Pressure-energy correlations in liquids. I. Results from computer simulations

Bailey, Nicholas P.; Pedersen, Ulf R.; Gnan, Nicoletta; Schrøder, Thomas B.; Dyre, Jeppe C.

doi:10.1063/1.2982247

Cited by 232 publications

(314 citation statements)

References 25 publications

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“…Two state points (1) and (2) with temperatures T 1 and T 2 and densities ρ 1 and ρ 2 , respectively, are defined to be isomorphic (Paper IV) if they obey the following: any two physically relevant configurations of state points (1) and (2), r (1) 1 , . .…”

Section: A Definitionmentioning

confidence: 99%

“…The procedure applied to generate isomorphs can be summarized as: (1) an equilibrium N V T simulation was performed at a given state point; (2) γ was calculated from the fluctuations using Eq. (9); (3) the density ρ was changed slightly (of order 1%), and γ was used to calculate the corresponding change in temperature in order to keep S ex constant (Eq.…”

Section: Generating Isomorphs In Simulationsmentioning

confidence: 99%

“…This is the final paper in a series [1][2][3][4] investigating the properties of strongly correlating liquids, 5 i.e., liquids that have strong correlations between their constant-volume equilibrium fluctuations of potential energy, U (t), and virial 6,7 W (t) ≡ −1/3 i r i · ∇ r i U (r 1 , ..., r N ) where r i is the position of particle i at time t. As is well known, the average virial W gives the configurational contribution to the pressure:…”

Section: Introductionmentioning

confidence: 99%

“…[28][29][30] Paper I 1 presented computer simulations of 13 different systems, showing that van der Waals type liquids are strongly correlating, whereas hydrogen-bonding liquids like methanol or water are not. Strongly correlating liquids include, 1,2,5,22,29 for instance, the standard Lennard-Jones (LJ) liquid, the Kob-Andersen binary LJ (KABLJ) mixture, an asymmetric rigid-bond dumbbell model, a seven-site united-atom toluene model, and the Lewis-Wahnström OTP model.…”

Section: Introductionmentioning

confidence: 99%

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Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems

Schrøder

Gnan

Pedersen

et al. 2011

The Journal of Chemical Physics

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114

115

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This series of papers is devoted to identifying and explaining the properties of strongly correlating liquids, i.e., liquids with more than 90% correlation between their virial W and potential energy U fluctuations in the N V T ensemble. Paper IV [N. Gnan et al., J. Chem. Phys. 131, 234504 (2009)] showed that strongly correlating liquids have "isomorphs," which are curves in the phase diagram along which structure, dynamics, and some thermodynamic properties are invariant in reduced units. In the present paper, using the fact that reduced-unit radial distribution functions are isomorph invariant, we derive an expression for the shapes of isomorphs in the WU phase diagram of generalized Lennard-Jones systems of one or more types of particles. The isomorph shape depends only on the Lennard-Jones exponents; thus all isomorphs of standard Lennard-Jones systems (with exponents 12 and 6) can be scaled onto a single curve. Two applications are given. One tests the prediction that the solid-liquid coexistence curve follows an isomorph by comparing to recent simulations by Ahmed and Sadus [J. Chem. Phys. 131, 174504 (2009)]. Excellent agreement is found on the liquid side of the coexistence curve, whereas the agreement is less convincing on the solid side. A second application is the derivation of an approximate equation of state for generalized Lennard-Jones systems by combining the isomorph theory with the Rosenfeld-Tarazona expression for the temperature dependence of the potential energy on isochores. It is shown that the new equation of state agrees well with simulations.

