpies of fusion were determined using differential scanning calorimetry and were compared with the values derived indirectly from the vapour pressure measurements. The enthalpy of the intermolecular hydrogen bonds N−H…O present in crystalline N-methylnicotinamide was calculated and the sum of the enthalpies of the intermolecular hydrogen bonds N−H⋯O and N−H⋯N, [ΔHB(N−H⋯O)H+ΔHB(N−H⋯N)H], formed in the crystalline phase of nicotinamide was also estimated.

Thermodynamic properties of the methyl esters of p-hydroxy and p-methoxy benzoic acids

The vapor pressures of crystalline and liquid phases of methyl p-hydroxybenzoate and of methyl p-methoxybenzoate were measured over the temperature ranges (338.9 to 423.7)K and (292.0 to 355.7)K respectively, using a static method based on diaphragm capacitance gauges. The vapor pressures of the crystalline phase of the former compound were also measured in the temperature range (323.1 to 345.2)K using a Knudsen mass-loss effusion technique. The results enabled the determination of the standard molar enthalpies, entropies and Gibbs free energies of sublimation and of vaporization, at T=298.15K, as well as phase diagram representations of the (p,T) experimental data, including the triple point. The temperatures and molar enthalpies of fusion of both compounds were determined using differential scanning calorimetry and were compared with the results indirectly derived from the vapor pressure measurements. The standard (p°=105Pa) molar enthalpies of formation, in the crystalline phase, at T=298.15K, of the compounds studied were derived from their standard massic energies of combustion measured by static-bomb combustion calorimetry. From the experimental results, the standard molar enthalpies of formation, in the gaseous phase at T=298.15K, were calculated and compared with the values estimated by employing quantum chemical computational calculations. A good agreement between experimental and theoretical results is observed. To analyze the thermodynamic stability of the two compounds studied, the standard Gibbs free energies of formation in crystalline and gaseous phases were undertaken. The standard molar enthalpies of formation of the title compounds were also estimated from two different computational approaches using density functional theory-based B3LYP and the multilevel G3 methodologies.

Reprint of: Crystalline and liquid vapour pressures of the four p-monohalophenols: A thermodynamic study of their phase transitions

Vapour pressures of condensed phases of p-monohalophenols were measured over the temperature ranges (265.6 to 342.8)K, (273.5 to 331.0)K, (285.3 to 370.5)K and (307.2 to 380.4)K, respectively for p-fluoro, p-chloro, p-bromo and p-iodophenol, using a static method based on diaphragm capacitance gauges. The results obtained for each compound, enabled the determination of the standard molar enthalpies, Gibbs energies and entropies of sublimation and of vaporisation, at T=298.15K as well as phase diagram representations of the (p,T) experimental results. The temperatures and molar enthalpies of fusion were determined using DSC and were compared with the values derived from the vapour pressure measurements. Correlations involving thermodynamic properties and also the volume of the halogen substituent of p-halophenols are presented and compared to the ones derived before for related methyl p-halobenzoates and p-halobenzoic acids. Vapour pressures, at T=298.15K, of the compounds included in the three families are well described by a single correlation based on the temperature of fusion and on the volume of the halogen atom.

Analytical representation of phase diagrams

Analytical representation of phase diagrams

Application of the SLV-EoS for representing phase equilibria of binary Lennard–Jones mixtures including solid phases

In 2003, Yokozeki proposed an equation of state capable of representing solid, liquid, and vapor phases. This equation represents an innovative approach of including solid in phase diagrams. The capability of this equation of state, named SLV-EoS, of giving a qualitative correct representation of phase diagrams for binary mixtures of Lennard–Jones spheres has been tested in this work. The SLV-EoS has been used for producing the phase diagrams of binary Lennard–Jones mixtures with diameter ratio σ11/σ22 ranging from 0.85 to 1, and well-depth ratio ɛ11/ɛ22 ranging from 0.625 to 1.6 at reduced pressure P*=Pσ113/ε11=0.002. The obtained phase diagrams have been compared with literature data obtained by Monte-Carlo simulation. The comparison shows the incapability of the SLV-EoS with null binary interaction parameters of predicting solid–liquid azeotrope and eutectic in the investigated range of σ11/σ22 and ɛ11/ɛ22. Binary interaction parameters have been regressed to allow the SLV-EoS giving a qualitative representation of the three types of phase diagrams: solid solution, solid azeotrope and simple eutectic. Binary interaction parameters are shown being smoothed functions of σ11/σ22 and ɛ11/ɛ22, allowing the prediction of the phase behavior for other Lennard–Jones mixtures or real mixtures of simple fluids.