Similarity law for Widom lines and coexistence lines

Banuti, Daniel T.; Raju, Muralikrishna; Ihme, Matthias

doi:10.1103/physreve.95.052120

Cited by 63 publications

(37 citation statements)

References 29 publications

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“…For van der Waals Argon, c V is constant, therefore Widom anomaly does not exist for this quantity. Detailed description about the relation of Widom lines and coexistence lines of different species were given by Banuti et al [21].…”

Section: Methodsmentioning

confidence: 99%

Anomalous Properties of Some Fluids − with High Relevance in Energy Engineering − in Their Pseudo-critical (Widom) Region

Imre

Groniewsky

Györke

et al. 2019

Period. Polytech. Chem. Eng.

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Recent results are shown about the peculiarities of the pseudo-critical region, with special emphasis on properties important for energy production and conversion. The property-map of some materials, which are relevant as model fluids or as working / cooling fluids in energy engineering (argon, methane, water and carbon dioxide) and their relative positions to various adiabats – influencing their stability through the anomalous properties – are presented. Some potential technological problems related to the existence of these anomalies are discussed.

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Section: Methodsmentioning

confidence: 99%

Anomalous Properties of Some Fluids − with High Relevance in Energy Engineering − in Their Pseudo-critical (Widom) Region

Imre

Groniewsky

Györke

et al. 2019

Period. Polytech. Chem. Eng.

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“…G.G.Simeoni et al [8] carried out inelastic X-ray scattering and molecular dynamics simulation to find out a demarcation line between two dynamically different regime ("liquidlike" and "gaslike") in supercritical fluid around critical point called Widom line. In a recent study, however, it has been found that this Widom line doesn't obey the corresponding states principle and the transition lines differ with different fluids [9]. Few years back, the discovery of Frenkel line in the phase diagram further adds to the * kankaghosh@physics.iitm.ac.in.…”

Section: Introductionmentioning

confidence: 99%

Structural behavior of supercritical fluids under confinement

Ghosh

Krishnamurthy

2018

Phys. Rev. E

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The existence of the Frenkel line in the supercritical regime of a Lennard-Jones (LJ) fluid shown through molecular dynamics (MD) simulations initially and later corroborated by experiments on argon opens up possibilities of understanding the structure and dynamics of supercritical fluids in general and of the Frenkel line in particular. The location of the Frenkel line, which demarcates two distinct physical states, liquidlike and gaslike within the supercritical regime, has been established through MD simulations of the velocity autocorrelation (VACF) and radial distribution function (RDF). We, in this article, explore the changes in the structural features of supercritical LJ fluid under partial confinement using atomistic walls. The study is carried out across the Frenkel line through a series of MD simulations considering a set of thermodynamics states in the supercritical regime (P=5000 bar, 240K≤T≤1500K) of argon well above the critical point. Confinement is partial, with atomistic walls located normal to z and extending to "infinity" along the x and y directions. In the "liquidlike" regime of the supercritical phase, particles are found to be distributed in distinct layers along the z axis with layer spacing less than one atomic diameter and the lateral RDF showing amorphous-like structure for specific spacings (packing frustration) and non-amorphous-like structure for other spacings. Increasing the rigidity of the atomistic walls is found to lead to stronger layering and increased structural order. For confinement with reflective walls, layers are found to form with one atomic diameter spacing and the lateral RDF showing close-packed structure for the smaller confinements. Translational order parameter and excess entropy assessment confirms the ordering taking place for atomistic wall and reflective wall confinements. In the "gaslike" regime of the supercritical phase, particle distribution along the spacing and the lateral RDF exhibit features not significantly different from that due to normal gas regime. The heterogeneity across the Frenkel line, found to be present both in bulk and confined systems, might cause the breakdown of the universal scaling between structure and dynamics of fluids necessitating the determination of a unique relationship between them.

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“…As a reference line, we use the supercritical gas-liquid boundary (SGLB), defined as the loci of equal liquid and gas fractions, π gas = π liq = 0.5, in the supercritical domain (T > T c ). Taking the SGLB, which is also the line of maximal instability, as a reference is based on two observations: (i) near the LGCP, the Widom line and the SGLB closely coincide 16 , and (ii) the vapor-liquid equilibrium line (VLE), the LGCP, and the Widom line can be framed together within an extended corresponding states principle 20 . Therefore, we employ the postulate that the SGLB is the extension of the VLE and LGCP into the supercritical region 2/10 The phase diagram of the order parameter π gas , as computed by the machine learning classifiers ( Fig.…”

Section: Main Textmentioning

confidence: 99%

Universality, Scaling, and Collapse in Supercritical Fluids

Yoon

Tlusty

et al. 2019

J. Phys. Chem. Lett.

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Supercritical fluid (SCF) is known to exhibit salient dynamic and thermodynamic crossovers and an inhomogeneous molecular distribution. However, the question as to what basic physics underlies these microscopic and macroscopic anomalies remains open. Here, using an order parameter extracted by machine learning, the fraction of gas-like (or liquid-like) molecules, we find simplicity and universality in SCF: First, all isotherms of a given fluid collapse onto a single master curve described by a scaling relation. The observed power law holds from the high-temperature and -pressure regime down to the critical point where it diverges. Second, phase diagrams of different compounds collapse onto their master curves by the same scaling exponent, thereby demonstrating a putative law of corresponding supercritical states in simple fluids. The reported results support a model of the SCF as a mixture of two interchangeable microstates, whose spatiotemporal dynamics gives rise to unique macroscopic properties.

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Similarity law for Widom lines and coexistence lines

Cited by 63 publications

References 29 publications

Anomalous Properties of Some Fluids − with High Relevance in Energy Engineering − in Their Pseudo-critical (Widom) Region

Anomalous Properties of Some Fluids − with High Relevance in Energy Engineering − in Their Pseudo-critical (Widom) Region

Structural behavior of supercritical fluids under confinement

Universality, Scaling, and Collapse in Supercritical Fluids

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