Thermodynamic Behavior of Fluids Near the Critical Point

Sengers, J. V.

doi:10.1146/annurev.pc.37.100186.001201

Cited by 658 publications

(277 citation statements)

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“…The thermodynamics of a system in the critical region is dominated by the presence of long-range density fluctuations. As a consequence, the thermodynamic surface of fluids exhibits a singularity at the critical point which can be described in terms of non-analytical scaling laws with universal critical exponents and universal scaling functions [100,101]. All classical, analytical equation of state mentioned above fail to reproduce the singular behavior of fluids and fluid mixtures in the critical and supercritical regions.…”

Section: Crossover Modelsmentioning

confidence: 99%

Thermodynamic Properties of Methanol in the Critical and Supercritical Regions

et al. 2005

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The isochoric heat capacity of pure methanol in the temperature range from 482 to 533 K, at near-critical densities between 274.87 and 331.59 kg · m −3 , has been measured by using a high-temperature and high-pressure nearly constant volume adiabatic calorimeter. The measurements were performed in the singleand two-phase regions including along the coexistence curve. Uncertainties of the isochoric heat capacity measurements are estimated to be within 2%. The single-and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from experimental data for each measured isochore. The critical temperature (T c = 512.78 ± 0.02 K) and the critical density (ρ c = 277.49 ± 2 kg · m −3 ) for pure methanol were derived from the isochoric heat-capacity measurements by using the well-established method of quasi-static thermograms. The results of the C V V T measurements together with recent new experimental PVT data for pure methanol were used to develop a thermodynamically self-consistent Helmholtz free-energy parametric crossover model, CREOS97-04. The accuracy of the crossover model was confirmed by a comprehensive comparison with available experimental data for pure methanol and values calculated with various multiparameter equations of state and correlations. In the critical and supercritical regions at 0.98T c T 1.5T c and in the density range 0.35ρ c ρ 1.65ρ c , CREOS97-04 represents all available experimental thermodynamic data for pure methanol to within their experimental uncertainties.

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Section: Crossover Modelsmentioning

confidence: 99%

Thermodynamic Properties of Methanol in the Critical and Supercritical Regions

et al. 2005

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“…Simulations of finite systems in the canonical ensemble results in an overestimate of the critical temperature (or an underestimate for an LCST). The results of GEMC simulations can be treated as "experimental data" and analyzed using the ideas of universal critical exponents and corrections to scaling [32]. The liquid-liquid phase transition exhibited by the square-well mixture belongs to the three-dimensional Ising-type universality class.…”

Section: Fig 1 (A)mentioning

confidence: 99%

“…Renormalization group theory leads to scaling laws for critical phenomena which can be used to correct for the behavior away from the asymptotic critical region [33]. The resulting expansion for the mole fraction can be written as an expansion in the departure from the critical temperature t 1 2 T ͞T c as [27,32]:…”

Section: Fig 1 (A)mentioning

confidence: 99%

Simulation Study of the Link between Molecular Association and Reentrant Miscibility for a Mixture of Molecules with Directional Interactions

1999

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The reentrant liquid-liquid miscibility of a symmetrical mixture with highly directional bonding interactions is studied by Gibbs ensemble Monte Carlo simulation. The resulting closed loop of immiscibility and the corresponding lower critical solution temperature are shown to be a direct consequence of the dramatic increase in association between unlike components as the temperature is lowered. Our exact calculations for an off-lattice system with a well-defined anisotropic potential confirm the findings of previous theoretical studies. [S0031-9007(99) PACS numbers: 61.20.Qg, 05.20.Jj Reentrant phase behavior is one of the most characteristic and beguiling signatures of hydrogen bonding in simple and complex fluids alike. The so-called closedloop liquid-liquid immiscibility found in a wide variety of fluid mixtures is a common example of the relationship between hydrogen-bonding association and reentrant behavior: here the region of liquid-liquid immiscibility is bounded above and below by upper and lower critical solution temperatures (UCST and LCST) (see Refs. [1,2] for general reviews). Closed-loop immiscibility was first reported for the nicotine-water mixture at the turn of the 20th Century [3]. Other well-known examples of this type of reentrant behavior include aqueous solutions of butan-2-ol [4], alkylpyridines [5], and alkylpolyoxyethylene nonionic surfactants [6], as well as a number of polymer solutions [7,8]. The common feature of these systems is the possibility of hydrogen bonding between the two components of the mixture. An increase in temperature overcomes the unfavorable enthalpic contribution (incompatibility of the two components) leading to miscibility above the UCST. The low-temperature miscibility below the LCST can be explained in terms of hydrogen bonding between unlike components which becomes the dominant feature of the free energy of the system, and results in a favorable heat of solution. One should note that in the case of polymer solutions the principal feature responsible for the LCST is the large difference in size between the polymer molecule and the solvent.Hirshfelder et al. [9] were the first to suggest directional attractive forces as a direct cause of the LCST. This view is supported by the theoretical predictions of Barker and Fock [10], who analyzed a simple lattice model with interactions that depend on the relative orientations of the molecules using the Bethe-Guggenheim quasichemical approximation; an appropriate choice of parameters for the unlike directional interactions gives rise to closedloop behavior. A more rigorous treatment of similar lattice models, using appropriate decoration transformations to the equivalent Ising models of ferromagnets [11] or alternatively using the Migdal-Kadanoff approximations of renormalization group (RG) theory [12], has also been applied to study closed-loop immiscibility in systems with highly asymmetrical interactions (e.g., see Refs. [13][14][15][16][17][18]). The results of the more recent calculations are in reasonable q...

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“…15 The resulting critical-temperature values were then used, along with the law of rectilinear diameters, 16,17 to determine the critical density, ρ c , of each compound. Representative plots of eqn 5 for the perfluoroalkanes are shown in Fig 4(a), while the corresponding L-V phase envelopes are shown in Fig 4(b).…”

Section: Resultsmentioning

confidence: 99%

Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation

Amat

2010

The Journal of Chemical Physics

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A molecular-dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region.Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached. 2

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Thermodynamic Behavior of Fluids Near the Critical Point

Cited by 658 publications

References 0 publications

Thermodynamic Properties of Methanol in the Critical and Supercritical Regions

Thermodynamic Properties of Methanol in the Critical and Supercritical Regions

Simulation Study of the Link between Molecular Association and Reentrant Miscibility for a Mixture of Molecules with Directional Interactions

Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation

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