Two-body entropy of two-dimensional fluids

Klumov, B. A.; Khrapak, S. A.

doi:10.1016/j.rinp.2020.103020

Cited by 20 publications

(8 citation statements)

References 35 publications

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“…The excess entropy is approximately equal to the two-body interaction entropy when we ignore the negligible higher-body interaction terms. Therefore, we used following formula to calculate the reduced excess entropy: − S ex / k normalB ≈ S 2 / k normalB = prefix− 2 π ρ ∫ 0 ∞ [ g false( r false) ln ⁡ g false( r false) − g false( r false) + 1 ] r 2 nobreak0em.25em⁡ normald r where k B is the Boltzmann constant and ρ is the number density. Also, g ( r ) is the radial density distribution (RDF) of the methanol component.…”

Section: Methodsmentioning

confidence: 99%

Detecting Liquid–Liquid Phase Separations Using Molecular Dynamics Simulations and Spectral Clustering

et al. 2023

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A stringent test of the accuracy of empirical force fields is reproducing the phase diagram of bulk phases and mixtures. Exploring the phase diagram of mixtures requires the detection of phase boundaries and critical points. In contrast to most solid–liquid transitions, in which a global order parameter (average density) can be used to discriminate between two phases, some demixing transitions entail relatively subtle changes in the local environment of each molecule. In such cases, finite sampling errors and finite-size effects make the identification of trends in local order parameters extremely challenging. Here we analyze one such example, namely a methanol/hexane mixture, and compute several local and global structural properties. We simulate the system at various temperatures and study the structural changes associated with demixing. We show that despite a seemingly continuous transformation between mixed and demixed states, the topological properties of the H-bond network change abruptly as the system crosses the demixing line. In particular, by using spectral clustering, we show that the distribution of cluster sizes develops a fat tail (as expected from percolation theory) in the vicinity of the critical point. We illustrate a simple criterion to identify this behavior, which results from the emergence of large system-spanning clusters from a collection of aggregates. We further tested the spectral clustering analysis on a Lennard–Jones system as a standard example of a system with no H-bonds, and also, in this case, we were able to detect the demixing transition.

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Section: Methodsmentioning

confidence: 99%

Detecting Liquid–Liquid Phase Separations Using Molecular Dynamics Simulations and Spectral Clustering

et al. 2023

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“…where v T = T /m is the thermal velocity and m is the atomic mass. A somewhat different variant of entropy scaling of atomic diffusion in condensed matter was also proposed by Dzugutov [14], who used the excess entropy in the pair approximation instead of the full excess entropy (note that the total excess entropy can be approximated by the pair contribution only in some vicinity of the freezing point [15][16][17][18][19][20][21]). By now it is well recognized that many simple and not so simple systems conform to the approximate excess entropy scaling.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Excess entropy determines the applicability of Stokes-Einstein relation in simple fluids

Khrapak,

Khrapak

2021

Preprint

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The Stokes-Einstein (SE) relation between the self-diffusion and shear viscosity coefficients operates in sufficiently dense liquids not too far from the liquid-solid phase transition. By considering four simple model systems with very different pairwise interaction potentials (Lennard-Jones, Coulomb, Debye-Hückel or screened Coulomb, and the hard sphere limit) we identify where exactly on the respective phase diagrams the SE relation holds. It appears that the reduced excess entropy sex can be used as a suitable indicator of the validity of the SE relation. In all cases considered the onset of SE relation validity occurs at approximately sex −2. In addition, we demonstrate that the line separating gas-like and liquid-like fluid behaviours on the phase diagram is roughly characterized by sex −1.

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“…In the last decade, researchers have increased their attention on two-dimensional Yukawa systems [1][2][3][4][5][6][7][8][9]. Firstly, this is due to the fact that such systems can be easily implemented in experiments.…”

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confidence: 99%

Calculation of Thermodynamic Characteristics and Sound Velocity for Two-Dimensional Yukawa Fluids Based on a Two-Step Approximation for the Radial Distribution Function

Fairushin

Мокшин

2023

Fluids

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We propose a simple two-step approximation for the radial distribution function of a one-component two-dimensional Yukawa fluid. This approximation is specified by the key parameters of the system: coupling parameter and screening parameter. On the basis of this approximation, analytical expressions are obtained for the same thermodynamic quantities as internal energy, internal pressure, excess entropy in the two-particle approximation, and also longitudinal sound velocity. The theoretical results show an agreement with the results obtained in the case of a true radial distribution function.

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Two-body entropy of two-dimensional fluids

Cited by 20 publications

References 35 publications

Detecting Liquid–Liquid Phase Separations Using Molecular Dynamics Simulations and Spectral Clustering

Detecting Liquid–Liquid Phase Separations Using Molecular Dynamics Simulations and Spectral Clustering

Excess entropy determines the applicability of Stokes-Einstein relation in simple fluids

Calculation of Thermodynamic Characteristics and Sound Velocity for Two-Dimensional Yukawa Fluids Based on a Two-Step Approximation for the Radial Distribution Function

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