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Section: A Definitionmentioning

confidence: 99%

Section: Generating Isomorphs In Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems

Schrøder

Gnan

Pedersen

et al. 2011

The Journal of Chemical Physics

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114

115

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“…At any given state point the Pearson correlation coefficient R for the NVT thermal equilibrium fluctuations of U and W measures the strength of the correlations. Only inverse power-law fluids are perfectly correlating (R = 1), but many models 47 , e.g., the Lennard-Jones liquid, and some experimental liquids 49 have been shown to belong to the class of Roskilde-simple liquids defined by requiring R ≥ 0.90 47 . This class appears to include most or all van der Waals and metallic liquids, but exclude most or all covalently, hydrogenbonding, or strongly ionic or dipolar liquids 47 .…”

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confidence: 99%

Predicting How Nanoconfinement Changes the Relaxation Time of a Supercooled Liquid

et al. 2013

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The properties of nanoconfined fluids can be strikingly different from those of bulk liquids. A basic unanswered question is whether the equilibrium and dynamic consequences of confinement are related to each other in a simple way. We study this question by simulation of a liquid comprising asymmetric dumbbell-shaped molecules, which can be deeply supercooled without crystallizing. We find that the dimensionless structural relaxation times − spanning six decades as a function of temperature, density, and degree of confinement − collapse when plotted versus excess entropy. The data also collapse when plotted versus excess isochoric heat capacity, a behaviour that follows from the existence of isomorphs in the bulk and confined states.That confined liquids microscopically relax and flow with different characteristic time scales than bulk liquids is hardly surprising. Confining boundaries bias the spatial distribution of the constituent molecules and the ways by which those molecules can dynamically rearrange. These effects play important roles in the design of coating, nanopatterning, and nanomanufacturing technologies 1,2 . As a result, they have already been experimentally characterized for a wide variety of material systems, including small-molecule fluids 3-10 , polymers 11-16 , ionic liquids 17 , liquid crystals 18 , and dense colloidal suspensions [19][20][21][22][23] , and studied extensively via molecular simulations 22,24-31 . Recent reviews of confined-liquid behavior may be found in, e.g., Refs. 10,32 .Unfortunately, successful theories for predicting the dynamics of inhomogeneous fluids have been slower to emerge. Here, we explore the possibility of a novel approach for predicting how confinement affects the dynamics of viscous fluids. The central idea is motivated by the observation from molecular simulations that, under equilibrium conditions, key dimensionless "reduced" quantities for confined fluids closely correspond to those of homogeneous bulk fluids with the same excess entropy 33-37 (relative to an ideal gas at the same density and temperature). The excess entropy can be computed using Monte Carlo methods 36 or predicted from classical density-functional theories 35,38 . An open question is whether this observed correspondence between dynamics and excess entropy applies for fluids in deeply supercooled liquid states approaching the glass transition, where highly nontrivial dynamic effects of confinement are observed. Another open question is whether thermodynamic properties other than the excess entropy can be used to predict the dynamics in confinement.To investigate these questions we study the behavior of a glass-former comprising asymmetric dumbbell-shaped molecules 39 . This model is perhaps the simplest singlecomponent system that avoids freezing upon cooling or compression in confinement, allowing for a systematic comparison of the properties of supercooled states in both bulk and confined geometries. The latter is modeled as a slit-pore, i.e., a sandwich geometry, using a 9-3 LennardJo...

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Scaling of Lennard–Jones liquid elastic moduli, viscoelasticity and other properties along fluid–solid coexistence

Heyes

Dini

Brańka

2015

Physica Status Solidi (b)

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Static and dynamical properties of the Lennard-Jones (LJ) fluid along the fluid-solid coexistence line are determined by Molecular Dynamics simulation. A number of properties, such as the radial distribution function, Einstein frequency, mean force, root mean square force, and normalized time correlation functions are shown to be essentially invariant or structurally isomorphic along this line when scaled by so-called macroscopic variables (MRU). Other quantities subject to MRU such as the potential energy, pressure and infinite frequency compressional modulus are not constant along this line of states but can be reproduced using simple formulae of the form for Roskilde fluids. The elastic moduli fall within the domain of isomorphism theory. A generalized Cauchy relationship in which the infinite frequency longitudinal modulus is proportional to the longitudinal modulus of the fluid was found to be obeyed very well for the LJ fluid phase along this coexistence line.

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Pressure-energy correlations in liquids. I. Results from computer simulations

Cited by 232 publications

References 25 publications

Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems

Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems

Predicting How Nanoconfinement Changes the Relaxation Time of a Supercooled Liquid

Scaling of Lennard–Jones liquid elastic moduli, viscoelasticity and other properties along fluid–solid coexistence

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